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QUALITY OF POULTRY PRODUCTS:

POULTRY MEAT

Spelderholt Jubilee Symposia

Doorwerth, May 1991

\\4

Other volumes in this series

II. Eggs and Egg Products

III. Safety and Marketing Aspects

The symposia were organised by:

Working Groups 4 and 5 of the European Federation of the World's

Poultry Science Association

and

Committee on Jubilee Symposia on the occasion of the 70th Anniversary

of the Spelderholt Centre for Poultry Research and Information Services

Beekbergen, The Netherlands

Members : R.W.A.W. Mulder

A. Oosterwoud

T.G. Uijttenboogaart

C.H. Veerkamp

A.W. de Vries

The editors want to thank Mrs. D. Veiner for her valuable secretarial

work in the preparation of these proceedings.

QUALITY OF POULTRY PRODUCTS

I. POULTRY MEAT

Proceedings of the 10th European Symposium on

the Quality of Poultry Meat held at

Parkhotel "De Branding", Doorwerth, May 12 - 17, 1991

edited by

T.G. Uijttenboogaart

C.H. Veerkamp

1991

Spelderholt Centre for Poultry Research

and Information Services,

Beekbergen, The Netherlands

Spelderholt Centre for Poultry Research and

Information Services, Agricultural Research Service (DLO)

7361 DA Beekbergen, The Netherlands

telephone: +31 -5766 6111

telefax : +31 - 5766 3250

Published 1991

ISBN 90-71463-42-7

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or

transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or

otherwise, without the prior written permission of the publisher.

No responsibility is assumed by the Publisher for any injury and/or damage to persons or property as a

matter of products liability, negligence or otherwise, or from any use or operation of any methods,

products, instructions or ideas contained in the material herein.

This publication can be ordered by remittance of the appropriate sum to : Bankaccount 4377.59.407 of

the AMRO-bank, Beekbergen, The Netherlands.

Volume I. Poultry Meat DFL 70

Volume II. Eggs and Egg Products DFL 60

Volume III. Safety and Marketing Aspects DFL 70.

The order should mention the volume and name of the publication.

Printed in The Netherlands

Ponsen & Looijen, Wageningen

INTRODUCTION

In 1975 the 2nd Symposium on Quality of Poultry Meat was organised for the first time by Spelderholt Poultry Research Institute. The Spelderholt Symposia are organized for the second time in 10 years now. The 10th Symposium on the Quality of Poultry Meat and the 4th Symposium on the Quality of Eggs and Egg Products are jointly organized. Like in 1981, the Symposia are part of celebration activities at Spelderholt: the 70th Anniversary of Spelderholt Centre for Poultry Research and Information Services. Research at Spelderholt Centre covers all areas of poultry production and processing. The actual subjects, hygiene, marketing new technologies, new products and alternative uses of meat and egg, as included in the symposium programme are among the priority research areas of the Spelderholt Centre. The three volumes of the Proceedings "Quality of Poultry Products" include all oral and poster presentations of the Symposia. This Volume I. "Poultry Meat" contains the contributions of the sessions on Quality of Poultry Meat. Symposia enhance the exchange of results of research and the personal contacts between participants from many countries. We therefore thank the members of the Working Groups on the Quality of Poultry Meat and on the Quality of Eggs and Egg Products of the European Branch of the World's Poultry Science Association to accept our offer to host these symposia.

Beekbergen, May 1991

Financial support for the symposia was generously given by the following companies and association.

Main sponsors:

Association of Dutch Egg Processors ANEVEI, Zeist Meyn B.V., Oostzaan Stork PMT B.V., Boxmeer

Sponsors:

Cehave N.V., Veghel - Mengvoederindustrie FPS, Food Processing Systems, Aalten Henkel Nederland B.V., Nieuwegein Lohmann Holland B.V., Vaassen Johnson Food Equipment, Doesburg Linco Benelux B.V., Veenendaal Misset International, Doetinchem Systemate Holland B.V., Numansdorp

CONTENTS

Page

INTRODUCTION 1

CONTENTS 3

Session Ml: Processing and meat quality

Fletcher, D.L 11 Ante mortem factors related to meat quality

Uijttenboogaart, T.G 21 Post mortem factors and poultry meat quality

Lindholst, S 31 Stunning and meat quality

Fries, R 33 Occurrence and judgement of characteristics in the poultry meat inspection

Hillebrand, S.J.W., M. van der Leun, F.J.M. Smulders and P.A. Koolmees 45 Glycolytic rate and sensory quality of Turkey M. pectoralis superficialis - Physical-chemical and morphological muscle characteristics

Kroon, J.J.A 55 Quality inspection in The Netherlands

Mohan Raj, A.B. and N. Gregory 59 Carcass and meat quality of gas stunned broilers

Schreurs, F.J.G 69 An immunological method to asses proteolytic breakdown of desmin, a structural myofibrillar protein, in broiler breast meat

Page

Veerkamp, C.H., C. Pieterse, N.M. Bolder and L.A.J.T. van Lith 79 Model experiments for cleaning broiler carcasses during scalding

Session M2: New uses for meat components

Ball, H.R., J.G. Akamittath 89 Improving the function and quality of mechanically separated poultry meat

Kijowski, J., J. Stangierski and A. Niewiarowicz 99 Conditions of isolation of chicken "surimi" from mechanically deboned meat and its freezing

Deursen, J.M.J, van 107 Production of further processed poultry meat products and its ingredients

Lemmers, H.A.M I l l The use of dairy ingredients in further processed poultry products

Kijowski, J 123 Modification of myofibrillar proteins in spent hen meat with phosphates in the presence of Sodium Chloride

Kijowski, J., A. Niewiarowicz and J. Pikul 131 Yield, quality and texture of "surimi" with or without connective tissue of chicken and spent hen mechanically deboned meat

Kopeé, W. and T. Smolinska 139 The effect of ionic strength and pyrophosphate on protein extraction and texture of sausages from chicken muscles

Page

Mfkovâ, K., L. Havlfkovâ and R. Benovsky 149 Oxidative changes of mechanically deboned poultry meat lipid components during storage

Skrabka-Blotnicka, T 159 The evaluation of light hen and broiler meat for production of highly comminuted sausages

Trziszka, T., A.K. Popiel and B. Kulpa 167 Washing procedure to remove fat and colour components from mechanically deboned turkey meat

Trziszka, T., T.G. Uijttenboogaart and F.J.G. Schreurs 177 Use of Na2C03/NaHC03 buffer for the extraction of myofibrillar proteins from MDPM and the influence of freezing on the functional properties of the isolates

Session M3: Methods for measuring quality criteria

Froning, G.W 191 Methods for measuring functional properties of poultry meat

Erdész, S.H.V., S. Erdész and F.J. Jankóné 201 Functional properties of poultry meat, possibilities for measuring water-binding capacity

Grashorn, M.A. and P. Komender 207 Real-time ultrasonic scanning for the estimation of breast muscle weight in chicken

Huyghebaert, G., J.L. de Boever and G. de Groote 215 Nutritional and genetic effects on carcass fat in broilers, with emphasis of NIRS for quality control

Kooij-Krijgsman, M. and C.H. Veerkamp 223 Carcass weight and ultrasonics to select broilers for breast meat yield

Page

Migineishvili, A 235 Criteria of selection for higher broiler chicken breast yield

Steverink, A.T.G 243 Near-Infrared Spectroscopy (MRS) and (poultry) meat analysis

Session M4: Factors related to product quality

Lynn, N.J., S.A. Tucker and T.S. Bray 251 Litter condition and contact dermatitis in broiler chickens

Bilgili, S.F., W.H. Revington, E.T. Moran, Jr. and R.D. Bushong 263 The influence of diet and stocking density on carcass quality of broilers processed under soft-and hard-scald conditions

Holsheimer, J.P 273 Nutrition and product quality

Hulan, H.W 289 Incorporating omega-3 fatty acid into chicken product lipids

Moran jr, E.T., N. Acar, W.H. Revington and S.F. Bilgili 303 Quality of broilers for fast-food deep-fat frying: Effects of strain, sex, live production procedure and location in flock population

El-Deek, A.A., M.A. Kosba, M. Farghaly and Y. Afifi 313 Performance of laying pullets fed different levels of cotton seed oil at various ages

Page

Pingel, H., R. Klemm and U. Knust 325 Improvement of the quality of duck meat

Ricard, F.H., G. Marché and M.J. Petitjean 333 Age and sex influences on slaughter and meat yields in pheasants

Ristic, M 339 Quality of poultry meat in various European countries

Swierczewska, E., J. Niemiec and J. Mroczek 347 Influence of rapeseed products on broiler performance and meat quality

Session M5: Automation and process control

Veerkamp, C.H 355 Automation and proces control in poultry processing plants

Obdam, J 365 A processors view on automation

Beeftink, J.W 371 Logistics - plant design and equipment -

Hupkes, H 377 Flexible automation: Transport of individual shackles

Sjollema, J. and P.C.F. Borsboom 383 In-line color measurements of broiler breast meat

Daley, W.R., J.C. Thompson and J.C. Wyvill 393 Color vision for poultry inspection and grading

INDEX OF CONTRIBUTORS

SESSION Ml

PROCESSING AND MEAT QUALITY

10

ANTE MORTEM FACTORS RELATED TO MEAT QUALITY

D.L. Fletcher

Department of Poultry Science, University of Georgia, Athens, GA 30602 USA

Abstract

It is well established that antemortem factors affect poultry meat quality. It has been generally assumed that long term production factors have more influence on meat quality than the short term factors just prior to slaughter. Short term factors such as feed withdrawal, handling, struggling and stunning are most often identified as those that affect antemortem glycogen depletion, rigor development and subsequent meat quality. The effects of short term physiological responses to stress on poultry meat quality are not as well documented as for red meat species. A review of literature on antemortem factors affecting poultry meat quality combined with recent laboratory evidence may indicate that physiological stress responses may be more important than previously thought.

Introduction

Antemortem factors affecting meat quality can be divided into short term and long term categories. Long term factors would include bird genetics, physiology, nutrition, management and disease. Short term factors would primarily be associated with those events that occur within the last 24 hours prior to death. These factors would include feed and water deprivation, catching, transport, holding, immobilization, stunning and killing. Numerous production and preslaughter factors have been identified as having an impact on either carcass or meat quality. Carcass quality factors being defined as conformation, appearance, color, physical damage and composition while meat factors would be associated with flavor, tenderness, appearance and stability. Often yield is included as a quality factor for both carcass and meat due to its economic importance. Examples of production factors associated with specific broiler carcass or meat quality attributes are summarized in Table 1. Meat quality attributes which have been shown to be affected by antemortem factors are appearance, flavor, texture, functional properties, stability and safety. Appearance would include such factors as muscle color, discoloration due to bruises, blood pooling, carotenoid deposition in the fat, myoglobin and hemoglobin reactions, surface reflectivity, and shape. Texture has been shown to be affected by activity, age, composition and struggle during slaughter. Meat functional properties, such as water holding and emulsification capacity, are primarily a function of post-mortem glycolytic reactions that affect meat pH. Stability and safety could be related to both chemical and microbial deterioration. In the context of this work, microbiological factors,

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regarding both stability and safety, are not included. Stability would therefor be concerned with lipid oxidation and enzymatic degradation, both of which have some antemortem connection. The effects of the long term production factors on carcass and meat quality are fairly well documented. Short term antemortem effects on meat quality are less well understood and documented. Least understood of all is the cumulative effect of antemortem stress on poultry meat quality. Of particular interest is evaluating the events of the last 24 h prior to processing on specific meat quality characteristics. Factors such as diet, feed and water deprivation, struggling, stunning and environmental conditions have all been shown to affect early rigor processes and subsequent meat quality.

Feed and water withdrawal

The effects of diet and feed withdrawal on meat quality have been investigated. It was recognized in other species that muscle carbohydrate reserves (glycogen) were depleted by combinations of starvation and antemortem activity. Murray and Rosenberg (1953) reported that chicken breast muscle glycogen content was the lowest following a 16 h fast (.05%) and increased to .33% following 1-10 h refeeding with cracked corn. Mellor et al. (1958) examined the role of muscle glycogen on muscle pH and texture. Birds classified with high glycogen concentration had an average final pH of 5.9 and shear value of 4.1. Birds grouped with an average glycogen concentration had a final pH of 6.2 and shear value of 5.6. Thus, the higher glycogen level was related to more tender meat. Birds fasted for 16 h without feed and water were found to have greater muscle glycogen stores than those given access to sugar supplemented feed and water during the 16 h prior to slaughter. Shrimpton (1960) reported that a 24 h feed withdrawal period resulted in reduced muscle glycogen at time of death, the amounts remaining in as little as 1 min post-slaughter were about the same (6.3 and 4.5 mg/g in full fed versus starved in fresh tissue, as opposed to 1.8 and 1.7 mg/g 1 min after slaughter, respectively). The pH was noted to fall faster in the full fed birds than in the fasted group. As opposed to deFremery and Pool (1960) in which the onset of rigor was between 2 and 4.5 h, Shrimpton (1960) found rigor to develop within 10 min, unless the birds have been specially starved. This difference, in part was attributed to method of slaughter in which the death struggle can deplete muscle glycogen stores very rapidly. The author concluded:

"...None of the factors known to be associated with the onset of rigor can there­fore be expected to have any substantial effect on the tenderness of meat from young chickens It is suggested, therefore, that if tough flesh is found on the carcasses of broilers, its presence is likely to be caused by adverse conditions during the life of the bird. The toughness may also be accentuated by bad practice in the packing station, but the changes associated with rigor seem likely to play only a small part in the development of toughness in the muscle of young chicken..."

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Babji et al. (1982a) examined the application of preslaughter dietary electrolyte treatment on carcass yields and turkey meat quality characteristics. Their work was predicated on the use of electrolytes for improving carcass yields and that they may help the bird to retain body fluids during preslaughter holding and could possibly reduce stress. They found no effect upon muscle pH, cooking loss, shear or water holding capacity. There results were similar with those of Hale and Stadelman (1973) and Riley et al. (1976) who found no positive effects of electrolyte treatment on overall processing yield or meat ten­derness of broilers.

Struggle, anesthesia and stunning

It was established that feed deprivation affects glycogen stores in the muscle at slaughter and thereby affects the speed and degree of rigor development affecting meat tenderness. It is also apparent that due to variations in glycogen results, factors associated with strug­gle during handling and slaughter were more critical. Numerous researchers have used various anesthesia and muscle poisons to evaluate the effects of free struggle and stunning on subsequent meat quality, often with highly contradictory results. Dodge and Stadelman (1960) examined the effects of struggling at time of death and the use of the tranquilizer "Tyzine" on meat tenderness at 2 or 5 hours postmortem. They reported that neither struggling nor the "Tyzine" had any significant effect on texture. Goodwin et al. (1961) reported that "humane" slaughter had no effect on breast meat tenderness but that the use of nembutal, electrical stunning and carbon dioxide stunning resulted in tougher dark meat. The effect of sodium pentobarbital supplied orally 1.5-3.5 h prior to slaughter on meat quality was examined by Stadelman and Wise, 1961. Birds receiving the sodium pento­barbital entered rigor slower, with less toughening for the first 2 h, but had an extended period of maximum toughness in which the anesthetized birds had greater shear from 3-12 h after which they were again more tender than the unanesthetized controls. DeFremery et al. (1962) reported that subcutaneous injections with adrenaline, intravenous injections with sodium iodoacetate or rapid cooking of the meat resulted in significantly more tender meat. They concluded that by prevention of post-mortem glycolysis with the adrenalin or iodoacetate or by cooking immediately postmortem that glycolyses causes toughness and the faster the glycolysis the greater the toughness. DeFremery (1965) re­ported that anesthetized birds took longer to enter rigor and had lower 24 h aged shear force values than nontreated and stunned birds. The untreated birds had the lowest initial glycogen values; stunned birds were intermediate. Struggling was minimized using a 3-4 min carbon dioxide gas prior to neck cutting (Klose et al., 1970). No other reference or specifics about the C02 stunning procedure was giv­en. Kahn and Nakamura (1970) reported that unrestrained struggle at slaughter resulted in tougher broiler breast meat. Minimizing postmortem glycolysis by epinephrine injection 5 h prior to slaughter resulted in broiler breast meat with the highest ultimate muscle pH and most tender meat. Epinephrine injected 2 h prior to slaughter resulted in a greater accumulation of lactic acid in the muscle, lower muscle pH and less tender meat.

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Landes et al. (1971) found that anesthetized turkeys (sodium pentobarbital) had slower postmortem pH decline, more tender meat following 72 h cold storage and freezing and increased protein extractability as compared to turkeys with no anesthesia at slaughter. The sodium pentobarbital was used to reduce the rate of postmortem glycolysis and slow the rate of pH decline. Free struggle at slaughter was compared to restrained slaughter (by use of killing cones) in turkey by Ma et al. (1971). Free struggle resulted in significantly shorter times to rigor completion, shorter contractility duration, greater excitability threshold and increased sarcomere lengthening at 2 h postmortem. It was concluded that struggle increased rigor development, increased development of toughness and increased the rate of tenderization. Ma and Addis (1973) reported that free struggle resulted in faster rigor completion, lower threshold voltage, increased contraction duration, higher muscle ATP concentration at 0 and 30 min postmortem, higher muscle pH values at 0, 15 and 30 min, and shorter sarco­mere lengths at 1 and 2 h postmortem. Free struggle had no effect on protein extractability, thaw loss, cook loss or shear value (5.7 for the struggle versus 4.7 for the cone restrained birds). Electrical stunning resulted in a longer time for rigor completion, lower threshold voltages, longer contraction duration and lower thaw loss than the free struggle birds. The authors stated that the lack of aerobic metabolism in pectoral muscle is an important factor.

The effects of death struggle on the biochemical metabolism of chicken breast meat was examined by Grey et al. (1974). They found that unrestrained slaughter resulted in a faster development of rigor than restrained birds or anaesthetized and overdosed control birds. All of the treatments were judged to have passed into rigor in the same pH range (6.13-6.25). Muscle removed within 3 min of slaughter did not enter rigor until 3-4 h postmortem. Wood and Richards (1975a) examined the effects of epinephrine injections from 0 to 24 h prior to slaughter on postmortem reactions in broiler breast meat. They found that epi­nephrine injection resulted in an increase muscle toughness, and increased rate of tension development, peaking at about 8 hours prior to slaughter and returning to normal after 24 h. Muscle glycogen decreased rapidly following injection but recovered to 50% of the initial level after 24 h. Females appeared to be more affected by the epinephrine for ATP and shear value. Free struggle during slaughter of turkeys was shown to result in significantly lower initial muscle pH, lower muscle glycogen, lower water holding capacity of the meat, higher shear, increased yield, greater redness (a) greater myoglobin and total pigments than anes­thetized controls (Ngoka et al., 1982). Feed withdrawal resulted in higher final muscle pH and higher meat water holding capacity. Excitation prior to slaughter caused lower live weight, higher meat water holding capacity, lower shear value higher yield and lower lightness (L) and higher redness (a) values than non-excited and anesthetized controls. Papa and Fletcher (1988) evaluated the use of antemortem wing restraint on subsequent muscle shortening and breast meat toughness. Wing restraints applied just prior to slaugh­ter, with no stunning, did not result in any significant effect on breast meat tenderness. McGinnis et al. (1989a) found that sodium pentobarbital can delay early rigor processes but that following 24 h aging no effects were noted on breast meat tenderness. In a later study, McGinnis et al. (1989b) reported that sodium pentobarbital and surgical denervation of pectoralis major alters the profile of early rigor development.

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Environmental conditions

Simpson and Goodwin (1975) reported that tenderness of broilers was significantly influ­enced by plant source and by season of the year in which Fall produced the most tender meat and Summer the least tender. Froning et al. (1978) evaluated cold and hot tempera­ture stress, sodium pentobarbital and free struggle on frozen turkey pH, water holding capacity, shear thaw loss and color. They reported that free struggle and heat stress re­sulted in significantly darker, more red, higher pH (free struggle only) and higher shear force. Babji et al. (1982b) reported that heat stress resulted in significantly lower raw muscle pH, cooked meat pH, water holding capacity, myoglobin concentration, total pig­ment concentration, redness (a) and higher lightness (L) and yellowness (b) values while cold stress resulted in significantly lower shear values. In a study on the effect of temperature on postmortem glycolysis of poultry meat, Kahn (1971) used two antemortem treatments to produce birds with high post-slaughter pH and low post-slaughter pH. The high post-slaughter pH treatment (pH 6.7-7.0) were produced by using well rested birds slaughtered in restraining cones to minimize voluntary and involuntary struggling. The low post-slaughter pH treatment (ph 6.1-6.3) were produced by allowing the birds to struggle freely during slaughter while hanging by the legs. Lee et al. (1976) evaluated the effect of heat stress (38 C), cold stress (4 C) and extreme cold stress (-20 C) for 6 h prior to slaughter on subsequent muscle glycogen, pH, and moisture content, cooked meat shear and serum lactate dehydrogenase and creatine Phos­phokinase. Results showed that heat stress resulted in significantly greater shear values, lower 24 h pH, and lower 24 h raw muscle moisture. Wood and Richards (1975b) evaluated actual specific and non-specific stress conditions on postmortem muscle reactions. Non-specific stress was defined by commercially obtained birds from a slaughter plant and compared to laboratory reared birds. The only significant effect was for the stressed birds to develop maximum tension in a longer postmortem time than the control birds. Free struggle, cold stress and heat stress was also evaluated. Heat stress and heat stress with free struggle resulted in significantly greater tension develop­ment and heat stress plus free struggle resulted in significantly lower 0 time pH. Shear value was not affected. Cold stress at 2 C for 2 h resulted in significantly lower time to reach maximum tension and a significantly greater shear value.

Physiological stress

Many of the above factors (feed and water deprivation, struggling, stunning, metabolic drugs, and temperature) have often been referred to as antemortem "stress" factors. The resistance of animals to "stress" is tremendously variable and explains why similar preslaughter conditions can lead to both dark, firm and dry (DFD) meat in beef and pale, soft and exudative (PSE) meat in pork. Stress can best be viewed as being a physiological response to, or a perception of, some environmental input. Thus, individuals often per­ceive and react differently to a particular input. Many of the contradictons listed above may be due to differences in the response to the stressors used.

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The reactions that occur in muscle upon death are relatively constant. The rate and degree to which the muscles undergo rigor mortis are in part affected by antemortem conditions. These conditions can be mediated by a physiological response to stress, as in extreme cases with PSE pork in which populations of pigs are know to be stress susceptible. Simi­lar conditions in poultry have been suspected but have yet to be firmly established. For example, problems such as pale exudative turkey breasts, variation in broiler breast meat color, and variations in breast meat tenderness have all been suspected as being due to a stress response in the bird. The previous work using various anesthesia and free struggle during slaughter allude to this point. It would be advantageous to be able to partition those factors that actually result in a mea­surable physiological response to stress. The negative effect of pork stress syndrome (PSS) on the production of pale, soft and exudative (PSE) meat is well established. In this instance, the stress response (antemortem) in the animal greatly affects the postmortem reactions which affect meat quality. An example of this can be found in the reports of dark turkey meat as a function of preslaughter conditions. Froning et al. (1978) reported that heat stress and free struggle during slaughter resulted in significantly darker and more red raw turkey breast meat than cold stress or sodium pentobarbital treated birds. The authors stated that this occurrence was not similar to PSE conditions found in pork since the heat stress and free struggle also resulted in lower muscle pH values. Babji et al. (1982), in contradiction to the previous article by Froning, reported that turkeys subjected to heat stress resulted in significantly lighter breast meat. This was partially explained by the difference with the lighter meat having a significantly lower pH. Compared to the control and cold stressed birds, the heat stressed meat had less hemoglobin than the control, less myoglobin that either the control or the cold stressed birds, and less total pigment than either. Ngoka et al. (1982) reported that struggle during slaughter and antemortem excitement resulted in darker and more red breast meat. This difference could not be explained by pH or hemoglobin content in the muscle. The free struggle and excited treatment did have a significantly greater myoglobin and total pigment content. In a subsequent paper, Ngoka and Froning (1982) hypothesized that the darker breast color could have been due to cytochrome C content in the muscle.

In a recent study (Fletcher et al., 1991), high levels of epinephrine injections in broilers 0-24 h prior to slaughter resulted in a high proportion of birds with very dark breast meat. No relationship between color and muscle pH was observed. A comparison between breast meat lightness values (L*) with myoglobin (Mb) and hemoglobin (Hb) concentrations resulted in a significantly negative relationship for Hb and none for Mb. Newell and Shaffner (1950) used epinephrine in an attempt to increase blood loss during killing. The hypothesis being that epinephrine, known to cause a sharp increase in blood pressure by strengthening the heart contraction and by decreasing peripheral blood flow, would result in greater blood loss following killing. Results indicated just the opposite with increased epinephrine levels being associated with decreased blood loss. These results indicate that variations in breast meat color are not likely due to variation in muscle pH, rate of postmortem glycolysis or the effects of stress on these factors. The results of Froning et al. (1978), Ngoka et al. (1982), Babji et al. (1982), Ngoka and Froning (1982) and Fletcher et al. (1991) indicate that stress may have an independent effect on the vascular nature of the muscle and subsequent heme pigment concentration. There still exists some question regarding the nature of the heme and the relationship of the stress reaction on meat quality.

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Conclusion

Numerous antemortem factors have been shown to affect meat quality. Most of the short term factors have been associated with modifying the biochemical reactions during post­mortem glycolysis. Evidence exists that meat quality factors may also be independently influenced by stress responses affecting the hypothalamic-pituitary-adrenal complex. Vari­ations in breast meat color may be less a function of final muscle pH and more a function of stress responses on the vasodilation of muscle capillaries.

References

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Babji, A. S., G. W. Froning and D. A. Ngoka, 1982b. The effect of preslaughter envi­ronmental temperature in the presence of electrolyte treatment on turkey meat quality. Poultry Sei. 61:2385-2389.

deFremery, D., 1965. The effect of anesthesia during slaughter on some biochemical properties of chicken breast muscle. Poultry Sei. 44:1370.

deFremery, D. and M. F. Pool, 1960. Biochemistry of chicken muscle as related to rigor mortis and tenderization. Food Research 25:73-87.

deFremery, D., M. F. Pool and H. Lineweaver, 1962. Poultry tenderness and post-mor­tem glycolysis. Proc. 12th Worlds Poultry Cong, pp 418-421.

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Fletcher, D. L., T. G. Uijttenboogaart and F. J. G. Schreurs, 1991. Unpublished data. Froning, G. W., A. S. Babji and F. B. Mather, 1978. The effect of preslaughter temper­

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Goodwin, T. L., W. C. Mickelberry and W. J. Stadelman, 1961. The influence of hu­mane slaughter on the tenderness of turkey meat. Poultry Sei. 40:921-924.

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Klose, A. A., B. J. Luyet and L. J. Menz, 1970. Effect of contraction on tenderness of poultry muscle cooked in the prerigor state. J. Food Sei. 35:577-581.

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Landes, D. R., L. E. Dawson and J. F. Price, 1971. Protein extractability of turkey breast muscle exhibiting different rates of post-mortem glycolysis. J. Food Sei. 36:122-124.

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Ngoka, D. A., G. W. Froning, S. R. Lowry and A. S. Babji, 1982. Effects of sex, age, preslaughter factors, and holding conditions on the quality characteristics and chemical composition of turkey breast muscles. Poultry Sei. 61:1996-2003.

Papa, C. M. and D. L. Fletcher, 1988. Effect of wing restraint on postmortem muscle shortening and the textural quality of broiler breast meat. Poultry Sei. 67:275-279.

Riley, P. K., D. M. Janky, R. H. Harms and J. L. Fry, 1976. The effect of dietary potassium chloride on broiler yields. Poultry Sei. 55:1505-1507.

Shrimpton, D. H., 1960. Some causes of toughness in broilers (young roasting chickens). I. Packing station procedure, its influence on the chemical changes associated with rigor mortis and on the tenderness of the flesh. Brit. Poultry Sei. 1:101-109.

Simpson, M. D. and T. L. Goodwin, 1975. Tenderness of broilers as affected by pro­cessing plants and seasons of the year. Poultry Sei. 54:275-279.

Stadelman, W. J. and R. G. Wise, 1961. Tenderness of poultry meat. I. Effect of anes­thesia, cooking, and irradiation. Food Technol. 15:292-294.

Wood, D. F. and J. F. Richards, 1975. Effect of pre-slaughter epinephrine injection on postmortem aspects of chicken broiler pectoralis muscle. Poultry Sei. 54:520-527.

Wood, D. F. and J. F. Richards, 1975. Effect of some antemortem stressors on postmor­tem aspects of chicken broiler pectoralis muscle. Poultry Sei. 54:528-531.

18

Table 1 Summary of poultry carcass (C) and meat (M) defects and their suspected area of orgin during production.

Defect - carcass (C) or meat

Bloody thigh Breast blisters Brown spots (melanin) Bruises Composition Conformation Fat stability Feather color Focal myopathy Hemorrhages Leg problems Meat color Meat staining Meat tenderness Muscular dystrophy Oily bird syndrome (OBS) Off flavors Scabby hip Skin color Yield

(M)

C,M C C C,M C,M C M C M C,M C M M M M C M C C,M C,M

Cause

management management genetics management, nutrition genetics, nutrition genetics, nutrition nutrition genetics genetics nutrition, management, nutrition genetics, management management, nutrition genetics, management genetics management, nutrition management, nutrition nutrition genetics, management, nutrition genetics, management, nutrition

19

20

POST MORTEM PROCESSING FACTORS AND POULTRY MEAT QUALITY

T.G. Uijttenboogaart

Spelderholt Center for Poultry Research and Information Services, Agricultural Research Service (DLO), 7361 DA Beekbergen, The Netherlands

Abstract

Effects of processing on a number of poultry meat quality parameters are reviewed. Most research has been conducted on the tenderness/shear force of poultry (breast) meat in relation to hot boning, electrical stimulation, etc. Functional properties like emulsifying or waterbinding properties and the pH mainly depend on the state of the rigor processes in the muscles. These processes can be delayed by chilling or accelerated by electro-stimulation. In pre-rigor meat, functional quality properties can be affected by post-mortem slaughtering and chilling processes. The final functional properties of post rigor meat mainly depend on ante-mortem processing factors.

Introduction

The quality of poultry meat is influenced by both ante- and post-mortem process factors. The extent to which the quality of the obtained poultry meat is influenced by the different processing factors is not always clear. The ante-mortem processing factors like catching, handling and transport, temperatures, starvation, etc. are important and their effects on meat quality have been summarized by Fletcher (1991). This contribution will deal with the post-mortem processing factors as they affect the most important quality characteristics of poultry meat. These most important characteristics, the processing factors and the effects on meat quality characteristics are given in Table 1.

21

Shear force / tenderness / sarcomere length

The effect of stunning on the tenderness of poultry meat is not clear. Thomson et al., (1986) in 1 out of 2 experiments showed a significant stun effect on Warner Bratzler shear force. The stunned birds showed lower shear force values than the non-stunned birds. The effects of stunning could partly be caused by the absence of free struggle of the stunned birds and not only by the muscle contraction during the stunning treatment. Post-mortem aging effect in this study however had a much more pronounced effect on tenderness/shear force. Mohan Raj et al. (1990) showed significant differences comparing electrical and gaseous stunning on texture of broiler M. pectoralis major. Volodkevitch texture values were 2.19 kg for the electrically stunned group, and 2.02 kg for the C02 stunned group. In this study there was no non-stunned control group.

Hot boning has a very negative effect on broiler or turkey breast meat tenderness. This was shown in many studies (Stewart et al., 1984, Lyon et al., 1985, Sams and Janky, 1986, Thomson et al., 1986, Dawson et al., 1987, Froning and Uijttenboogaart, 1988, Kim et al., 1988, Uijttenboogaart and Reimert, 1988, Bilgili et al., 1989, Wakefield et al., 1989,). The increased toughness coincides with contraction of the muscle and a shorter sarcomere length. (Kim et al., 1988, Papa and Lyon, 1989, Wakefield et al., 1989). The increased toughness is very likely caused by super contraction of the muscle fibers. The contraction can take place due to the large amount of energy present in the pre-rigor muscle. The cold boned muscles are during passage of the rigor mortis still fixed to the bones and thus can not contract in the same rate. Papa and Lyon (1989) show a difference in texture at different locations within the muscle. This difference seemed consistent with variations of contraction within the muscle.

Wakefield et al. (1989) also show some effects of the rate of rigor onset, the rate of cooling and the chilled storage time oOn tenderness. Especially when turkey meat with pH20 > 6.4 was chilled by immersion chilling to 7°C within 65 minutes post mortem and subsequent chilling in ice water toughness was induced. Chicken meat showed the same effects, when freezing started within 2 hours post mortem. This effect is quite similar to the cold shortening effect as described by Locker and Hagyard (1963) in beef muscle. Chilling of pre-rigor beef to temperatures below 10°C shows a remarkable increase in toughness of the meat. The effect described by Wakefield et al. (1989) disappeared after 7 days of chilled storage. Uijttenboogaart and Reimert (1988) showed a much smaller effect of cutting of legs, thighs and drumsticks from broiler chickens on the shear force of the leg muscles. Probably these muscles are not able to contract that much, to induce the same effect as in the breast muscle.

22

Electrical stimulation (ES) has a toughening effect on shear force values of cold boned broiler breast meat, deboned directly or 25 minutes after evisceration. (Froning and Uijttenboogaart, 1988). In the same study a slight tenderizing effect has been found, when deboning of the breast meat was carried out 2 and 4 hours after evisceration.

Webb et al. (1988) describe a Minimum Time Process (MTP), in which a combined electro-stimulation and conditioning process before scalding and picking, leads to tender breast meat after hot boning. An effect of a delayed picking operation or an aging step pre-scalding on breast meat tenderness was not found by Uijttenboogaart and Fletcher (1989). When MTP is compared to normal hot boned breast meat, shear force values did not show a beneficial effect of the MTP (Uijttenboogaart and Fletcher, 1991). Wakefield et al. (1989) also showed no effect of electro-stimulation of turkeys on meat tenderness. Electro-stimulation of chickens caused an overall toughening due to the increased rigor shortening in carcasses with pH20 < 5.8 Thompson et al. (1987) showed a significant decrease in toughness of hot boned breast meat using low voltage electrical stimulation. High voltage ES had no effect on toughness. This effect was reversed when stimulating cold boned carcasses. Then the high voltage ES resulted in a decreased acceptable toughness. Tenderness response (shear force) was more highly related to myofibrillar disruption and increased sarcomere length than to pH and ATP breakdown.

Papa et al. (1989) tried to influence shear force values of M. pectoralis major by restraining the wings. They found longer sarcomeres and a slight but significant decrease in shear force values when deboned 2 and 3 hours post mortem.

Sams and Janky (1986) found an effect of brine chilling of hot boned broiler breast meat on tenderness (shear force). The shear forces found when shearing this meat were of the same level as the shear force values of the breast meat deboned after chilling (chill boned) but still much higher than the samples deboned 24 hours post mortem (age boned). They suggest that tissue chloride concentration may be the reason for this lower shear force.

The effect of storage on tenderness is not very clear. Griffiths et al. (1984) found no significant difference in turkey breast muscle during cold storage. Grey et al. (1986) however monitored a slightly increase of toughness in turkeys during cold storage at 4°C. This does not fit into the theory of protein breakdown during cold storage and subsequent decreasing toughness (Penny, 1980, Kopec et al., 1985, Ouali, 1990).

23

Color

The effect of processing factors on meat color has not been studied very extensively. Differences in meat color very often are related to feed differences or ante-mortem factors like stress, handling, etc. In pig processing color differences in meat are described very often. The occurrence of PSE (Pale, Soft and Exudative) or DFD (Dark, Firm and Dry) meat is quite common. These qualifications are not that common in poultry meat processing but complaints about variation in color and terms like PSE are increasingly heard. Froning and Uijttenboogaart, (1988) found an effect of electro-stimulation on breast meat color. Post-mortem electro-stimulation significantly increased a* (CIE-Hunter redness values) and decreased L* (CIE-Hunter lightness) values. This means that the electro-stimulated meat was more red and darker than the not stimulated controls. Mohan Raj et al. (1990) found very small but significant differences in L* and a* values of meat from broilers stunned electrically and with gas (C02 and argon). Conditions during chilled storage of meat largely influence meat color (Faustman and Cassens, 1990). Especially the oxidative stability of myoglobin is very important. Several factors like pH of the meat, light, temperature or wrapping material affect meat color. Color stability in poultry meat has not been subject of many studies. Reason may be the lower myoglobin content of poultry (breast) meat compared with for instance beef and therefore the smaller effects of storage on discoloration of the meat.

Taste

Griffiths et al. (1984) and Grey et al. (1986) showed some slight effects of evisceration on the development of meat flavor. Storage of uneviscerated turkeys at 4°C during 10 days and subsequent storage at -2°C resulted in a slight but significant change in flavor. The gut flora might be responsible for the development of a "strong" or "gamey" flavor in breast meat.

pH

Post-mortem treatments of poultry affect the rate of pH change in meat, but not the post-rigor pH value measured 24 hours post-mortem. Processes that affect the rate of the rigor change also affect pH changes in the meat. Lyon et al. (1985) found a significant effect of hot boning on pH 1 hour post mortem. After 4 hours post mortem the pH difference with the other groups had disappeared. This pH effect however might be a temperature effect.

24

By taking off the meat from the carcass the temperature decreases faster than in the meat from the cold boned groups. The rigor processes in the muscle are slowed down by the low temperature resulting in a higher 1 hour post mortem pH.

Murphy (1986) and Murphy et al. (1988) found no effects of stunning turkeys compared with non stunned birds at times later than 4 hours post mortem. Only directly after the stunning operation a higher pH and ATP content in the muscle were observed. Stunning has a delaying effect on the onset of rigor. This was demonstrated by the results of glycogen, pH, ATP, R-value and extractable protein examinations. Veerkamp et al. (1987) compared low and high current during electric stunning on muscle pH 20 minutes post mortem. The birds stunned at the highest current showed a significant higher pH. Thomson et al. (1986) and Kim et al. (1988) also observed a higher muscle pH in stunned chicken broilers 20 minutes to 1 hour post mortem. After that time this difference disappeared. These results agree with the findings of Murphy (1986). Mohan et al. (1990) also found a very significant effect of stunning method (electrical versus gaseous) on pH 20 min post mortem. A significant, but smaller, difference still exists after 24 hours.

Emulsifying properties

In general emulsifying properties mainly are affected by further processing treatments of poultry meat or the composition (fat/water and fat/protein ratio) of the meat. Processing treatments during slaughter, evisceration and washing/chilling do not affect the emulsifying properties of the meat to a large extent. Murphy (1986) and Murphy et al. (1988) did not find any differences in emulsifying properties of turkey when sampled at times 0, 4, 8 and 24 hours post mortem. Also stunning did not affect the functional properties as expressed by the emulsion stability evaluations. Kim et al. (1988) found better emulsifying capacity when broiler chickens had been stunned. Hot boning caused a significant decrease of the emulsifying capacity.

Water holding capacity / cooking loss

Weise et al. (1982) showed no differences in water holding properties due to heart fibrillation during the electrical stunning operation. Schneider et al. (1984) found significant differences in grill losses of ducks and geese due to stunning voltage. For ducks the grill losses increased with increasing voltage and for geese the opposite effect was observed. No significant differences have been found with broilers.

25

Thomson et al. (1986) showed a significant "stun x age" interaction for weight loss after cooking. The losses were found to be higher at 24 hours post mortem compared to 20 minutes post mortem. This might be an effect of the muscle pH and the differences that are found due to the water binding properties of the muscle proteins. From their results the effect of stunning however is not very clear. Kim et al. (1988) found no significant differences in expressible moisture and cooking losses in stunned and non-stunned birds. Mohan Raj et al. (1990) showed no significant effect of stunning method (electrical versus gaseous) on cooking loss.

Electro-stimulation increases cooking losses and expressible moisture (Froning and Uijttenboogaart, 1988). This may be due to the fact that electro-stimulation has a large effect on muscle pH. By changing the pH the water binding properties of the proteins are very much influenced. The pH values drop close to the iso electric point (IEP) of most of the proteins. Near the IEP in general the water binding / holding capacity of proteins is minimal. This was also shown by Bouton et al. (1972) in ovine muscles.

Blood spots / red wing tips

The occurrence of blood spots and red wing tips mainly is caused by the stunning operation. Veerkamp et al. (1987) observed a highly significant effect of the current (50 A and 100 A) during electric stunning on the occurrence of hemorrhages in the breast meat. A high amperage caused a higher incidence of hemorrhages. Wabeck (1988) showed that 50 - 80 V (AC) provided a maximum bleed out (45%) when compared to no stun (32.5%). At higher voltages the bleed out levels drop to the no stun level. This result is in agreement with the findings of Veerkamp and De Vries (1983). They found a maximum bleed out (about 35%) at 75 V when compared with higher voltages (33 to 28% at 100 V to respectively 200 V). According to Wabeck (1988) the frequency of the stunner is also very important. At a frequency of the current of 120 Hz a maximum bleed out has been found. Especially at the higher frequencies there is a considerable muscle contraction which can result in darkened areas in the muscles. The problems with red wing tips are also related to the stunning, bleeding and picking operation. The condition of engorged blood vessels in the wing is specially noticeable in the area where the wing joins the body. Rupture of the vessels can cause a bruise-type area. During the picking procedure the picking fingers move the blood progressively down to the wing tip. Cold weather conditions intensify this problem. Veerkamp and De Vries (1983) report panel data that show a highly significant effect of the voltage used during the stunning operation. The group stunned at 75 V has a much lower incidence of red wing tips than those stunned at 200 V.

26

References

Bilgili, S.F., W.R. Egbert and D.L. Huffman, 1989. Research note: effect of postmortem aging temperature on sarcomere length and tenderness of broiler pectoralis major. Poultry Science 68(11): 1588-1591

Bouton, P.E., P.V. Harris and W.R. Shorthose, (1972). The effects of ultimate pH on ovine muscle: water holding capacity. J. Food Sei. 37:351-355

Dawson, P.L., D.M. Janky, M.G. Dukes, L.D. Thompson and S.A. Woodward, 1987. Effect of post-mortem boning time during simulated commercial processing on the tenderness of broiler breast meat. Poultry Science 66 (8): 1331-1333

Faustman, C. and R.G. Cassens, 1990. The biochemical basis for discoloration in fresh meat: a review. J. of Muscle Foods 1:217

Fletcher, D.L., 1991. Ante mortem factors related to meat quality. Proceedings of the 10th Symposium on the Quality of Poultry Meat, Doorwerth, The Netherlands

Fletcher, D.L. and CM. Papa, 1988. Effect of aging temperature on broiler breast meat. Poultry Science 67(8): 1147-1153

Froning, G.W. and T.G. Uijttenboogaart, 1988. Effect of post-mortem electrical stimulation on color, texture, pH, and cooking losses of hot and cold deboned chicken broiler breast meat. Poultry Science 67:1536

Grey, T.C., G.C. Mead, N.M. Griffiths and J.M. Jones, 1986. Effects of evisceration and storage temperature on changes in meat quality of traditional farm-fresh turkeys. British Poultry Science 27(3):463-470

Griffiths, N.M., G.C. Mead, J.M. Jones and T.C. Grey, 1984. Effect of storage on meat quality in uneviscerated turkeys held at 4 degrees C. British Poultry Science 25 (2):259-266

Jones, J.M., 1988. Poultry—the versatile food. Developments in food proteins. 6:35-71 Barking Elsevier Applied Science Publishers

Kim, J.W., D.L. Fletcher and D.R. Campion, 1988. Research note: effect of electrical stunning and hot boning on broiler breast meat characteristics. Poultry Science 67 (4): 674-676

Kopec, W., T. Smolinska and T. Trziszka, 1985. Postmortem meatbolism and ultrastructural changes in frozen duck tissue: Proteolytic changes. Arch. Gefliigelk. 49,5:168

Locker, R.H. and C.J. Hagyard, 1963. Cold shortening effect in beef muscle. J. Sei. Food Agric. 14:787

Lyon, CE. , D. Hamm and J.E. Thomson, 1985. pH and tenderness of broiler breast meat deboned various times after chilling. Poultry Science 64 (2)

Mohan Raj, A.B., T.C. Grey, A.R. Audsely and N.D. Gregory, 1990. Effect of electrical and gaseous stunning on the carcase and meat quality of broilers. British Poultry Science 31:725

Murphy, B.D., 1986. Effect of antemortem electrical stunning on avian muscle. Dissertation Abstracts International, B; 46(9):2889

27

Murphy, B.D., R.J. Hasiak and J.G. Sebranek, 1988. Effect of antemortem electrical stunning on functional properties of turkey muscle. Poultry Science 67(7): 1062-1068

Ouali, A., 1990. Meat tenderization: Possible causes and mechanisms. A review. J. of Muscle Foods 1:129

Papa, CM. and CE . Lyon, 1989. Shortening of the pectoralis muscle and meat tenderness of broiler chickens. Poultry Science 68(5):663-669

Papa, CM., CE. Lyon, and D.L. Fletcher, 1989. Effects of post-mortem wing restraint on the development of rigor and tenderness of broiler breast meat. Poultry Science 68:238-243

Penney, I.F., 1980. The enzymology of conditioning. In: Developments in meat science. Vol 1. Ed.: R. Lawrie. Elsevier Appl. Sei., London.

Sams, A.R. and D.M. Janky, 1986. The influence of brine chilling on tenderness of hot-boned, chill-boned, and age-boned broiler breastfillets. Poultry Science 65 (7): 1316-1321

Schneider, K.H., P. Dzialek and H. Pingel, 1984. Einfluss der Betäubungsspannung auf die Schlachtkörper- und Fleischbeschaffenheit des Geflügels. Fleisch 38 (5):94-96

Stewart, M.K., D.L. Fletcher, D.L. Hamm and J.E. Thomson, 1984. The influence of hot boning broiler breast muscle on pH decline and toughening. Poultry Science 63:1935.

Thompson, L.D., D.M. Janky and S.A. Woodward, 1987. Tenderness and physical characteristics of broiler breast fillets harvested at various times from post-mortem electrically stimulated carcasses. Poultry Science 66:1158-1167

Thomson, J.E., CE . Lyon, D. Hamm, J.A. Dickens, D.L. Fletcher and A.D. Shackelford, 1986. Effects of electrical stunning and hot deboning on broiler breast meat quality. Poultry Science 65 (9): 1715-1719

Uijttenboogaart, T.G. and D.L. Fletcher, 1989. The effects of delayed picking and high temperature conditioning on the texture of hot- and cold-boned broiler breast meat. J. Muscle Foods 1:37-44

Uijttenboogaart, T.G. and D.L. Fletcher, 1991. Data to be published. Uijttenboogaart, T.G. and H.G.M. Reimert, 1987. Warm ontbenen van slachtkuikens.

Gevolgen voor de malsheid. Vleesdistributie en Vlees technologie 22,7:34 Veerkamp, C.H., A.H.H. Rincker, CPieterse and A.W. de Vries, 1987. Onderzoek naar

de verdovingskondities op de kwaliteit van slachtkuikens. Spelderholt report 469. Beekbergen, The Netherlands.

Veerkamp, C.H. and A.W. de Vries, 1983. Influence of electrical stunning on quality aspects of broilers. In: Stunning of animals for slaughter, G. Eikelenboom, editor. Martinus Nijhoff Publishers. The Hague, The Netherlands.

Wabeck, C , 1987. How stunning affects product quality. Turkey World 63(4):34, 36-38 Wabeck, C , 1988. How stunning affects product quality. Poultry International 27 (2):48,

50-52

28

Wakefield, D.K., E. Dransfield, Down, N.F. and A.A. Taylor, 1989. Influence of post-mortem treatments on turkey and chicken meat texture. International journal of food science and technology 24(l):81-92

Webb, J.E., R.L. Dake and R.H. Forsythe, 1988. Electrical stimulation and conditioning in the minimum-time process (MTP) for tender non-aged poultry. Proc. XVIII World's Poultry Congress, Nagoya, Japan :1350

Weise, E., I. Schutt and R. Levetzow, 1982. Auswirkungen einer Tierschutzgerechten elektrischen Betäubung auf die Fleischqualität geschlachteten Geflügels. Berliner und Münchener Tierärztliche Wochenschrift 95 (13):241-247

29

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30

STUNNING AND MEAT QUALITY

S. Lindholst

Lindholst & Co AIS, Vestermollevej 9, DK-8380, Trige, Denmark

Abstract

Optimization of stunning methods in relation to meat quality are briefly discussed. Gas stunning improves meat quality although it is more expensive than electrical stunning.

The meat quality is to a very high degree influenced by the events immediately before and during the slaughtering. This is not a new acknowledgement and surely one of the reasons why there are so many religious rules prescribing the sequence of events of the slaughtering process. These rules may originate from practical - but at that time incomprehensible - experiences as to the methods ensuring good meat quality.

Many religious rules emphasize the importance of well-being and good treatment of the animals before and during the slaughtering. New reports have proved that the stress situation of the slaughtered animals can be identified by means of pH measurements long time after the slaughtering. The best meat quality is obtained by calm animals whereas exhausted animals (high pH value) and excited animals (low pH value) generally give lower meat quality.

Realizing this fact the poultry industry has invested large amounts in methods which reduce the stressing conditions in connection with catching, transportation and suspension of the birds. On the other hand methods of stunning and slaughtering have not been changed substantially - at least not in Europe.

Electrically stunning of poultry is the most commonly used method in Europe. It is efficient and cheap and does not make great demands on the subsequent slaughtering. The latest development in electrical stunning has optimized the electrical signal as to voltage, amperage, design and frequency. Although this development has improved the method of electrical stunning considerably, the method causes reduction of the meat quality in the form of insufficient bleeding, blood spots especially in the breast meat, stressed breast meat, etc.

31

Realizing the limitations as to quality of the method of electrical stunning, the company, which I represent, in 1982 started to develop alternative methods. From the slaughtering of other types of animals and from extensive literature about the subject, we knew the advantages but also the technical problems of gas stunning. In 1985 we finished the development of an on-line gas stunner for poultry which we have since been selling on the Japanese market.

The experience with gas stunning shows that poultry meat obtains a better meat structure and colour and has a longer "shelf life". This experience is also well-known in connection with gas stunning of other species.

Gas stunning influences the central nervous system and does not paralyse the musculature, especially not the heart musculature. Consequently, the bleeding is much better and the bleeding time shorter than by electrical stunning. Effusion of blood, especially in the breast meat, is very seldom.

Visually, gas stunning seems to be a gentle method by which the birds seem to hang relaxed before slaughtering. Gas stunning makes heavy demands on both the stunning equipment and on the method of killing and is more expensive than electrical stunning. This may be the reason why the method is not so commonly used in Europe although it results in meat of a definite better quality.

The relation between stunning and meat quality is that an optimal method of stunning is a condition for obtaining good meat quality. This connection has been known and accepted for a long time. However, the effect of a bad stunning on the meat quality has first been fully realized in connections where the meat is used for further processing. Thus the latest development within the industry for processed products will naturally result in an increased interest for optimizing stunning and slaughtering methods.

32

OCCURRENCE AND JUDGMENT OF CHARACTERISTICS IN POULTRY MEAT INSPECTION

R. Fries

Institute of Food and Meat Hygiene and Technology, 3000 Hannover, School of Veterinary Medicine, Germany

Abstract

For surveillance of poultry flocks in the slaughterhouse the parameters in use shall be qualitatively and quantitatively well defined from the beginning. Some unspecified attributes, worth being counted, are also described. Judgment and applicability for surveillance of the flocks in the slaughterhouse are discussed.

Introduction

In Germany the processing of poultry has been highly mechanized; the evisceration lines work with up to 7,200 birds/ h. The rate of condemnation in 1989 amounted to 1.18 % (4). Nevertheless, important affections counted in a slaughterhouse in NW-Germany, occurred in carcasses both, fit and unfit for consumption.

Important Attributes (*) in Broiler Flocks 1985, 1987 and 1989 in Percent (data from 1, 2,3).

1985 1987 1989a 1989b

Range

Approved for human consumption (random samples)

0.11-1.11 0.33-4.44 0.75-1.58 0.25-1.75

0.11-4.44

Condemned (total count)

12.0-28.8 20.5-33.3 29.0-47.7 25.2-37.8

12.0-47.7

Flocks examined (**\

8 8 3 3

22

Birds examined approved

7.200 7.200 3.600 2.396

20.396

cond'd

2.484 2.952

814 374

6.624

* Important attributes: discolourations, total ruptures, tumors, deep dermatitis, necrosis, perihepatitis, pericarditis.

** The flocks ranged between 16,000 and 42,000 birds.

33

* Overlooking of unfit carcasses due to excessive work demand (environment of the inspection place, speed of the line or hygienic or health state of the flock).

* judgment depends on the opinion of the individual inspector.

Collecting data on attributes in a flock can lead to knowledge of the reason for damage. The different affections can be attributed to specific parts of the meat production chain:

Reasons for Macroscopic Affections in the End Product

Factors Affections (e.g.)

fattening period * diseases or pathogenic

microorganisms * environmental factors

underweight birds, inflammation of skin and cavity, reduced shelf-life, increased mortality rate

transportation including * catching * loading * transporting * unloading * hanging on the shackles

fractures, lesions, haemorrhages, death during transport

slaughtering and processing, meat inspection

incomplete evisceration, overlooking of damage, mechanical damage, contamination

end product improper handling

reduced shelf-life

Aspects to be considered when setting up a surveillance system:

A surveillance system additional to the existing inspection of live birds and slaughtered carcasses would enable both the producer and the inspector to obtain more information than is possible at present. However, some technical questions arise: * attributes to be looked for. Common attributes which lead to the condemnation of carcasses are laid down in Directive 71/118/EEC. * grading of affections: If data on attributes in the slaughterhouse are collected, it is necessary to consider their intensity, spread and location.

34

Exact limits of dimensions of the attributes mentioned above have not yet been established. This is nevertheless the condition for estimation and counting of affections. On the other hand, several affections of minor importance can occur in a single carcass, the sum total leading to the whole carcass being condemned. In circumstances such as this quantitative limits cannot be given. * knowledge of the frequency of occurrence is a condition for evaluation of the results of surveillance.

Presentation:

1. Inflammation of Bursa Sternalis ("Breast Blisters")

Pathological-anatomical : * localized swelling of skin and bursa; inflammation of bursa without affection of the skin

may be possible * different grades (swellings, discolourations, suggillations, necroses).

Occurrence of Bursitis Sternalis in Broiler Flocks:

1985

1987

1989 a 1989 b

approved

41.0 % (n=7200)

27.6 % (n=7200)

72.8 % * 27.2 % * *

6.8-7.9 (n=3600) 0 -0.9 (n=2396)

condemned

14.0 % (n=2280)

19.0 % (n=2952)

57.9 % * 42.1 % * *

5.0-10.9 % (n= 814) 0 -6.1 % (n= 374)

attributes counted

*

*

* * *

* * *

Judgment of the affection depends on the grade: * slightly swellings, little spread : no consequence ** swellings, suggillation of surroundings : part to be condemned *** swellings, suggillations and : look for other injuries

heavy discolourations

Task of surveillance: feedback for quality of housing systems Count as a lower limit for surveillance: position (**).

35

2. Deep Dermatitis

Pathological-anatomical : * Swellings and thickening of skin, yellow-brownish and sparkling fat * subcutis: oedema up to fibrins and necroses more extended under the skin than on the

surface * injured muscles (petechia) depending on intensity * relations to inflammation of organs cannot be excluded * localized on thighs, abdomen, cloaca area.

Deep Dermatitis in Broiler Flocks:

approved condemned

1985 0.1% (n = 7200) 1987 0.3 % (n = 7200) 1989 a 0.1 -0.2 % (n = 3600) 1989 b 0 -0.1 % (n = 2395)

5.2% (n = 2484) 17.8 % (n = 2952)

7 .1-25.6% (n = 814) 0.7 - 7.9 % (n = 374)

Judgment: carcasses with the affection have to be excluded from human consumption generally.

Applicability for surveillance: on account of the exclusive character of the attribute it can be used as a morphological parameter in surveillance of the meat inspection and as a means of obtaining further information on this disease.

3. Scabby Skin I Scabby Hip

Pathological-anatomical : * Brownish eczema on the surfaces like honeycombs due to feather-follicles, redeemable * in severe cases darkened and firm skin * surroundings and subcutis normally unchanged * localization: thighs, hip, back.

Occurrence of Scabby Skin in Broiler Flocks (data from 1987):

counted in percent of birds examined

in percent of affections localized extended

approved

condemned

61.9 %

59.5 %

46.7 %

37.4 %

53.3 %

62.6 %

36

Jugement: * 1 attribute, localized, < 3 cm diameter * > 3cm diameter (extended) * severe local affection or

several smaller injuries

: no consequence : part to be condemned

: bird to be condemned

Applicability for surveillance: Data show that scabby skin is not estimated as a cause for condemnation of the whole bird or localized parts, which may be on account of its frequent occurrence. Data show also that extended affections are seen more often in the birds condemned. So the occurrence of this attribute in the total number of condemned and approved carcasses could be an aid to assessment of occurrence in the flock and for suitable instructions for the meat inspectors.

4. Inflammation of Organs and/or Cavity

Pathological-anatomical: * dullness of seröses up to fibrin layers * liver: hypertrophy and swellings, necroses, perihepatitis * spleen: necroses * pericarditis * cavity and air sacs: accumulation of fluids up to solid masses.

Inflammation of Localizations in the Cavity (Broilers):

pericarditis pen-hepatitis(*)

inflammation of cavity

1985

1987

1989

a)

1989 b)

approved condemned

approved condemned

approved condemned

approved condemned

0.1 % 1.7 %

0.6 % 0.7 %

0.1 - 0.7 % 0.0- 1.2 %

0.0 - 0.3 % -

0.1 % 2.2 %

-1.1 %

0.2 - 0.4 % 7.3 - 16.8 %

0.1 - 0.6 % 7.5 - 12.7 %

< 0.1 % 1.1 %

0.1 % 0.7 %

not examined H

H

It

*) in 1989 attributes tested as "inflammation of the liver"

37

Judgment: Condemnation of the slaughtered bird, if one of the localizations mentioned above is affected. Explanation: bacteraemia cannot be excluded. It also cannot be excluded that the localized affections do not injure other parts.

Evaluation as a tool for surveillance:

Feedback for occurrence of bacterial diseases in the flock.

5. Underweight Birds

Pathological-anatomical :

* cachexia, * smaller animals without macroscopical deviations * frequency of attributes shows relations to the weight of birds: Occurrence of Attributes in birds < 900 g (approved and condemned):

birds < 900 g total number of birds

25.0 % 64.7 % 5.4 % 0.6 % 0.4 % 0.3 %

10.3 %

Judgment and applicability as an instrument of surveillance:

* Single bird: The weights of slaughtered birds depend on the average flock weight. So it does not seem possible to fix a lower limit for approving birds in the inspection. * Flocks as a whole: Random samples of approved birds and calculations of the range of weights provide information on the health status of the flocks (coefficient of variation in conspicuous flocks: > 13 %).

6. Mechanical Damage to the Skin, Muscles and Bones

Fractures, haemorrhages, ruptures, parts not removed, contamination.

38

bursitis sternalis affections of skin deep dermatitis pericarditis perihepatitis inflammations of cavity ruptures

9.4 % 69.9 % 11.8 % 0.7 % 1.1 % 0.9 %

38.8 %

Occurrence of Mechanical Damages in Percent after Evisceration:

1985 1987

approved condemned approved condemned

haemorrhages

ruptures, total

palpable fractures

parts not removed (cavity)

contamination

22.8

-

4.3

0.1

0.1

35.7

6.1

13.4

12.0

1.6

29.0

0.6

7.3

0.1

2.2

45.2

3.9

25.3

4.7

_

Judgment: On account of the non-infectious character the affected parts as follows: * no condemnation of any part : attributes < 3 cm. * localized parts : affection connected with reactions of tissue

to be condemned (e.g. swellings, suggillations), inasfar as important parts are not involved and processing is possible.

* carcass as a whole to be : greater affections on several parts of the carcass, condemned without any possibility of further processing: also total

ruptures.

Monitoring the foregoing procedures: by quantifying (more than a certain grade) and localization of the attribute on the carcass.

39

Task of surveillance (count affections with a spread more than 3 cm diameter/bird):

a) Mistreatment of Birds by Personnel: ante mortem

handling affection post mortem

handling affection

haemorrhages ruptures 1)

fractures

catching wings, thighs throwing barrel

catching swellings and jamming haemorrhages on into the wings and drums crates

shackling tarsus (no of birds bleedings) in the line

b) Defects in Processing Machines: ante mortem handling

post mortem affection

ruptures

parts not removed

contami­nation

-

-

trans­port

adjustment of appara­tus not according to the size of birds; improper processing of carcasses in the line

improper processing by apparatus: rupture

water uptake by tissue

improper evisceration; other parts still con­nected to the carcass

contents of the gut and gallbladder

Conclusions

Attributes to be monitored: Judgment of some attributes depends on the spread, intensity, localization and frequency of the affection and so the opinion of the individual inspector influences the result.

Benefits of monitoring defined attributes in a broiler flock: * improved reproducibility of judgment of carcasses * opportunity to determine the reason for damage * instrument of self-control in production and meat inspection.

40

Lesions/Damage Occurring in Meat Inspection: Judgment and Applicability of Monitoring Systems in Broiler Flocks:

attribute

inflam­mation

skin

cavity

organs

underweight birds

mecha- fractures nical

bursitis sternalis

deep der­matitis

scabby skin

heart,liver

damage haemorrhages

ruptures

parts not removed

contaminations

valu­ation

2

1

2

1

1

2

1

2

2

1

1

limits for counting the attributes and judgment, remarks

thickened and affected surroundings

no minimum limit; bacter-aemia cannot be excluded

count attributes

no limit;

>3 cm diameter

bacteriemia cannot be excluded

random samples ; of weights, (range, coeff. of variance)

no limit

> 3 cm diam.

total

no limit

no limit

description of the dam­ages enables counting of the attribute by using it in a presence-absence-examination

1 : to be condemned generally and counted, if present 2: condemnation and counting depends on the spread, intensity and localization of the attribute

41

References

Fries, R., E. Müller-Hohe, D. Neumann-Fuhrmann and E. Wiedemann-König, 1988. Pilotstudie Geflügelfleischhygiene- Fleischhygienischer Teil. Tierärztl. Hochsch. Hannover.

Fries, R., and A. Kobe, 1990. Einfluß der Bandgeschwindigkeit in Geflügelschlachtbetrieben auf die Ausleseeffektivität der Kontrolle. Tierärztl. Hochsch. Hannover.

Statistisches Bundesamt, 1989. Fleischhygienestatistik. Land- und Forstwirtschaft, Fischerei, Fachserie 3, Reihe 4.3., Verlag Metzler-Poeschel, Stuttgart

Weiss, H., and S. Klaschka (1990): pers. comm.

42

* o

(0 +-<

sz O) 0)

5 0> 00

•o „ O äS > — o ,-i_ co

a xi s- a .h O (O XI

r- <o

r

V ». C T -

-C 60

I 2 3 0*

43

44

GLYCOLYTIC RATE AND SENSORY QUALITY OF TURKEY M. PECTORALIS SUPERFICIALIS - PHYSICAL-CHEMICAL AND MORPHOLOGICAL MUSCLE CHARACTERISTICS

S.J.W. Hillebrand, M. van der Leun, F.J.M. Smulders and P.A. Koolmees

Department of the Science of Food of Animal Origin, Faculty of Veterinary Medicine, The University of Utrecht, P.O. Box 80175, 3508 TD, The Netherlands

Abstract

Thirty-eight turkey toms (approximate live weight 16.5 kg) were stunned using different electrical parameters. A group of 10 animals was selected to include three rates of glycolysis, viz. fast (pH at 15 min post mortem (pHls)<6.0; n=2), moderate (6.0<pH15<6.7; n=5) and slow (pH15>6.7; n=3). The carcasses were chilled in ice water for 2 h. Fibre typing and morphological characteristics of samples excised within lh post mortem were studied microscopically, using enzyme-histochemistry and video image analysis to quanti täte important histological features such as muscle fibre diameter, fibre area, fibre perimeter and shape factor. Tenderness and other physical-chemical quality traits of these muscle samples were assessed, viz. sarcomere length, colour (L, a, b) and drip of uncooked muscles, and shear force and cooking losses of cooked muscles at both 1 and 6 days post mortem. Fast glycolysing muscle seemed to have more intermediate and smaller fibres than moderate and slow glycolyses. In general, higher rates of post mortem glycolysis resulted in longer sarcomeres, lower shear forces and higher colour a-values. Drip and cooking losses were little affected by glycolytic rate. It is concluded that differences in turkey breast muscle tenderness may be related to different glycolytic rates, or to different histological and morphological characteristics, or a combination of both.

Introduction

Several ante- and post mortem factors affect meat quality. Specific knowledge on determinants of turkey meat quality are scarce. Furthermore, the available data are often contradictory. Results of Dodge and Stadelman (1960) indicate that the rates of post mortem glycolysis is important. Stunning influences the rate of glycolysis and may thus be expected to affect meat quality. Compared to non-stunned, "free-struggling" turkeys,

45

showing vehement pre-slaughter muscle action, electrically stunned birds have slower glycolysing breast muscle (Ngoka et al., 1982; Murphy et al., 1988). Results of Murphy et al. (1988) and Goodwin et al. (1961) indicate that electrical stunning has no significant effect on meat quality. Yet other studies (van Hoof, 1979) suggest that in transport-stressed birds, electrical stunning results in more tender breast muscle. Morphological characteristics may, directly or indirectly, influence meat quality. In bovine muscle a negative relationship between fibre diameter and tenderness was reported by Herring et al.(1965). In turkey pectoralis superficialis muscle no such relationship was found (Varadarajulu and Cunningham, 1971). Indirectly, morphological muscle characteristics may be related to meat quality, as they reflect differences in muscle physiology. For instance, the rate of post mortem glycolysis in chicken muscle is related to histological features such as muscle fibre diameter and the prevalence of necrotic changes (Klosowska et al., 1979). In pigs the occurrence of so-called "giant fibres" has been associated with PSE-meat (Cassens et al., 1969; Sosnicki, 1987). In turkey muscle the prevalence of many giant fibres is correlated with toughness (Grey et al., 1986; Seemann et al., 1986). Also, fibre diameter may be relevant for sensory meat quality. For instance, whereas in a study of Smith and Fletcher (1988) fibre type was identical for the entire chicken pectoralis superficialis muscle, fibre diameter varied significantly; the latter was associated with the observed differences in onset of rigor mortis. In contrast, Seemann (1986) reported that the correlation between muscle size and glycolytic rate (onset of rigor mortis) of chicken pectoralis superficialis muscle was negligible. It is conceivable that other morphological features of muscle are associated with meat quality traits and that histological examination might be helpful in establishing the effects of several treatments.By relying on novel techniques such as video-image-analysis histologists can now, with relative ease, conduct morphological studies with a quantitative rather than descriptive character. Purpose of this study was to measure the effects of different glycolytic rates, induced by stunning with different electrical parameters, on turkey meat quality. In addition, the possible relationships between muscle morphology and meat quality traits were determined.

Material and Methods

Thirty-eight turkey toms (approximate live weight ca. 16.5 kg) were electrically stunned in a waterbath. To induce differences in rate of post mortem glycolysis, different electrical parameters were used. The birds were scalded (5 min, 53°C), skinned and eviscerated. The carcasses were chilled for 2 h in melting ice. Subsequently the pectoralis superficialis muscle was deboned, divided in two, vacuum packaged and stored at 0-4°C.

46

Histological/morphological measurements: For histological examination 2, 5 and 3 animals were selected from the fast, moderate and slow group, respectively (vide infra). Muscle samples of 0.5x0.5x0.7 cm were excised from the M. pectoralis superficialis (anterior, middle and posterior location) within 1 h post mortem. These samples were dipped in cryoprotectant, wrapped in aluminum foil and frozen in isopenthane cooled with liquid N2 and then stored at -80°C. From these samples 8-10 ^m thick serial transverse sections were cut with a cryostat (Reichert-Jung, 2800 Frigocut) at -20°C. These sections were stained with an ATPase staining (Bancroft and Stevens, 1982; Szentkuti and Eggers, 1985) for fibre typing. With the microscope, using video image analysis (IBAS, Kontron), the histological features, fibre diameter, fibre area, fibre perimeter and shape factor (supplying information on the fibre-roundness) of 6-15 sections (50 fibres per section) were quantitated. Physical-chemical measurements: At 5 min, 15 min, 30 min, 1 h, 3 h and 24 h post mortem, the pH- and temperature-decline of the M. pectoralis superficialis of all 38 turkeys was measured with a portable pH meter (type CG 818, with a polymère electrode Xerolyt, lot 406-M6-DXK 87/25, Schott Geräte, Hofheim, F.R. Germany) and a digital thermometer (Tastotherm D 700, F.R. Germany). At 1 and 6 days post mortem, a sample from each carcass was unpackaged and sensory quality was assessed. Meat colour of freshly cut muscle sections was measured with a Hunter reflectometer (Cfe L, a, b). A section of the samples was packaged in air-tight plastic bags for measurement of drip loss % (Honikel, 1987). Cuts were cooked in a waterbath at 90°C until a core temperature of 85°C was reached (Pool and Klose, 1969) and cooled with running tap water (ca. 10°C) for 20 min. Cooking losses were assessed by re-weighing muscle samples after cooking. For shear force measurements, rectangular samples of 1 cm2 cross-section were cut at right angles to the muscle fibre direction (Boccard et al., 1981). Subsequently shear forces were measured using a draw-bench (Adamel Lhomargy, Division d'Instruments S.A. Paris, Paris, France) equipped with a Warner Bratzler shearing device. At day 1 randomly located areas in the core of the M. pectoralis superficialis were sampled for measurement of sarcomere length (Koolmees et al., 1986). Data were analysed statistically with the Student t-test.

Results

Stunning with different electrical parameters induced different rates of glycolysis. Based on the pH15 the carcasses were divided into three groups: fast (pH15<6.0, n=9), moderate (6.0<pH15<6.7, n = 15) and slow (pH15>6.7, n = 14) glycolysis. pH and temperature decline of these groups are included in Figure 1. Ultimate pH was not affected by rate of pH-decline.

47

Table 1 Physical-chemical quality traits of fast (pH15<6.0), moderate (6.0<pH15<6.7) and slow (pH,5>6.7) glycolysing turkey pectoralis superficialis muscle.

Trait

Shear force (N/cm2)

Days p.m.

day 1 day 6

Sarcomere length (^m) day 1 Drip loss (%)

Cooking loss (%)

Colour Hunter-L a b L a b

day 1 day 6 day 1 day 6 day 1 day 1 day 1 day 6 day 6 day 6

Glycolytic rate Fast n=9

2.80a* 2.52 1.89a

0.6 0.6 20.8 20.7 48.17 4.95ac

6.07 48.36 5.02 6.98

Moderate n = 15

3.76b

2.27 1.72b

0.5 0.5 22.1 22.5 48.76 4.12b

6.63 49.67 4.33 6.81

Slow n = 14

4.02" 2.52 1.75b

0.4 0.5 24.0 22.2 48.58 4.68bc

6.58 49.62 4.42 6.79

* Figures with superscripts not containing a common letter differ significantly (p< .05).

Table 1 includes the results on physical-chemical meat quality measurements. When assessed at 1 day post mortem, the shear force was found to be affected by glycolytic rates, shear force being significantly lower in fast glycolysing turkeys than in moderate and slow glycolysing muscle. These differences in shear force were no longer present when assessed at 6 days post mortem. Fast glycolysing muscles had significantly longer sarcomeres than moderate and slow glycolysing muscles. At day 1 Hunter a-values of fast glycolysing muscle were significantly higher than those of moderate and slow glycolysing muscle. Differences in Hunter L- and b-values, as well as drip- and cooking losses, were negligible. Morphological studies of fast, moderate and slow glycolysing muscle were conducted on randomly selected animals, 2, 5 and 3 carcasses, respectively. With regard to sensory quality traits the 10 selected turkeys exhibited values similar to the group average.

48

Table 2 Fibre types (i.m. intermediate, wh.=white) and morphological variables (mean values) of muscle fibres at three locations in the M. pectoralis superficialis, viz. anterior (a), middle (m) and posterior (p), of a group of 10 selected turkeys, including three rates of post mortem glycolysis, i.e. fast (pH15<6.0), moderate (6.0<pH15<6.7) and slow (pH15>6.7).

Histological variables

Fibre area (^m2) Fibre perimeter (^m) Fibre diameter (urn) Shape factor Fibre type (%) i.m.

wh.

Rate of Fast (n=2)

6475 326 94 0.73 2.4 97.6

glycolysis Moderate (n=5)

7466 350 100 0.72 1.0 99.0

Slow (n=3)

7165 343 99 0.73 <1.0 >99.0

Muscle location a

8065 362 104 0.73 1.6 98.4

m

7000 340 98 0.73 1.2 98.8

P

6490 328 94 0.72 <1.0 99.0

In Table 2 the results of measurements of the histological and morphological parameters of the muscle fibres from M. pectoralis superficialis of the 10 selected turkeys are presented. No red fibres were observed in the three locations of the pectoralis superficialis muscle. Muscle of fast glycolysers had more intermediate fibres in the anterior part of the breast muscle (5-7 %) than muscle from moderate and slow glycolysers (< 1 %). Also, the fast glycolysers had smaller fibres (area, diameter and perimeter) in the anterior and middle location than the moderate and slow glycolysers. The largest fibres were found in the anterior part of the muscle, the smallest in the posterior part. No differences in fibre shape factor were observed between muscle locations, nor between muscles with different glycolytic rates.

Discussion

In our study fast glycolysing muscles were more tender and had smaller fibres than moderate and slow glycolysing muscles. In the chicken pectoralis superficialis muscle a similar relation was found between the rate of glycolysis and fibre diameter; the onset of rigor in the anterior location was faster (Papa and Fletcher, 1988) and the fibre diameter smaller (Smith and Fletcher, 1988) than in the posterior location. In our study fast glycolysing muscle seemed to have more intermediate fibres, which have higher SDH-activity, than moderate and slow glycolysers. Klosowska et al. (1979) found similar results in chicken breast muscle.

49

In general, a higher rate of post mortem glycolysis resulted in longer sarcomeres and lower shear forces, i.e. more tender meat. It is reported that chilling turkey breast muscle too fast or too slow may lead to cold- and heat shortening, respectively (Smulders et al., 1990). In the present study heat shortening was probably prevented by the high chilling rate. This illustrates the great importance of adapting a chilling rate to the rate of post mortem glycolysis, which among other factors, is affected by the method of stunning. The colour a-value of fast glycolysing muscle is significantly higher in muscles of moderate or slow glycolysers. Froning et al. (1978) observed that breast muscles of animals with a higher rate of post mortem glycolysis had a higher colour a-value than those of slow glycolysing control turkeys. The colour a-value indicates the redness of meat, which is mainly influenced by myoglobin and, to a lesser extent, by hemoglobin and the oxygenation level of both these heme-proteins. The higher a-values in fast glycolysers may be the result of the induced low pre-rigor pH-values, slowing down mitochondrial respiration and increasing the oxygenation of myoglobin (Cornforth and Egbert, 1985).

Although the number of samples examined does not allow any definite conclusions, our study does suggest that differences in morphology, in addition to those in glycolytic rate as induced by stunning procedure might affect meat quality characteristics. More samples need to be examined to confirm the results of this pilot-study.

Acknowledgements

This study was supported by Plukon Turkey Processors at Boxmeer, The Netherlands.

References

Bancroft, J.D., and Stevens, A., 1982. Theory and practice of histological techniques. Second edition, Edinburgh, 400-402.

Boccard, J., Buchter, L., Casteels, M., Cosentino, E., Dransfield, E., Hood, D.E., Joseph, R.L., Macdougall, D.B., Rhodes, D.N., Schön, I., Tinbergen, B.J., Touraille, C , 1981. Procedures for measuring meat quality characteristics in beef production experiments; report of a working group of the Commission of the European Communities (C.E.C), Beef Production Programme. Livestock Production Science 8, 385-379.

Cassens, R.G., Cooper, C.C., Briskey, E.J., 1969. The occurrence and histochemical characterization of giant fibres in the muscle of growing and adult animals. Acta Neuropath. (Berl.) 12, 300-304.

50

Cornforth, D.P. and Egbert, W.R., 1985. Effect of rotenone and pH on the color of prerigor muscle. J. Food Sei. 50, 34-35;44.

Dodge, J.W. and Stadelman, W.J., 1960. Relationships between pH, tenderness, and moisture levels during early post-mortem aging of turkey meat. Food Technol. 14, 43-46.

Froning, G.W., Babji, A.S., Mather, F.B., 1978. The effect of preslaughter temperature, stress,struggle and anesthetization on color and textural characteristics of turkey muscle. Poultry Sei. 57, 630-633.

Goodwin, T.L., Mickelberry, W.C., Stadelman, W.J., 1961. The influence of humane slaughter on the tenderness of turkey meat. Poultry Sei. 40, 921-924.

Grey, T.C., Griffiths, N.M., Jones, J.M., Robinson, D., 1986. A study of some factors influencing the tenderness of turkey breast meat. Lebensm. Wiss. u. Technol. 19, 412-414.

Herring, H.K., Cassens, R.G., Briskey, E.J., 1965. Further studies on bovine muscle tenderness as influenced by carcass position, sarcomere length and fiber diameters. J. Food Sei. 30, 1049-1054.

Honikel, K.O., 1987. Wasserbindungsvermögen von Fleisch. Fleischwirtsch. 67, 418-428.

Hoof, J., van, 1979. Influence of ante- and peri-mortem factors on biochemical and physical characteristics of turkey breast muscle. Vet. Quart. 1, 29-36.

Klosowska, D., Niewiarowicz, A., Klosowski, B., Trojan, M., 1979. Histochemische und histologische Untersuchungen am M. pectoralis superficialis mit beschleunigter, normaler und verzögerter glykolyserate in Broilern. Fleischwirtsch. 59, 1004-1008.

Koolmees, P.A., Korteknie, F., Smulders, F.J.M., 1986. Accuracy and utility of sarcomere length assessment by laser diffraction. Food Microstructure 5, 71-76.

Murphy, B.D., Hasiak, R.J., Sebranek, J.G., 1988. Effect of ante mortem electrical stunning on functional properties of turkey muscle. Poultry Sei. 67, 1062-1068.

Ngoka, D.A., Froning, G.W., Lowry, S.R., Babji, A.S., 1982. Effects of sex, age, preslaughter factors, and holding conditions on the quality characteristics and chemical composition of turkey breast muscles. Poultry Sei. 61, 1996-2003.

Papa, CM. and Fletcher, D.L., 1988. Pectoralis muscle shortening and rigor development at different locations within the broiler breast. Poultry Sei. 67, 635-640.

Pool, M.F. and Klose, A.A., 1969. The relation of force to sample dimensions in objective measurement of tenderness of poultry meat. J. Food Sei. 34, 524-526.

Seemann, G., 1986. Beziehungen zwischen der pH-wert-Änderung nach dem schlachten und anderen Fleischqualitätsparametern beim Hänchen. Fleischwirtsch. 66, 604-606.

Seemann, G., Jones, J.M., Griffiths, N.M., Grey, T.C., 1986. Der Einfluß von Lagerdauer und -temperatur auf die Qualität von Putenfleisch. Arch. Geflügelk. 50, 149-153.

Smith, D.P. and Fletcher, D.L., 1988. Chicken breast muscle fiber type and diameter as influenced by age and intramuscular location. Poultry Sei. 67, 908-913.

51

Smulders, F.J.M., Laack, H.L.J.M., van, Blom, T.P., Hillebrand, S.J.W., 1990. Physical-chemical quality traits of turkey breast muscles as affected by early post mortem chilling rate. Proc. 36th ICoMST, Havana, Cuba, 423-427.

Sosnicki, A., 1987. Histopathological observation of stress-myopathy in M. longissimus in the pig and the relationship with meat quality, fattening and slaughter traits. J. Anim. Sei. 65, 584-596.

Szentkuti, L. and Eggers, A., 1985. Eine zuverlässige Modifikation der Myosin-ATPase-Reaktion zur histochemischen Darstellung von drei Fasertypen in der Skelettmuskulatur von Schweinen. Fleischwirtsch. 65, 1398-1404.

Varadarajulu, P. and Cunningham, F.E., 1971. A histological study of turkey meat as related to sensory characteristics. Poultry Sei. 50, 1144-1149.

52

7.00

A 45

B

6.50

6.00

i^

\

U n

d E 0) 20

15

10

5.50 0 30 60 90 12 J 150 180 24

-Time p.rrurmn.) (h.)

0 30 60 90 120 150 180 24

Time p.m.(mm.) (h.)

Figure 1 pH decline (Fig. 1A) and temperature decline (Fig. IB) of M. pectoralis superficialis of fast (a; pH15<6.0; n=9), moderate (b; 6.0<pH15<6.7; n=14) and slow (c; pH,5>6.7; n = 14) glycolysing turkeys.

53

54

QUALITY INSPECTION EN THE NETHERLANDS

J.J.A. Kroon

General Inspection Service, Ministry of Agriculture, Nature Management and Fisheries, P.O. Box 234, 6460 AE Kerkrade, The Netherlands

Abstract

The General Inspection Service, is responsible for the enforcement of laws, Ministerial directives and regulations of Commodity and Industry boards. To achieve that purpose it carries out inspections.

Introduction

The General Inspection Service (AID) is a special service instrument of the Ministry of Agriculture, Nature Management and Fisheries and operates under the authority of the Secretary-General of the Ministry.

The responsibilities of the General Inspection Service are: - to enforce regulations laid down for those concerned with the production, treatment,

processing, transport, trade, usage, import or export of the products of agriculture and fishery in so far as these regulations have been laid down under the responsibility of the Minister. To enforce those regulations the Minister has authorized the AID.

- to give advice about the inspection aspects of the various regulations as meant in the above paragraph.

The AID employs 650 officers whose activities are divided among three regional inspection districts and a central Investigation Branch. This central Investigation Branch operates on a national level. The AID is assisted by 215 inspection officers employed in other departments of the Ministry and an additional 200 inspection officers employed in the field of environmental legislation.

On the basis of the Industrial Organization Act AID officers are authorized to enforce the regulations of commodity boards and industrial boards.

55

Quality and Water Content

AID officers are authorized to enforce the Quality Requirements and Labeling Ordinance and the EC Water Content Ordinance 1981 of the Industrial Board for the Poultry Trade and Processing Industry.

A. In the Quality Requirements and Labeling Ordinance of the Industry Board for Poultry and Trade standards are laid down for slaughtered fowl, ducks, turkeys, geese, guinea fowl and quail as to:

1. Way of dressing: - 'New York dressed' - 'Eviscerated' - 'Full-dressed' - 'Grilled Chicken' - 'Ready-to-cook'

2. Quality grade : 'A', 'B' and 'C' based upon: - conformation - fleshing - fat covering - pin-feathers - damages to the skin - freezer burns

3. Moisture content in frozen or deep-frozen slaughtered ducks, turkeys, geese, guinea fowl and quail.

The ordinance lays down that frozen or deep-frozen slaughtered poultry shall have a moisture content not exceeding 8% of the weight of the inspected carcasses.

4. Weight: per consumer unit of cuts in kilograms and/or grams - whole carcasses by weight class

if under 1100 grams their actual weight must be within 25 grams under or above the nominal weight if over 1100 grams their actual weight must be within 50 grams under or above the nominal weight

56

- for poultry cuts by weight class. The minimum weight is: weight classes 5 and 50 g 50 and 100 g 100 and 200 g 200 and 300 g 300 and 500 500 and 1000 g > 1000

Limits under nominal weigl 9% 4.5% 4.5% 9g 3% 15 g 1.5%

The previous does not apply if the prepack bears the EC mark.

5. Packaging units and the materials of which they are made must comply to the following requirements: - if they alter the organoleptic properties of the meat they must not be used; - if they transfer noxious substances to the meat they must not be used; - they must be strong enough to protect the meat adequately during transport and

handling; - they may not be reused.

6. With prepacked slaughtered poultry and/or poultry cuts the following information must be provided: - the kind of slaughtered poultry or poultry cuts, named; - the manner of dressing; - the quality grade; - the temperature category (fresh or chilled, frozen, deep frozen); - the net weight or weight class; - the last recommended date for selling at the indicated storage temperature; - information by which the producer, packer or seller can be identified; - the veterinary registration number and - the region of production.

7. The indication that upon violation of the provisions the following disciplinary action may be taken:

- a reprimand (in writing or in person); - a maximum fine of Dfl. 10,000,- per violation, payment of which may be ruled

to be conditional in part or at once; - publication of the disciplinary decision at the offender's expense (which is an

additional sanction).

57

B. The water content of frozen and deep-frozen chickens, hens and cocks is determined in accordance with the provisions laid down in E.E.C. Council Regulation No. 2967/76 dated 23 November 1976 and the E.E.C. Commission Regulation No. 2785/80 dated 30 October 1980.

The above Council Regulation and Commission Regulation are incorporated in the EC Water Content Ordinance 1981 and upon violation of the provisions therein the following disciplinary action may be taken: - a reprimand (in writing or in person); - a maximum fine of Dfl. 10,000,- per violation, payment of which may be ruled to

be conditional in part or in whole; - publication of the disciplinary decision at the offender's expense (which is an

additional sanction).

The samples to be inspected are first checked by means of the rapid detection method (dripping technique) as described in Annex II to the E.E.C. Council Regulation No. 2967/76. If the outcome of the driptest is a value in excess of the limit set down in Annex II, the test is followed by the chemical determination method described in Annex III of the Council Regulation.

Statistics

Quality Requirements and Labeling Ordinance

1990 number of inspec­tions 875

number of cases when summons was served 98

number of warnings 11

EEC Water Content Ordinance 1981

1990 number of inspec- number of cases when number of tions summons was served warnings 15 2

Summonses were submitted to the Poultry Trade and Processing Industry Disciplinary Tribunal to be settled. When water content levels are exceeded warnings are never given but summonses are made directly for submission to the Disciplinary Tribunal.

The Poultry Trade and Processing Industry Disciplinary Tribunal imposed fines amounting to a total of Dfl. 267,750.- over 1990.

58

CARCASS AND MEAT QUALITY OF GAS STUNNED BROILERS

A.B. Mohan Raj and N. Gregory

Department of Meat Animal Science, School of Veterinary Science, University of Bristol, Langford BS18 7DY, U.K.

Abstract

Tlie efficiency of bleeding, the incidence of carcass appearance defects and broken bones and parameters relating to meat quality were investigated in broilers stunned in transport crates with either carbon dioxide or argon or stunned singly by electricity. The results indicated that gas stunning does not impair bleeding efficiency when the interval between neck cutting and scalding is greater than 60 seconds. Gas stunned broilers had less carcass appearance defects, less breast and leg muscle haemorrhaging and fewer broken bones when compared with electrical stunning. Argon stunning resulted in an accelerated early post mortem glycolysis but did not result in heat toughening or PSE-like condition. The results also indicated that argon stunning would enable filleting of the breast meat within one hour post mortem, provided the breast muscle temperature is lowered to less than 5°C. Overall, gas stunning would provide welfare and commercial advantages.

Introduction

A major advantage of using gaseous stur.uing methods for poultry in comparison with electrical stunning is that the birds can be stunned in their transport crates. This would eliminate the preslaughter stress associated with uncrating and shackling live chickens. Batch stunning of chickens in their transport crates could be done either with carbon dioxide or with anoxia using argon or nitrogen. In both carbon dioxide and anoxic stunning procedures convulsions occur after the loss of consciousness (Mohan Raj, Gregory and Wotton, 1990 and 1991) and so the covulsions would not have any welfare implications. However, the convulsions could affect the initial rate of post mortem glycolysis, and the incidence of appearance defects, muscle haemorrhaging and broken bones in the carcasses. In addition, during gas stunning the increased concentration of carbon dioxide or reduced levels of oxygen in the blood may have physiological effects which could influence the efficiency of bleeding. In this paper we present data from a series of experiments conducted in this laboratory which involved gas stunning of broilers with either carbon dioxide or argon induced anoxia.

59

Materials and Methods

In all the experiments reported in this paper seven to eight week old Ross broilers obtained from commercial processors were used. They were fasted overnight prior to slaughter unless specified otherwise. In experiment 1 broilers were stunned singly in a cage, whereas in the other experiments the birds were stunned in batches of ten per crate (80 x 50 x 28 cm). The cages or the crates were loaded on to a lift which descended in 18 seconds into a well containing the stunning gas. The broilers were exposed to a concentration of either 45% carbon dioxide in air (with 9% residual oxygen) or 2% oxygen (air displaced by argon). During this period the gas concentration was continuously measured using gas analyzers (Model 1275 for carbon dioxide and Model 1175 for oxygen; Servomex). Electrical stunning was performed by using a waterbath stunner delivering a constant current (50 Hz in the form of a sinusoidal wave) for four seconds. Bleeding was performed by a manual unilateral neck cut aiming to severe one carotid artery and one jugular vein, and the bleed-out time was 2 to 3 minutes. Wherever dressing of the carcasses is reported in this study, it was performed by scalding at 51°C for 2 minuets and plucking with an automated plucker (Cope and Cope, Reading). Evisceration was performed manually. pH was measured on the pectoralis major muscle by using a temperature compensated pH meter with a combination spear electrode (Russell pH Ltd, Fife, Scotland).

Experiment 1 : Efficiency of Bleeding

In total 110 broilers with a mean liveweight of 3.1 kg (S.D. + 0.4) were used in this study. Forty five broilers in each treatment were stunned with either carbon dioxide or electrical stunning. Within the electrical stunning treatment group 25 birds were stunned with 104 mA (mean + S.D.= 104.2 + 2.5) and 20 birds were stunned with 77 mA (mean + S.D.= 77.7 + 7.8) to obtain birds with non-fibrillated hearts. In addition, 20 broilers were stunned with argon. Soon after stunning the cardiac function of the broilers was evaluated from an electrocardiogram using a Mingograph recorder. Immediately after neck cutting the weight of the blood leaving the carcass was monitored continuously for three minutes by collecting it in a bin placed on an electronic balance. A computer programme (BBC- micro) collected the data and later calculated the cumulative blood loss, expressed as g/kg liveweight, every 10 seconds. During neck cutting some of the birds had their oesophagus cut, which resulted in the contamination of the blood with the crop contents, and these birds were deleted from the statistical analysis. The data were grouped into four treatment groups according to the stunning method and the bird's cardiac function. They were: carbon dioxide (non-fibrillated), argon (non-fibrillated), electrical fibrillated and electrical non-fibrillated. The data were subjected to a one way analysis of variance to determine the significance of the differences between the mean bleed-out proportions and are presented in Table 1.

60

Experiment 2: Carcass appearance defects and meat quality

Two replicates of 120 broilers were used in this study and replicate 2 birds were not fasted overnight. Within each replicate, 40 broilers were stunned in each of the three stunning methods, carbon dioxide, argon or electrical. Electrical stunning was performed with 107 mA (S.D. + 1) current applied for 4 seconds. In both replicates, after bleeding and scalding, one half of the broilers from each stunning method were hand plucked and the other half were mechanically plucked. From each batch of 10 broilers, five carcasses were eviscerated manually and the other 5 were left uneviscerated. All the carcasses were chilled overnight (1°C) and then assessed for external appearance defects as described by Gregory and Wilkins (1989). The eviscerated carcasses were used for pH measurements at 20 minutes and 24 hours post mortem, and cooking loss and texture measurements, whereas the uneviscerated carcasses were used for the assessment of the incidence of broken bones, muscle haemorrhaging and meat colour by using a Minolta Chromometer II Reflectance Meter with an illuminant C light source. To determine cooking loss eviscerated carcasses of known weight were placed in roasting bags and cooked in an electric fan oven at 190°C. Each carcass was cooked to a breast muscle temperature of 90°C. The cooked carcasses were drained for 15 minutes at room temperature and weighed, the loss in weight was expressed as a proportion of the final weight (g/kg). Eight blocks of muscle measuring 20 x 10 x 5 mm in which fibres were all parallel were prepared from cooked and cooled pectoralis major muscle. The force required to compress 4.5 x 10 mm cross sectional area was recorded using a Volodkevitch Analyser (C. Stevens & Son Ltd; St Albans, Herts, England) using a 5 kg load cell and a probe speed of 20 mm/minute. The values are expressed as kg yield force. To compare the effect of stunning methods the data on meat quality from both the hand and mechanically plucked broilers were subjected to a one way analysis of variance. The incidence of muscle haemorrhaging and appearance defects were not subjected to statistical analysis. The overall results are presented in Table 2.

Experiment 3: Incidence of broken bones

The three treatment groups used in this study were argon, carbon dioxide and electrical stunning with 107 m A current applied for 4 seconds. Gas stunning was performed in batches of ten per crate and the birds which were not killed by the stunning gases were not included in the results. A control group of birds were also injected with pentobarbitone sodium (Euthatal; RMB Animal Health) and they were placed in a crate until they all died. The unplucked and uneviscerated carcasses were trimmed of their necks and feet, and frozen in crates before dissection. At dissection the skeletons were assessed for broken bones.

61

Experiment 4:

4a. Breast meat texture after argon stunning and air chilling of carcasses

In total, 100 broilers were used in this study, of which, 80 were stunned in batches of ten per crate with argon and the other 20 were electrically stunned with 107 m A for 4 seconds. Two batches of broilers were allocated to each of the following filleting treatment groups, with filleting being performed at 2, 3, 5 and 21 hours (21h=argon control) post mortem. The electrically stunned broilers were filleted at 21 hours post mortem (electrical control). After taking the pH of pectoralis major muscle at 20 minute post mortem all the carcasses were subsequently stored at 1°C. The rate of chilling of six randomly chosen carcasses was measured using a multichannel Squirrel meter/logger (Grant Instruments Ltd., Cambridge). At 2, 3 and 5 hours post mortem the carcasses of the gaseous stunned broilers were moved to ambient temperature and the entire right breast (pectoralis major and minor with the skin covering) was dissected from each carcass. Each one of these fillets was inserted into a low density polythene bags and stored until they were due to be cooked. At 21 hours post mortem the argon control and electrical control breasts were separated from the carcasses. The pH of the left pectoralis major muscle was measured at the time all the breasts were separated from the carcasses. At 24 hours post mortem each breast was wrapped separately in tin foil and cooked in an electric fan oven to a muscle temperature of 90°C. The texture of a minimum of five blocks of muscle samples were measured as described in Experiment 3.

4b. Breast meat texture after argon stunning and ice chilling of carcasses

One hundred broilers were stunned with argon and the carcasses were processed. At 20 minutes post mortem 80 carcasses of argon stunned broilers were chilled in slushed ice for 30 minutes and twenty carcasses were filleted at each of the following times post mortem: 1, 2, 3 and 24 hours. The other 20 carcasses of argon stunned broilers and 20 electrically stunned broilers carcasses were air chilled overnight and filleted at 24 hours post mortem. Ice chilling of carcasses resulted in a reduction in breast muscle temperature from 38°C to 4°C, and air chilling resulted in a carcass temperature of 2.5°C in five hours. At 24 hours post mortem the pectoralis major muscles were cooked and their texture measured as described under Experiment 3.

62

Results and Discussion

The results of experiment 1 indicated that the gas stunned broilers with non-fibrillated hearts had the same rate of bleeding as the electrically stunned group with fibrillated hearts (Table 1). The electrically stunned broilers with non-fibrillated hearts bled out more during the initial 60 seconds and the difference between this group and the others were significant. After the first minute all the four treatment groups had similar bleed out proportions.

It is possible that the gas stunned broilers might have had a dysrhythmic heart function, which led to slower rate of bleeding. It has been reported that the carbon dioxide inhalation in chickens resulted in a fall in both systolic and diastolic blood pressure and bradycardia (Zeiler et al., 1988) and hypoxia had a similar effect (Richards and Sykes, 1967). Theoretically these physiological effects of hypercapnea and hypoxia would impede the bleeding efficiency, but the results of this study have shown that these effects of stunning gases were not sufficient to impede the bleeding efficiency of broilers, provided that the interval between neck cutting and scalding was not less than 60 seconds. The results of experiment 2 are presented in Table 2. The pectoralis major muscle of electrically stunned broilers had the highest mean pH at 20 minutes post mortem with argon the lowest and carbon dioxide stunned broilers intermediate. The differences between the three means were significant (P< 0.001). The wing flapping (anoxic convulsions) of broilers in argon stunning were relatively more when compared with carbon dioxide stunning and this resulted in accelerated early post mortem glycolysis in argon stunned broilers, but it did not result in a PSE-like condition. However, the accelerated glycolysis with argon stunning did not affect the texture of breast meat and this contrasts with the other reports which have suggested that accelerated early post mortem glycolysis usually results in tougher meat (Lee et al., 1979). The effects of the stunning treatments on the ultimate pH were small, and so they would not be expected to have any adverse effect on the keeping quality. The drop in pH between 20 minutes and 24 hours post mortem was significantly different between the stunning treatments and all three means differed significantly from each other (P<0.001). The anoxic convulsions occurring during argon stunning probably accelerated the onset of rigor mortis and it is likely that these carcasses went into rigor before 20 minutes post mortem. However, this had no adverse effect on the meat quality. On the contrary, argon stunned broilers had slightly more tender breast meat (P<0.05) than the breast from the other two stunning methods. The carbon dioxide stunned broilers had a relatively slower rate of glycolysis and the fall in pH between 20 minutes and 24 hours post mortem was intermediate between argon and electrically stunned broilers.

63

Among the colour parameters L* and a* varied between stunning methods (P<0.05 and P<0.01, respectively), however, these differences were small and may not have had an effect on acceptability of the carcasses. The incidence of carcass appearance defects were similar in all three stunning methods and there was no indication that these defects can arise from the convulsions which occur during gas stunning. None of the gas stunned broilers had breast muscle haemorrhaging whereas it occurred frequently in the electrically stunned broilers. A possible explanation is that the wing flapping in broilers is an act very similar to that of flight and the breast muscles are morphologically designed to cope with it over a short period of time. The tonic spasm induced by electrical stunning appears to be relatively more detrimental to meat quality. The results of experiment 3 indicated that the incidence of broken bones per bird was very much lower in the gas stunning methods when compared with electrical stunning (Table 3). It is apparent that the wing flapping with the gas stunning methods did not result in excessive broken wing bones. By contrast, the incidence of broken pectoral bones in gas stunning was low when compared with electrical stunning. The results of experiment 4a indicated that with argon stunning, filleting the breasts at 2 and 3 hours post mortem after air chilling resulted in slightly tougher meat when compared with filleting at 5 hours or 21 hours post mortem (Table 4). Electrically stunned birds which were filleted at 21 hours post mortem had a texture similar to that of argon stunned broilers filleted at 5 and 21 hours post mortem. It was not certain whether the improvement in texture of argon stunned broilers was an effect of aging overnight or due to the progressive fall in muscle temperature from 10°C at two hours post mortem to 8°C and 2.5°C at three and five hours post mortem, respectively.

The texture value of 2.97 kg yield force reported for breasts filleted at 2 hours post mortem after argon stunning is considerably lower than the texture value of 6.65 kg yield force reported for breasts filleted at 2.5 hours post mortem from electrically stunned broilers (Jones and Grey, 1989). However, in Experiment 4b in which the carcasses were chilled in ice and filleted at 1, 2 and 3 hours post mortem they all had a texture value very similar to that of breasts filleted at 24 hours post mortem after argon stunning or electrical stunning (Table 5). In this experiment 4, the result clearly showed that neither cold shortening nor heat toughening occurred in the argon stunned broiler carcasses. A major constraint in broiler processing operations is the space available for chilling carcasses and storing chilled carcasses prior to portioning and filleting. In addition, the capital investment and the cost of maintaining refrigeration facilities required for overnight chilling, and the cost of handling the carcasses contribute substantially to the production cost. If carcasses were chilled, portioned and filleted within 2 hours of slaughter, the chiller and storage space could be reduced and the products could leave the plant within a shorter time after slaughter. A shorter maturation time after rapid chilling of argon stunned broilers would help to release a considerable part of the storage space used in conventional systems, which could then be used for other purposes, and it would also reduce the cost involved in refrigeration. Although existing EC legislation does not allow the use of slushed ice, in future, a more suitable cooling system using dry ice could be developed.

64

The present series of experiments clearly indicated the advantages of using gases for stunning broilers. It is concluded that, a) gas stunning does not impede with the bleeding efficiency in broilers, provided the interval between neck cutting and scalding is not less than 60 seconds; b) gas stunning improves carcass and meat quality; c) in comparison with electrical stunning, batch stunning broilers with carbon dioxide or argon resulted in a smaller number of birds with broken bones and reduced the number of broken bones per bird; d) stunning broilers with anoxia induced by argon would enable filleting of breast meat at one hour post mortem after lowering its temperature to less than 5°C.

References

Gregory, N.G. and Wilkins, L.J., 1989. Effect of stunning current on carcass quality defects in chickens. Veterinary Record, 124, 530-532.

Jones, J.M. and Grey, T.C., 1989. Influence of processing on product quality, in: Processing of Poultry, Mead, CG. (ed.), Elsevier Applied Science, London, p 127-181.

Lee, Y.B., Hargus, G.L., Webb, J.E., Rickansurd, D.A. and Hagberg, E.G., 1979. Effect of electrical stunning on post mortem biochemical changes and tenderness in broiler breast muscle. Journal of Food Science, 44, 1121, 1122, 1128.

Mohan Raj, A.B., Gregory, N.G. and Wotton, S.B., 1990. Effect of carbon dioxide anaesthesia on the time of onset of unconsciousness and convulsions. Research in Veterinary Science. 49, 360-363.

Mohan Raj, A.B., Gregory, N.G. and Wotton, S.B., 1991 Changes in the somatosensory evoked potentials and spontaneous electroencephalogram of hens during stunning in argon-induced anoxia. British Veterinary Journal. 147, in press.

Richards, S.A. and Sykes, A.H., 1967. The effects of hypoxia, hypercapnea and asphyxia in the domestic fowl (Gallus Domesticus). Comp. Biochem. Physiol. 21, 691-701.

Zeller, W., Mettler, D. and Schatzmann, U., 1988. Studies into the stunning of slaughter poultry with carbon dioxide. Fleischwirtsch. 68, 1308-1312.

65

Table 1 Mean (+ S.E.) bleed-out proportions (g/kg liveweight) in broilers.

Time after Carbon dioxide (non-

neck cutting fibrillated) (seconds)

10 20 30 40 50 60 70 170

n=43

Argon (non-fibrillated) n = 19

Bleed-out (g/kg liveweight) 5.5

11.4 15.1 18.0 20.5 22.2 23.9 31.3

0.44 0.79 0.91 0.95 0.94 0.95 0.93 0.68

6.5 13.1 17.6 20.6 22.6 24.1 25.2 30.5

0.70 1.17 1.52 1.60 1.59 1.58 1.54 1.18

Electrical (fibrillated) n=35

6.4 12.5 16.4 19.4 21.8 23.8 25.5 32.6

0.40 0.63 0.83 0.95 1.02 1.05 1.08 1.23

Electrical (non-fibrillated) n=6

9.7 19.7 25.0 27.7 29.3 30.5 31.3 33.4

1.58 2.82 3.73 3.93 3.99 4.10 4.07 4.42

Probability df=99

0.008 0.002 0.003 0.007 0.023 0.038 0.08 0.53

Table 2 Comparison of stunning and plucking methods on meat quality of broilers.

Stunning method:

pH 20 minutes pH 24 hrs pH 20 min - 24 hrs Cooking loss (g/kg) Texture (kg force) L*

Carbon dioxide n = 40 Mean

6.39 a 5.77 a 0.62 a

26.25 a 2.02 a

54.77 a

S.E.

0.05 0.02 0.04 0.54 0.10 4.09

Argon n = 38 Mean

5.91 b 5.81 ab 0.10 b

26.07 a 1.80 b

52.74 b

S.E.

0.04 0.02 0.03 0.43 0.10 4.11

Electrical n = 40 Mean

6.56 c 5.83 b 0.73 c

25.99 a 2.19 a

54.75 a

S.E.

0.03 0.11 0.03 0.50 0.14 2.97

Sig. of diff.

*** * *** NS * *

1.49 a 0.12 2.06 b 0.10 1.79 ab 0.13 ** -0.25 a 0.22 -0.44 a 0.22 -0.31a 0.18 NS

Appearance defects + 17

Haemorrhaging in breast 0

Haemorrhaging in legs 3

18

0 1 0

19

36 18

+ n = 80 per stunning method Means without a common superscript in a row differ significantly NS = not significant; * = P<0.05; ** = P<0.01; *** = P<0.001.

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Table 3 The effects of stunning methods on the incidence of broken bones.

Slaughter methods Carbon

Argon dioxide Electrical Pentobarbitone

Number of birds killed 92 Percentage of birds with one or more broken bones 11 Broken bones per bird 0.14

Broken bones + per 100 birds: Wing bones 10 Pectoral bones 2

72 100 50

17 0.26

9 3

39 0.63

8 47

14 0.14

0 2

+ Wing bones included humerus, radius and ulna; pectoral bones included scapula, coracoid and furculum.

Table 4 Meat quality variable of pectoralis major muscle filleted at different times post mortem.

Filleting time n

pH 20 minutes pH at filleting Texture

% incidences in > 1 kg to 2 kg >2 kg to 3 kg > 3 kg to 4 kg > 4 kg to 5 kg

Argon 2h 20

5.83 a 5.59 a 2.97 a

3h 20

5.89 a 5.59 a 2.55 b

texture class: 10 40 45 5

15 70 15 0

5h 20

5.85 a 5.62 ab 1.90 c

85 10 5 0

21 h 20

5.81 a 5.68 b 1.90 c

70 30 0 0

Electrical 21 h 20

6.65 b 5.58 a 1.98 c

60 40 0 0

Significance of differences between means

*** * ***

Means without a common superscript in a row differ significantly (P<0.05). * = P<0.05; *** = P<0.001.

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Table 5 Texture of cooked breast fillets from broilers stunned with anoxia and chilled in ice.

Stunning method

argon argon argon argon argon electrical

Chilling method

ice ice ice ice air air

Filleting time post slaughter

1 2 3 24 24 24

n

20 20 20 20 20 20

Texture mean

1.71 1.55 1.75 1.58 1.49 1.57

S.E.

0.10 0.10 0.09 0.05 0.05 0.07

The mean texture values were not significantly different from each other.

68

AN IMMUNOLOGICAL METHOD TO ASSES PROTEOLYTIC BREAKDOWN OF DESMIN, A STRUCTURAL MYOFIBRILLAR PROTEIN, IN BROILER BREAST MEAT

F.J.G. Schreurs

Spelderholt Centre for Poultry Research and Information Services, Agricultural Research Service, 7361 DA Beekbergen, The Netherlands

Abstract

The possibility of using (commercially available) antibodies in the detection of degradation of desmin was investigated. It was concluded that immunological detection by means of "western blotting" could be a useful tool in the study of degradation of specific proteins in muscle. Subjects of future research are pointed out.

Introduction

It is long known that meat tenderizes upon storage (Lehmann, 1907), however the exact mechanisms of this phenomena are greatly unknown. In general several proteolytic enzymes are held responsible for the tenderizing effect of meat storage. The most important endogenous proteases which are believed to be involved in post mortem protein breakdown are the Calcium activated neutral proteases (Calpains) and several acid proteases called Cathepsins. The calpains show their optimal enzymatic activity in the neutral pH region but at pH values usually found in conditioned meat (around 5.5) they still have a considerable part of their original activity left. There are believed to be two forms of Calpains. One form needs about 20 pM Ca2+-ions to exhibit a half maximal activity (Dayton et al., 1981).It is therefore called /i-CANP (Calcium Activated Neutral Protease) or Calpain I. The second form of calcium activated neutral protease is also called m-CANP or Calpain II and exhibits its half maximal activity at 1 - 2 mM Ca t ­ions (Dayton et al., 1976), a concentration several orders of magnitude higher than the physiological concentration of Ca2+ within the cell. The former plays an important role in meat tenderness (Koohmaraie et al., 1986). There is evidence that the latter is a precursor of the former. Limited autolysis of chicken skeletal muscle Calpain II yielded intermediate products with a Ca2+ sensitivity comparable to that of Calpain I (Murachi, T., 1983).

69

Cathepsins are proteolytic enzymes which show an optimal enzymatic activity at pH values in the acid region. In relation to meat quality the most important catheptic enzymes are believed to be Cathepsins A, B, C, D, H and L. The types B, C, H and L are thiol proteases while the A and D type are aspartic proteases. The former are capable of degrading native proteins. The A and C type are only capable of degrading short peptides and probably play a role in cleaning up degradation products of other proteolytic enzymes (Mycek 1970). Meat tenderization and some other changes of functional properties during ageing are attributable to proteolytic processes in the muscle. Some of the observed changes are: - Z-line degradation. - Degradation of troponin-T and simultaneous appearance of 30 kD degradation products. - Degradation of several different structural myofibrillar proteins (e.g. desmin and a-

actinin) - Degradation of gap filaments (e.g. titin). - Appearance of a 95 kD degradation-product of unknown origin. - Increase of Mg2+ and Ca2+ dependent ATP-ase activity of myofibrils. - Alteration of myosin-actin interaction. The above mentioned proteolytic processes are mostly observed in mammalian tissue and not very clear. Most of them are based on (electron) microscopic observations or Sodium Dodecylsulphate-Polyacrylamide gelelectrophoresis (SDS-PAGE). It is very difficult to correlate the observed macroscopic changes with the breakdown of a specific protein. Due to lack of sensitivity SDS-PAGE is only of limited value in the study of post mortem proteolytic changes in poultry meat. Demonstration of the (dis)appearance of a major component is possible but changes in minor components are very difficult to detect. Immunochemical methods can be much more sensitive and they have the advantage of large specificity. It is possible to combine these advantageous properties of antibodies with the above mentioned techniques. It is possible to transfer the electrophoretically separated proteins to nitrocellulose membranes. The technique was originally developed for RNA and DNA which is called "Southern blotting" (Southern, 1975) and "Northern blotting" respectively. Towbin et al. (1979) adopted the technique for the transfer of proteins separated by urea-polyacrylamide gelelectrophoresis and Burnette (1981) modified the method for blotting of SDS-PAGE separated proteins. This technique was called "Western blotting" by the latter author and this name is adopted by the scientific community ever since. Although direct detection of antigens in SDS Polyacrylamide gels is possible (Olden and Yamada, 1977) it is difficult and insensitive due to the slow diffusion of large immunoglobulin molecules ( 150 kD) into the relatively small pores of the Polyacrylamide gels. The abovementioned "western blotting" technique is much easier and more sensitive. The proteins are absorbed to the nitrocellulose and readily available for binding to specific antibodies. Originally radiographic detection methods were used but since then less troublesome detection methods were developed such as immunoenzymatic staining. In this technique the antibodies are labeled with an enzyme (e.g. peroxidase or alkaline phosphatase) capable of conversion of a chromogenic substrate.

70

These enzyme-antibody conjugates can also be used in histological studies of muscle tissue. For more information on this subject see Avrameas (1972). In recent years a few results of research were published which was conducted on the immunochemical detection of post mortem proteolytic changes in beef. Weber (1984) and Wismer-Pedersen and Weber (1987) published results of studies on the changes in desmin and Z-disk actin during aging using SDS-Page, immunoprecipitation and enzyme linked immunosorbent assay (ELISA) to quantify the degradative processes. They conclude that the "improvement in tenderness of beef is related to degradation of desmin. The concentration of desmin degradation products in Potassium iodide (KI) extracts of myofibrils can be determined by competitive ELISA. The difference in concentration of the degradation products between fresh slaughtered and aged meat can be used as an immunological ageing index." Bandman and Zdanis (1988) used antibodies against myosin heavy chain (MHC) and titin to investigate the degradative processes in beef. They found virtually no degradation of MHC during prolonged ageing at 4°C but when incubated at 37°C the MHC rapidly is broken down into immunologically detectable peptides. Monoclonal antibodies against titin show a breakdown of this protein during storage at 4°C and after 2 to 3 weeks after slaughter no undegraded titin is detectable. Hence, it seems worthwhile to investigate the possibilities of immunochemical detection methods in the study of proteolytic degradation of meat proteins.

Object of this study was to investigate whether commercially available antibodies can be used to detect the degradation of desmin from chicken myofibrillar proteins by proteolytic enzymes.

Materials and Methods

Materials

All chemicals used were analytical grade. Regular laboratory chemicals were purchased from Merck, Darmstadt, Germany. Proteolytic enzymes were purchased from Sigma chemical Co, St. Louis, USA. Desmin monoclonal antibodies and goat-anti-rabbit-alkaline-phosphatase conjugate was from Boehringer Mannheim, Germany. Desmin polyclonal and monoclonal antibodies and goat-anti-mouse-alkaline-phosphatase as well as goat-anti-rabbit and goat-anti-mouse peroxidase conjugates were from Sigma chemical Co. Diaminobenzidine, Bromo-chloro-indolyl-phospate and nitro-blue tetrazolium were from Sigma chemical Co. Polyacrylamide gels (stacking gel: 6% total Polyacrylamide, 3% cross-link; separating gel: 2% cross-link, total Polyacrylamide linear gradient 10 - 15%) were purchased ready for use from Pharmacia, Uppsala, Sweden. Reinforced nitrocellulose membranes,type BAS 83, were from Schleicher & Schuell, Den Bosch, The Netherlands.

71

Equipment

Homogenisations were carried out with a Polytron PT3000 homogeniser from Kinematica, Luzern, Switserland. Electrophoretic experiments were carried out on a Phastsystem gelelectrophoresis system from Pharmacia. Electrophoretic transfer was carried out at the Phastsystem with a Phasttransfer semi-dry blotting assembly of Pharmacia. Stained gels and western blots were evaluated using the Phastimage image analysing apparatus of Pharmacia.

Preparation of glycerinated myofibrils

Glycerinated myofibrils (GMF) were produced from pre rigor broiler breast meat obtained from a local processing plant immediately after slaughtering. The method used was described by Knight and Trinick (1982). The conserved myofibrils were stored at -20°C until further use.

Proteolytic experiments

Before incubation with proteolytic enzymes the GMF were exhaustively washed with phosphate buffered saline. The last two washes were carried out with the buffer used for incubation with the proteases. Proteolytic enzymes used were Calcium activated neutral protease (CANP), papain, nagarse, trypsin and pepsin. They were dissolved to a total activity of 5 U/ml (activities as stated by the manufacturer) in the appropriate buffer. Buffers used were for CANP 50 mM phosphate pH 7.2 with 5 mM CaCl2, for papain 50 mM phosphate pH 6.8, for nagarse 50 mM phosphate pH 7.5, for trypsin 50 mM Tris pH 8.0, and for pepsin 50 mM Maleic acid pH 2.0. To 990 1 of a suspension of 2 mg/ml myofibrils 10 /J of the respective protease solutions were added. To the blank 10 /A of the appropriate buffer was added. The samples were incubated in a shaking waterbath at 37 ± 0.2°C for 0.5, 1, 2, 3, 4, 5 and 6 hours respectively. At the end of the incubation period the samples were transferred to an ice water bath for 5 minutes and then centrifuged for 5 minutes at 12,000 x g. The supernatants were decanted and stored at -20°C until needed. The sediments were resuspended in ice cold PBS and again centrifuged at 12,000 x g. The supernatants were aspirated and the sediments were used in the electrophoretic experiments.

72

SDS-polyacrylamide gelelectrophoresis

Prior to electrophoresis the sediments obtained after incubation with proteases were dissolved in 0.5 ml sample buffer containing 60 mM Tris pH 6.8, 1 mM EDTA, 2% Sodium dodecyl sulphate, and 10% glycerol. Protein concentrations were measured using the method described by Smith et al. (1985). The total protein concentration in the sample was adjusted to 2 mg/ml and to 90 y\ alliquots of these samples 10 /d of a solution of 0.1% bromophenol blue and 0.5 M Dithioerythrol was added. The samples were heated for 5 minutes at 100°C in a heating block and centrifuged at 12,000 x g for 5 minutes. 1 ni samples were applied to the Polyacrylamide gel by means of a phastgel 8/1 sample applicator which can carry 8 samples. The gels were run for 65 volthours after which they were ready either for transfer to nitrocellulose membranes or total protein (silver) staining according to Heukeshoven and Dernick (1985).

Western blotting

Blotting buffer used was a 25 mM Tris, 192 mM Glycine, 20% Methanol buffer according to Gershoni and Palade (1982). Total protein stains were carried out according to Kovarik et al. (1987). The blots used for specific immunostaining were blocked with 80% horseserum/20% ethanol. Dilutions of the primary antibodies were made according to manufacturers directions in 4% normal goat serum in Tris-buffered saline of pH 7.2. The blots were incubated with the primary antibodies and secondary antibody-enzyme conjugates for 1 hour. Blots incubated with peroxidase conjugates were stained with diaminobenzidine with metal ion enhancement according to Harlow and Lane (1988). Alkaline phosphatase conjugate incubated blots were stained with bromo-chloro-indolyl-phosphate/nitro-blue tetrazolium substrate according to Harlow and Lane (1988).

Results

The incubations of myofibrils with Calpain show a gradual decrease in intensity of the desmin band in the western blots. A typical example is shown in Figure 1. The first lane shows the untreated myofibrilar proteins. The densely stained band is the desmin band. The lightly stained band is probably the stroma-actin or z-band actin mentioned by Weber (1984) to give cross reactions with desmin. The measured molecular weight of 42 kD supports this assumption. At this stage it is not clear wether the cross reactivity is due to antigenic similarity of desmin and z-disk actin or that the antibody was raised against a unpure desmin preparation containing z-disk actin. Due to the low desmin and z-disk actin content of myofibrils and the relatively high protein load in the 40 - 60 kD area on the gel the differences between the incubations are not shown on the total protein stains (Figure

73

2). Image analysis shows an decrease in density of the desmin and z-disk actin. Simultaneously the density of bands of lower molecular weight (36 and 30 kD resp.) not present in lane 1 increases in lanes 2 through 8. Relative band densities are shown in Table 1. The decrease of the original proteins and the increase of the proteolytic fragments is clearly demonstrated. The band with the lowest molecular weight shows an increasing waviness with increasing proteolysis, suggesting generation of multiple fragments in close range of each other. Figure 3 shows the results of an incubation with trypsin. The contents of the lanes are identical to the lanes shown in Figure 1. It is clear that only the sample not incubated with the enzyme contains immunoreactive desmin and z-line actin. The other lanes do not show any immunoreactivity at all. These results reflect those obtained with the other enzymes. Obviously the proteolytic effects with those (in muscle non endogenous) proteases are much larger.

The total protein stains of these incubations show many residual protein bands left, especially in the higher molecular weight regions, suggesting that desmin and z-disk actin are extremely sensitive to proteolytic degradation in general. In the supernatants of the incubation mixtures a lot of proteolytic fragments are detectable by total protein stains but none of them show immunogenic activity (Results not shown).

Table 1 Change in density of bands (relative peak surface) of desmin and z-disk actin due to proteolysis by calpain.

Incubation-time

Desmin (55 kD)

Z-disk actin (42 kD)

Fragment 1 (36 kD)

Fragment 2 (30 kD)

0 hrs

62.2

37.8

0.0

0.0

hr

53.1

35.7

6.4

4.8

1 hr

52. 7

34. 6

6.4

6.3

2 hrs

51.9

26.2

9.0

12.9

3 hrs

51.4

22.1

13.5

13.0

4 hrs

37.5

21.9

16.1

24.5

5 hrs

23.6

15.5

25.1

35.8

6 hrs

22. 5

6.0

30. 0

41. 5

The blots which were immunostained with monoclonal antibodies failed to detect any desmin, even in the non digested sample (results not shown). Obviously the epitopes against which the antibodies were directed did not stay intact during processing of the samples (e.g. denaturation by SDS and dithioerythrol).

74

Conclusions

The experiments with calpain digestion of myofibrils show a gradual digestion of desmin and z-disk actin. This is in agreement with earlier findings (Weber, 1984; Wismer-Pedersen 1987). The polyclonal antibodies proved to be useful in detecting degradation of desmin in myofibrillar samples. The monoclonals could not be used with the electrophoretic method generally applied with myofibrillar proteins. Future research will be focussed on improving sensitivity and specificity of the detection methods. This could be achieved by using more specific polyclonal antibodies or (mixtures of) monoclonals able of detecting denaturation resistant epitopes. Furthermore the staining can be made more sensitive by using alternative labels like gold colloids (immunogold staining). The methods used look very promising in being able to detect degradation of specific proteins. Other structural proteins than desmin could be important subjects of further research.

References

Avrameas, S., 1972. Enzyme markers: Their linkage with proteins and use in immunohistochemistry. Histochem. J. 4, 321.

Burnette, W.N., 1981. "Western Blotting": Electrophoretic transfer of proteins from sodium dodecyl sulfate-polyacrylamide gels to unmodified nitrocellulose and radiographic detection with antibody and radioiodinated protein A. Anal. Biochem. 112, 195.

Dayton, W.R., Reville, W.J., Goll, D.E. and Stromer, M.H., 1976. A Ca2+-activated protease possibly involved in myofibrillar protein turnover. Partial characterization of the purified enzyme. Biochemistry 15, 2159

Dayton, W.R., Schollmeyer, J.V., Lepley, R.A. and Cortes, L.R., 1981. A calcium-activated protease possibly involved in myofibrillar protein turnover. Biochim. Biophys. Acta 659, 48.

Gershoni, J.M. and Palade, G.E., 1982. Electrophoretic transfer of proteins from sodium dodecyl sulphate-polyacrylamidegels to a positively charged membrane filter. Anal. Biochem. 124, 396.

Harlow, E. and Lane, D. (Ed's.), 1988. Antibodies: a laboratory manual. Cold Spring Harbor laboratory, New York.

Heukeshoven, J. and Dernick, R., 1985. Simplified method for silver staining of proteins in Polyacrylamide gels and the mechanism of silver staining. Electrophoresis, 6, 103.

Knight, P.J. and Trinick, J.A., 1982. Preparation of myofibrils. In: Methods in enzymology. Vol 85. Frederiksen, D.W. and Cunningham L.W. (Ed's) pp. 9. Acad. press, New York.

75

Koohmaraie, M., Schollmeyer, J.V. and Dutson, T.R., 1986. Effect of low-calcium-requiring calcium activated factor on myofibrils under varying pH and temperature conditions. J. Food Sei. 51, 28.

Kovarik, A., et al., 1987. An improved colloidal silver staining method of protein blots on nitrocellulose membranes. J. Folia Biologica (Praha). 33, 157.

Lehmann, K.B., 1907. Studies of the causes of toughness in meat. Arch. F. Hyg. 63, 134.

Murachi, T., 1983. Calpain and calpastatin. TIBS, May 1983, 167. Mycek, M.J., 1970. in: Methods in enzymology, Vol XIX, E. Perlman and L. Lorand

(Eds.) Acad. Press, pp. 285 - 315. Olden, K. and Yamada, K.M., 1977. Direct detection of antigens in sodium dodecyl

sulfate Polyacrylamide gels. Anal. Biochem. 78, 483. Smith, P.K., Krohn, G.T., Hermanson, G.T., Malia, A.K., Gartner, F.H., Provenzano,

M.D., Fujimoto, E.K., Goeke, N.M., Olson, B.J. and Klenk, D.C., 1985. Measurement of protein using bichinonic acid. Anal. Biochem. 150, 76.

Southern, E.M., 1975. Detection of specific sequences among DNA fragments separated by gel electrophoresis. J. Mol. Biol. 98, 503

Towbin, H., Staehlin, T. and Gordon, J. (1979). Electrophoretic transfer of proteins from Polyacrylamide gels to nitrocellulose sheets: Procedure and applications. Proc. Natl. Acad. Sei. 76, 4350.

Weber, A., 1984. Ageing of bovine muscle: desmin degradation observed via enzyme linked immuno sorbent assay.Proc. 30. european meeting of meat research workers, Bristol.p. 135.

Wismer-Pedersen J. and Weber. A., 1987. Immunochemischer index für die rindfleishreifung. Fleischwirtsch. 67, 351.

76

Figure 1 Western blot of Calpain digest stained with polyclonal anti-desmin antiserum. Lanes 1 through 8: samples incubated with calpain at 37°C for respectively 0, lh, 1, 2, 3, 4, 5 and 6 hours.

« S I * . <4kX» •*-**•"

Figure 2 Western blot stained for total protein. Lanes identical to Figure 1.

77

Figure 3 Proteolytic effects of trypsin.

78

MODEL EXPERIMENTS FOR CLEANING BROILER CARCASSES DURING SCALDING

C.H. Veerkamp, C. Pieterse, N.M. Bolder and L.A.J.T. van Lith

Spelderholt Centre for Poultry Research and Information Services, Agricultural Research Service (DLO), 7361 DA Beekbergen, The Netherlands

Abstract

Experiments were carried out to validate the theoretical model for calculating the bacterial reduction in a cascade of ideal mixed tanks. The measured bacterial counts in all tanks of a three stage scalder, agree with the calculated values from starting the operation up to 2 hours reaching a constant level of contamination. The total decimal reduction of the bacterial load of the carcasses is about 3 log units. The results proved that recirculating of water with pasteurization or increasing water supply has only a small effect on the reduction of microorganisms. The existing scalding operation can be improved by increasing the number of stages in cascade or decreasing the amount of adherent water which is transported with the carcasses from a previous tank to the next one. The model and computer program can be used to optimize existing scalding systems.

Introduction

Modern automated methods of poultry processing are not able to reduce the contamination level of a flock to levels that guarantee absence of potentially pathogenic microorganisms in end-products. To reduce the level of contamination of flocks it is essentially to improve the hygiene in production and transport. Codes for GHP are necessary in the whole production chain of broilers. Several methods are discussed to improve the hygiene in processing. For example by introducing spray cleaning (Mulder and Veerkamp, 1974), regulations (EC and USDA) and the application of the HACCP concept (Fries, 1989) in poultry processing. A review of the hygiene problems and control of process contamination is given by Mead, 1989. Reduction of the initial bacterial load of the flock as soon as possible in the processing plant is important to avoid contamination of carcasses in following processing operations.

79

Immersion of carcasses in water (scalding) seems to be very effective in reducing the initial bacterial load (Mulder and Dorresteijn, 1977). At a scalding temperature of 60°C at least a 100 fold reduction was measured. At lower scalding temperature (50 -52°C) reduction was only 10 fold. Research was started to increase the reduction of microorganisms at low scalding temperatures.

A theoretical model was developed to predict the reduction of numbers of microorganisms in a counter current scalding operation (Veerkamp, 1989, Veerkamp, 1990). Calculations were carried out to estimate the influences of the various parameters with a computer program of the model. These calculations include the influences of adherent water on the carcass, the water supply in the last tank, the volume ratio between water and carcasses, the decimal reduction time and the number of tanks in a cascade. The conclusion was that a cascade of ideal mixed scalding tanks has the potential to improve the operation by reducing the number of microorganisms on the carcasses after scalding. Meanwhile this concept is already partly applied by several equipment manufactures to new designed scalders.

Pilot plants studies were carried out to validate the theoretical model at Spelderholt Centre. The results of these studies are described in this paper.

Materials and Methods

A 3-stage scalder was installed in the Spelderholt pilot plant (Figure 1). The dimensions were comparable to an industrial scalder with a capacity of 1600 broilers / hour. Each stage contained 1500 1 water and total scalding time is about 4 minutes. The water supply was in the last tank. Water flows by tubes from tank 3 to tank 2 and from tank 2 to tank 1. Tank 1 has an overflow to keep the watervolume in the system constant. The water in the tank was agitated by air. A recirculation system was used to increase the waterflow in the tanks and to save water and energy. The plate heat exchanger consisted of a recuperation section (A), a holding section (B) and a heating section (C). Water of tank 1 was heated to 75°C for about 20 s, cooled down to 55°C and supplied to tank 3.

Experiments were carried out with a bacterial suspension flow to tank 1, simulating a constant bacterial input by carcasses. The suspension consisted of a mix of fresh broiler droppings and water, which was homogenized thoroughly during one hour, followed by sieving to discard feed and other concrete particles. Initial total counts of the suspension were approximately 108 to 109 cfu/ml. The supply to the scalding tank was about 7 1 suspension per hour which is equal to about 4xl08 to 4xl09 cfu of microorganisms per carcass, assuming a capacity of 1600 birds/h.

80

The adherent water flow (160 1/h) from tank 1 to 2, tank 2 to 3 and out of tank 3 was simulated with centrifugal pumps and measured continuously by flowmeters. In all experiments the simulated amount of adherent water was 0.1 1/carcass. The temperature in the three tanks was kept at 45 or 50°C, due to the detection level and the expected number of microorganisms in the system. The recirculation flow in the experiments was about 7 times the flow of adherent water and the fresh water supply equal to the flow of adherent water. Bacterial examination of the scald water was carried out at time intervals of 10, 20, 40, 60, 90 minutes and in some experiments also at longer intervals after starting the operation. The samples were taken in the three tanks and the sample containers were immediately chilled in crushed ice. The samples were homogenized, diluted and plated on Plate Count Agar and Violet Red Bile Agar for estimation of respectively total aerobic counts, after incubation at 30°C for 48 hrs and Enterobacteriaceae after incubation at 37°C for 24 hrs.

The reduction of microorganisms was calculated as difference between the logarithmic number of microorganisms simulated to be released from a carcass in the first tank and the logarithmic number of microorganisms present in the adherent water/carcass leaving the scalder.

Results and Discussion

The computer program was used to calculate the influences of the process parameters on the theoretical reductions of microorganisms in a 3 stage scalding system. Figure 2 shows the reductions of microorganisms estimated by these calculations.

Two dimensionless parameters are required to predict the reduction of cfu's of microorganisms. Reduction of the amount of adherent water (Qa) and a lower decimal reduction time (D) increase the number of reductions in the system. Increasing the total input of water (Qt) reduced the residence time (t) in the system and increased the parameter D/t. The ultimate effect on the number of decimal reductions by increasing the waterflow depends of the design parameters of the system.

The results of two experiments are presented. Similar results were obtained in all other experiments. The conditions and the number of decimal reductions estimated in these experiments are presented in Table 1. In experiment B the total cfu-counts were equal to the Enterobacteria cfu-counts so it is assumed that the suspension nearly completely consisted of Enterobacteria.

81

Table 1 Conditions and estimated reduction in cfu-counts of microorganisms in the experiments A and B, scalding temperature = 45°C.

Experiment

Microorganisms

Qt (1/carcass)

Qa (1/carcass)

D(s)

Input (cfu/carcass)

Calculated Reduc­tion (log/carcass)

A

Total count Entero-bacteria

0.1

0.1

36000

3.0xl09

3.0

7200

1.7xl09

3.6

B

Total count Entero-bacteria

0.8

0.1

7200

7.3xl08

3.9

7200

7.3xl08

3.9

In Figures 3 to 5 measured cfu-counts of experiments A and B are presented. The computer program was used to calculate bacterial count in the three tanks after starting the operation up to 2 hrs using the conditions as given in Table 1 and the described equipment parameters. These calculated cfu-counts in relation to the operation time in the 3 tanks are also presented.

The results of the calculated cfu-counts agree in both experiments (A = Figure 3 and 4, B = Figure 5) well with the measured bacterial cfu-counts in all tanks of the scalding equipment. It proved that the model can be used to predict reductions of microorganisms in scald operations.

Comparing experiment A with B, the results indicate that the achieved cfu-count reduction by scalding is only slightly improved by recirculation and pasteurization about 7 times the volume of adhering water per carcass, as was the case in experiment B. A larger volume of water input is comparable to recirculation combined with pasteurization. No effect can be expected from increasing the water input in the scald system. This means only a waste of water and of energy. Comparing the results of Mulder and Dorresteijn, 1977, the reduction of the bacterial load of the carcasses can about 100 times increased by using a 3 stage scald operation at low temperature. The model indicates that the hygiene of the scald operation can be improved by increasing the number of tanks in cascade and by reduction of the amount of adherent water to the carcass. Increase of the dripping time between two tanks and discharging the water in the previous tank may reduce the amount of adherent water substantially. Dividing existing scald equipment in separate tanks increased the number of tanks in cascade and improved the cleaning effect.

82

The model and computerprogram can be used to optimize the design of the scalding equipment.

References

Fries, R., 1989. HACCP in der Geflügelfleischgewinnung. Proceedings Hohenheimer Geflügelsymposium. Editor S. Scholtyssek. Verlag Eugen Ulmer, Stuttgart, pp 83-89.

Mead, G.C., 1989. Hygiene problems and control of process contamination. In: Processing of poultry. Editor: G.C. Mead, Elsevier Applied Science, London, pp 183-220.

Mulder, R.W.A.W. and L.W.J. Dorresteijn, 1977. Hygiene beim Brühen von Slachtgeflügel. Fleischwirtschaft, 57, 2220-2222.

Mulder, R.W.A.W. and C.H.Veerkamp, 1974. Improvements in poultry slaughterhouses, Hygiene as a result of cleaning before cooling. Poultry Science 53, 1690-1695.

Veerkamp, C.H., 1989. A model for cleaning broiler carcasses before and during scalding. Proceedings Hohenheimer Geflügelsymposium. Editor S. Scholtyssek. Verlag Eugen Ulmer, Stuttgart, pp 213-218.

Veerkamp, C.H., 1990. Can we reduce carcass contamination. Poultry International 29, (3), 44-50.

83

A

B

C

R e c i r c u l a t i o n w a t e

i

1

1

1

1

1

C / V

In pu1

4

i i l l i i

I 1 ! i i i i i i i i i ' * i i i

t c a r c a s s

A

A

3 S

;r

/

r 1 l l 1 1 1 ! 1 1 1 1

A o \ l ' 1 ^- 1 1 1 1 1 1 1 1 1 1 1

. _v

/

/

\

W a t e r input

Ù >b

i i 1 1 i i i i i i

A o \ l/ 1 J I 1 1 1 1 1 1 1 1 1 1

V 1

Figure 1 Three stage scalding equipment with heat-exchanger for recirculated water, A recuperation section, B = holding section, C = heating section.

Number of reductions

0.01

Qa / at

Figure 2 Results of theoretical calculations for a 3 stage scalding system.

84

L o g to ta l c f u count

Figure 3 Results of measurements and theoretical calculation of total cfu- counts for experiment A (watersupply is equal to adherent water). Marks are measurements: + = tank 1, A = tank 2 and o = tank 3.

1 0 Enterobacteria (log cfu count)

Figure 4 Results of measurements and theoretical calculation of Enterobacteriaceae cfu-counts of experiment A.

85

1 0 Enterobacteria (log cfu count)

Figure 5 Results of measurements and theoretical calculation of Enterobacteriaceae cfu-counts of experiment B (with pasteurization and recirculation).

86

SESSION M2

NEW USES FOR MEAT COMPONENTS

87

IMPROVING THE FUNCTION AND QUALITY OF MECHANICALLY SEPARATED POULTRY MEAT

H.R. Ball, Jr. and J.G. Akamittath

Department of Food Science, North Carolina State University, Raleigh, NC 27695-7624, USA

Abstract

The polymerization of crude actomyosin (CA) with transglutaminase (EC 2.3.213; R-glutaminyl peptide amine gama-glutamyl transferase) and the rheological properties of polymerized CA were evaluated. CA prepared from mechanically separated turkey meat was incubated with transglutaminase at pH 6 and 7 at 4°C or 37°C. SDS-polyacrylamide electrophoresis revealed that myosin monomer content decreased by 60% after treatment at pH 6 or 7 at 37°C. There was a 30% decrease in free amino groups that was highly correlated (0.95 to 0.99) to the decrease in myosin monomer content. Polymerization occurred at 4°C but at a much lower rate. Polymerization at the lower temperature was greater at pH 6. These results indicate that transglutaminase can be used to covalently cross-link CA. Incubating CA in the presence of the enzyme at 37°Cfor two hours resulted in an increase in the storage modulus (G') or rigidity and decreases in the phase angle indicating the formation of a gel network. Stress relaxation evaluation of the resulting gel at room temperature showed that the network formed was retained. Rheological thermograms for the cross-linked CA were similar in form to thermograms obtained for other actomyosin preparations. Rapid development of G' began at about 55°C with maximum G' during heating being attained at the end of the heating regime. There was further development of G' on cooling to 25°C. Crosslinking CA altered the rheological properties as determined by low strain rheological methods. It is reasonable to expect that polymers of actomyosin will impart altered failure properties (stress and strain at failure) when used to manufacture meat products.

Introduction

"Surimi-like" processing of mechanically deboned poultry meat has been shown to produce a functional meat ingredient (Hernandez et al., 1986; Dawson et al., 1988, 1989, 1989). The washed mechanically deboned poultry meat generally contains less pigment and fat and generally has a bland flavor. When chopped with salt (1 to 2%), it forms

89

strong gels with higher shear stress and strain at failure relative to unwashed mechanically deboned poultry meat (Ball, 1988; Dawson et al., 1990). Hernandez et al. (1986) reported that up to 20% ground turkey meat could be replaced with washed mechanically deboned turkey meat without significantly affecting overall sensory quality of cooked patties.

While washed mechanically deboned poultry meat has useful functional properties, the texture of meat products formed solely with washed meat will be typical of fine chopped meat products. Partial substitutions of ground meat with washed meat can be used (Hernandez et al., 1986) to achieve different textural attributes, but are self-limiting. Improving the functional and textural attributes of washed mechanically deboned poultry meat could possibly allow designed texture of meat products based on washed mechanically deboned poultry meat.

Akamittath et al. (1991) briefly reviewed the potential for using transglutaminase (EC 2.3.213; R-glutaminyl peptide amine gama-glutamyl transferase) to enzymatically modify food proteins, especially muscle proteins in order to improve textural development. It was noted in his review that transglutaminase in Alaska pollack surimi has been suggested as the initiator of low-temperature gelling presumably through polymerization of myosin. Kamath (1990) found that maximum gel strength in surimi sols induced by low-temperature setting was correlated to increases in polymers of heavy myosin.

Transglutaminase catalyzed reaction results in the formation of covalent bonds much stronger than hydrogen and hydrophobic bonds. Cross linking muscle proteins during gelation is believed to be an important structure building process that imparts strength to thermally-set gels. It is reasonable to speculate that crosslinking proteins in surimi processed mechanically deboned poultry meat would alter resulting texture. Washed mechanically deboned poultry meat can be considered a crude actomyosin complex that is reasonably free of sarcoplasmic proteins and lipids (Ball, 1988) which should provide an appropriate substrate for transglutaminase mediated cross linking reactions. This paper will present evidence for transglutaminase polymerization of crude actomyosin and report the results of early evaluations of the rheology of polymerized crude actomyosin.

Materials and Methods

Mechanically deboned turkey meat was supplied by Carolina Turkey, Mount Olive, NC. Transglutaminase (guinea pig liver) was obtained from Sigma Chemical Co., St. Louis, MO. Electrophoresis reagents and reagents for the Bradford assay were purchased from Bio-Rad Laboratories, Richmond, CA. All other chemicals were analytical reagent grade obtained from Fisher Scientific, Raleigh, NC.

90

The mechanically deboned turkey meat was washed and crude actomyosin was prepared as described by Akamittath et al. (1991). Details for the determination of polymerization using electrophoresis and change in free amino content were also described by Akamittath et al. (1991).

Polymerization of crude actomyosin was carried out in a total volume of 10 ml at pH 6 or 7 in 0.05M tris-maleate buffer, lOmM CaCl2, lOmM dithiothreiotol, 2 mg/ml crude actomyosin and 0.25 units transglutaminase. Incubation was at 4 or 37°C with 2 ml aliquot removed at 11, 21, and 26 hr or 10, 20, and 40 min, respectively. Cold EDTA (0.4 ml of 0.4M, pH 8.0) was added to terminate the reaction. Control non-polymerized samples were prepared by adding EDTA to the reaction mixture prior to adding enzyme. An additional control to detect proteolytic enzymes was prepared without enzyme or EDTA and incubated with the enzyme treated samples.

Polymerization of rheological samples was conducted at pH 6. Protein concentration was 14 mg/ml. Ionic strength was 0.55 with 20 1 of enzyme at 10 uglfA added.

The Bohlin rheometer was used to evaluate the rheological properties (Measuring system C 14; 1.757 g cm torque element; frequency of 0.05 Hz; amplitude of 14.4%; strain 0.02; heating rate of 0.5°C/min).

Results and Discussion

Incubation of crude actomyosin at 37 °C in the presents of transglutaminase resulted in a decrease in myosin monomer content with the simultaneous appearance of myosin polymers (PI, P2) (Figure 1). The myosin monomer content decreased about 60% at pH 6. Similar results were observed at pH 7 for samples incubated at 37°C. Polymerization also occurred at 4°C, but was much less. The incubated controls with and without enzyme did not show any loss of myosin monomer or increase in polymers indicating that electrophoretic changes were not due to contaminating proteolytic enzymes.

The percent of free amino groups exhibited simultaneous decrease as polymerization proceeded. A 30% decrease positively correlated (r2 = 0.99 for pH 7; r2 = 0.95 for pH 6) to the percent decrease in myosin monomer was observed.

Since the reaction mixture contained dithiothreiotol and electrophoresis was carried out under reducing conditions it is reasonable to expect that the proteins were dissociated into their constituent subunits. Since the polymers were detected under dissociating conditions in the presents of transglutaminase it is reasonable to conclude that the polymers were initiated by the enzyme.

91

The Theological thermogram of transglutaminase treated crude actomyosin is presented in Figure 2. The thermogram indicates gelation on heating from 25 to 76°C with an intermediate holding period of two hours at 37°C. Gelation appears to occur past 37°C with some increase in the storage modulus (G') during the holding period at 37°C (Figure 3). There was a rapid increase in G' at about 55 °C that continued to the end of the heating regime at 76°C (Figure 2). Maximum G' was not obtained until cooling to 25°C. At the onset of heating, the phase angle (d) is about 20° indicating a viscous sol. On heating to 37°C, including the two hour holding period (Figure 3), d decreased indicating a change from a viscous to an elastic behavior. It is interesting to note the minimum G' and maximum d at 48 - 50°C that probably are indicative of protein conformational changes. G' maxima for control crude actomyosin at the end of the heating and cooling were about 50% of the G' values obtained from the enzyme treated material (thermogram not shown).

The phase angle changes shown in Figure 3 indicate that the control crude actomyosin sample retained viscous behavior characteristics much longer than the enzyme treated material. The d-values for the treated materials suggest that the crude actomyosin become an elastic sol or perhaps a weak elastic gel due to polymerization.

The stress relaxation curves for crude actomyosin gels with and without enzyme treatment are shown in Figure 4. The relaxation time to achieve equilibrium stress was about the same for both samples. The extent of relaxation is however very different. The enzyme initiated polymerization imparts higher stress values indicating that the gels have very different internal network structure.

These results indicate that polymerization of crude actomyosin can be achieved with transglutaminase. The crosslinking action of the enzyme affords an opportunity to regulate the ultimate texture. Crosslinking can be achieved at temperatures as low as 4°C and it appears that much of the crosslinking that impacts on the ultimate G' is achieved at temperatures less than 50°C. The relationship of crosslinking and changes in low-strain rheology should be further explored to determine their impact on sensory properties and failure properties of gels made with the enzyme modified proteins.

References

Akamittath, J. G. and Ball, H. R., Jr. 1991. Transglutaminase mediated polymerization of crude actomyosin refined from mechanically deboned poultry meat. J. Muscle Foods (In press).

Ball, H. R., Jr. 1988. Binding and texture development in formed poultry meat products using mechanically deboned poultry meat refined by a "surimi-like" process. Final Report Southeastern Poultry & Egg Association, Decatur, GA.

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Dawson, P. D., Sheldon, B. W., and Ball, H. R., Jr. 1988. Extraction of lipid and pigment components from mechanically deboned chicken meat. J. Food Sei. 53: 1615-1617.

Dawson, P. D., Sheldon, B. W., and Ball, H. R., Jr. 1989. Pilot-plant washing procedure to remove fat and color components from mechanically deboned chicken meat. Poultry Sei. 68:749-753.

Dawson, P. D., Sheldon, B. W., and Ball, H. R., Jr. 1990. Effect of washing and adding spray-dried egg white to mechanically deboned chicken meat on the quality of cooked gels. Poultry Sei. 69:307-312.

Hernandez, A., Baker, R. C , and Hotchkiss, J. H. 1986. Extraction of pigments from mechanically deboned turkey meat. J. Food Sei. 51:865-872.

Kamath, G. G. 1990. Physico-chemical basis for the unique "setting" phenomenon of Alaska pollack and Atlantic croaker surimi. Ph. D. Thesis, North Carolina State University, Raleigh, NC.

93

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94

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97

98

CONDITIONS OF ISOLATION OF CHICKEN "SURIMI" FROM MECHANICALLY DEBONED MEAT AND ITS FREEZING

J. Kijowski, J. Stangierski and A. Niewiarowicz

Institute of Animal Products Technology, Agricultural University, 60-624 Poznan, Poland

Abstract

Conditions of myofibrils preparation from mechanically deboned chicken meat (MDCM) produced in a Lima separator were tested. Myofibrils (surimi) were obtained by a process of rinsing MDCM with tap water at 10° C followed by pressing it through the strainer (0.8 mm) for connective tissue separation and continual dewatering in Westfalia decanting centrifuge. Criteria for optimum conditions of surimi isolation were: protein and mass recovery as well as the degree of fat skimming from the preparation. Multiple washing with water, relation of MDCM to water, time of rinsing and additional grinding of MDCM in silent cutter, were optimized. The best results were achieved when MDCM was ground at 10 min. in silent cutter followed by 2-3 fold washing with water of 10°C, when MDCM to water ratio was 1:3 and rinsing time 15 min. It was found that freezing of surimi at -22°C and -60°C caused deterioration of its quality. Frozen surimi demonstrated significantly lower extractability of proteins as well as poorer texture parameters: hardness, springiness, and cohesiveness of the surimi gel.

Introduction

Production of mechanically deboned poultry meat (MDPM) is a well known common practice in the Polish poultry processing industry. According to our experience MDPM incorporated into poultry and meat products in higher amounts may cause quality deterioration in the final products. MDPM has high fat content, short storage life, dark color and small particle size of tissue fragments which results in poor textural properties. In the past there were some attempts towards improving the quality and functionality of MDPM. Application of centrifuging to MDPM reduced significantly fat content, cooking loss and improved emulsification capacity (Froning and Johnson, 1973).

99

Improvement of MDPM protein quality by enzymatic modification was examined by Smith and Brekke (1985). Young (1975) and Kijowski and Niewiarowicz (1985) proposed extraction of proteins from MDPM by using a salt extraction procedure to solubilize myofibrillar proteins. McCurdey et al. (1986) developed an alkaline extraction procedure on laboratory and pilot scale to solubilize protein from mechanically separated chicken residue. Acton (1973) showed that MDPM with low fat content could be texturized by heating. Megard et al. (1985) demonstrated that MDPM can be used for products formed by extrusion-cooking, when several non-meat ingredients were used. The Japanese developed a process to wash fish mince with water which results in a functional protein ingredient called "surimi". Surimi is actually a frozen concentrate of wet fish flesh myofibrils produced from water washed mechanically deboned fish muscle (Lee, 1984; Lanier, 1986). Rinsing of fish flesh removes fat, sarcoplasmic proteins, blood muscle pigment which are responsible for low storage stability. Mince is then squeezed to reduce the moisture, strained, mixed with salt, cryoprotectants and finely frozen. Surimi is a concentrated form of muscle actomyosin, and therefore the functional "essence" of meat. It is possible that functional protein can be recovered from lower quality source poultry meat as MDPM by application of surimi processing (Ball, 1988; Dawson et al., 1989; Kijowski, 1989). The high quality surimi from light muscles of fish species is white in color, odorless and tasteless. Surimi from fatty MDPM or dark fiber muscle system exhibits a greyish color, a slight flavor and must be specifically processed to yield a satisfying quality product. The objective of this research was the selection of optimum conditions of myofibrils (chicken-surimi) production from mechanically deboned chicken meat. The influence of freezing on quality of surimi was also investigated.

Materials and Methods

Mechanically deboned chicken meat (MDCM) was obtained from backs, necks and wings in a "Lima"-RM 500" separator. MDCM was frozen and stored at -18°C until use and thawed at 5-7°C.

MDCM washing procedure

Native MDCM or additionally comminuted MDCM in silent cutter (1400 rpm of knives) was washed with tap water at 10°C in a 35 dm3 volume agitator with constant speed of propeller. The slurry was then left undisturbed for 10 min and the fat was skimmed from the surface. The remaining mixture was pressed through the strainer (0.8 mm). The screening resulted in two fractions. One remaining on the strainer surface contained mainly connective tissue and the slurry was passing through the screen. The passing

100

fraction was partially dewatered in Westfalia-KDD-604 continual centrifuge at 6000 rpm. To get a higher yield of surimi preparation the fraction which remained on the strainer was again subjected to water washing, fat skimming and connective tissue removal. The criteria to obtain optimum conditions during grinding and washing were: mass (weight) yield, protein yield (recovery) and also the proximate composition with the stress on the lowest possible fat content. Based on the data for fish surimi production and our own experience the initial conditions were suggested: 10 minute of MDPM additional grinding, 3 fold water washing procedure for 15 min. each, MDPM to water ratio as 1:3. The conditions in these procedure were used as a reference. When one of the parameters was investigated the other remained unchanged. The following variable conditions of chicken-surimi production were tested: additional grinding of MDCM in a silent cutter, time of washing (rinsing), water to MDCM ratio during washing procedure and number of washing cycles. Moisture, protein (Kjeldahl), fat (Soxhlet) ash and collagen content (Arneth and Hamm, 1971) were determined in the samples of chicken-surimi. Protein extractability was determined in 0.1 M phosphate buffer, of pH 7.4 with addition of 1.1. M KJ according to Helander (1961) procedure. Expressible drip estimation was based on free water test (Hamm, 1968). Gels made from "chicken surimi" were prepared according to Kijowski (1989) by protein concentration of 14.5%. Texture analysis was performed according to Lyon et al. (1980) using Instron model 1140. From the two bite compression curves on each gel core (35 mm diameter, 10 mm thickness) hardness in Newtons, springiness and cohesiveness were calculated. The mean values and standard deviation for all determinations were calculated from 6 results obtained in 2 separate washings with 3 replications each.

Results

The proximate composition of MDCM which was used for surimi production is given in Table 1. The results of the grinding and washing procedures are given in Table 2-5. Results in Table 2 suggest that additional grinding of MDCM allowed to recover a greater amount of protein and simultaneously the fat removal process was easier. The 15 min. washing time gave the best yields of surimi but the increased number of washings evidently reduced the protein and mass yield of myofibrils recovery. From the data in Table 5 can be seen that single washing shows the best yield of mass and protein but the fat content remained high (about 1.2%). So, a second or third wash seems to be desirable in order to decrease the fat level in surimi. The higher water amount in the water: MDCM ratio during rinsing above 3:1 reduced the yield of myofibrils recovery.

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Finally the best conditions were achieved when MDCM was ground for 10 min. in the cutter followed by 2-3 fold washing in water at 10°C, when the water to MDCM ratio was as 3:1, and washing time 15 min. At conditions of isolation the proximate composition of surimi (myofibrils) preparation was: 89.2% water, 10.7% dry substance, 9.8% protein, 0.64% fat, 0.32% ash, and 0.66% collagen. Recovery of dry substance was about 32%, and of protein about 22%. Comparison of the results for the best surimi processing conditions to the proximate composition of the MDCM (Table 1) leads to the conclusion that the fat reduction in material was 21 fold. The reduction of ash content was about 3 fold. The recovery of the surimi (myofibrils) from the MDCM amounted to 32% of the raw material or 22% protein from the total protein of MDCM. Additional research is needed to improve yield in the chicken surimi isolation. However, it was a higher yield than that achieved for mechanically deboned meat from spent hens (Kijowski, 1989). In that study the average yield was 26.7% of raw material, whereas mass and protein recovery was about 19%. Those values were lower then those obtained for myofibrils recovered from breast muscle with a similar washing procedure, which was 56.4% of meat protein (Kijowski, 1989). Explanation of such a great difference in yield of myofibrils from different native material should be attributed to difference in chemical (protein) composition of the raw materials. Additionally it was found that freezing of surimi at -22°C and also at -60°C caused deterioration of the preparation quality. Frozen surimi showed significantly lower protein extractability, and higher free water content as well as the lower hardness of gel (Table 6). Lower temperature of freezing (-60°C) allows to secure better the protein extractability when compared to -22°C, but still extractability is still worse than that of the non frozen surimi. Wet myofibril concentrate freezed at -18°C all the rheological parameters (hardness, cohesiveness, springiness) turned out to be lower when compared to the fresh concentrate (Kijowski, 1989). The results suggest the necessity of cryoprotectant application when freezing of chicken myofibrils (surimi).

References

Acton, J.C., 1973. Composition and properties of extruded, texturized poultry meat. J. Food Sei. 38, 571.

Arneth, W. and Hamm, R., 1971. Untersuchungen zur Methodik der Hydroxyprolinbestimmung in Fleisch und Fleischwaren. Fleischwirt 51, 1523.

Ball, H.R., 1988. Surimi processing of MDPM. Broiler Industry 51 (6), 63. Dawson, P.L., Sheldon, B.W. and Ball, H.R., 1989. Pilot-plant washing procedure to

remove fat and color component from mechanically deboned chicken meat. Poultry Sei. 68, 749.

Froning, G.W. and Johnson, F., 1973. Improving the quality of mechanically deboned fowl meat by centrifugation. J. Food Sei. 38, 279.

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Hamm, R., 1986. Functional properties of the myofibrillar system and their measurements, In: Muscle as Food ed. by P.J. Bechtel. Academic Press Inc. Orlando Fl.

Heiander, E.A., 1961. Influence of exercise and restricted activity on the protein composition of skeletal muscle. Biochem. J. 78, 478.

Kijowski, J., 1989. Attemps at obtaining the wet concentrate of myofibrils from chicken breast and mechanically deboned poultry and its functional properties. Acta Alimentaria Polonica 15 (4), 317.

Kijowski, J. and Niewiarowicz, A., 1985. A method of protein extraction from chicken bone residue and the chemical and electrophoretic characteristic of the extract. J. Food Technol. 20, 43.

Lanier, T.C., 1986. Functional properties of surimi. Food Technol. 40 (3), 107. Lee, CM. , 1986. Surimi manufacturing and fabrication of surimi-based products. Food

Technol. 40 (3), 115. Lyon, CE. , Lyon, B.G., Davis, CE. and Townsend, W.E., 1980. Texture profile

analysis of patties made from mixed and flake - cut mechanically deboned poultry meat. Poultry Sei. 59, 69.

McCurdy, S.M., Jelen, P., Fedec, P. and Wood, D.F., 1986. Laboratory and pilot scale recovery of protein from mechanically separated chicken residue. J. Food Sei. 51, 742.

Megrad, D. Kitabake, N. and Cheftel, J.F., 1985. Continuous restructuring of mechanically deboned chicken meat by HTST extrusion-cooking. J. Food Sei. 50, 136.

Smith, D.M. and Brekke, C.J., 1985. Enzymatic modification of structure and functional properties of mechanically deboned fowl proteins. J. Agric. Food Chem. 33, 631.

Young, L.L., 1975. Aqueous extraction of protein isolate from mechanically deboned poultry meat. J. Food Sei. 40, 1115.

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Table 1 Proximate composition of MDCM (%).

Water Protein Fat Ash Collagen

70.2(0.24)* 14.2(0.26) 13.6(0.37) 1.1(0.05) 1.37 (0.06)

Mean value from n=6, between brackets standard deviation.

Table 2 Effect of grinding time of MDCM on the mass and protein yields and fat content of chicken surimi (%).

Grinding time (minutes) 5 10 15

Mass yield 24.0 (1.0) 25.5 (1.5) 32.0 (1.0) 32.5 (0.5) Protein yield 16.1(1.9) 16.3(2.7) 22.1(1.1) 21.8(1.6) Fat 2.14(0.06) 1.44(0.15) 0.64(0.06) 1.58(0.12)

Table 3 Effect of rinsing times of MDCM on the mass and protein yields and fat content of chicken surimi (%).

Rinsing time (minutes) 10 15 20

Mass yield Protein yield Fat

26.0 (4.0) 15.1 (0.7) 1.19(0.08)

32.5 (0.05) 19.8 (3.3) 0.88 (0.04)

32.0 (1.0) 22.1 (1.1) 0.64 (0.06)

22.5 (1.5) 16.5 (1.4) 0.65 (0.03)

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Table 4 Effect of water: MDCM ratio on the mass and protein yields and fat content of chicken surimi (%).

Water: MDCM ratio 2:1 3:1 4:1 5:1

Mass yield 26.5(3.5) 32.0(1.0) 31.5(2.5) 26.5(3.0) Protein yield 19.0(0.9) 22.2(1.1) 19.5(1.7) 17.9(1.6) Fat 1.06(0.11) 0.64(0.06) 0.60(0.02) 0.57(0.03)

Table 5 Effect of number of washings of MDCM on the mass and protein yield and fat content in chicken surimi (%).

Number of washings 2 3

Mass yield 46.5(1.5) 37.5(3.5) 32.0(1.0) 24.0(1.0) Protein yield 32.6(4.8) 25.3(5.0) 22.2(1.1) 15.0(1.9) Fat 1.29(0.09) 0.80(0.05) 0.64(0.06) 0.58(0.05)

Table 6 Effect of freezing on some properties of chicken surimi from MDCM (n=6).

Properties

Protein extractability (%) Free water (%) Hardness (N)* Springiness* Cohesiveness*

Before freezing

97. la

60.5a

50.6a

0.90a

0.88a

After freezing at -22°C

65.0C

71.3b

33.0b

0.83b

0.86a

at -60°C

78. lb

72.5b

31.5" 0.89a

0.89a

Means in rows with no common letters differ significantly at p=0.05 *of chicken surimi gels.

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106

PRODUCTION OF FURTHER PROCESSED POULTRY MEAT PRODUCTS AND ITS INGREDIENTS

J.M.J, van Deursen

Alfa-Laval Koppens, Postbox 11, 5640 AA Bakel, The Netherlands

Abstract

A description is given of the formulation system for further processed poultry products. Main problems are described.

Introduction

After years of explosive growth in sales of further processed poultry, the industry as well as the suppliers were forced to develop systems to control and guarantee constant parameters used during the production process. This results in a maximum quality product along with maximum yields. The standardization of a formulated formed product mix can be considered as the base of the whole process. The formulation system and it's related process technology for a convenience food product will be described. The main drawback in the past has been the excessive cooking time required by the consumer to cook to product from usually a flash fried, frozen state. Today the trend is, that more products require a fully cook, meaning the product's core temperature has to reach a minimum of 72°C before freezing.

Fully cooked products

There are three main reasons to require fully cook: 1. To eliminate possible traces of Salmonella, Listeria, etc. because the customer has no

guarantee to reach 72°C with preparing a flash fried frozen product.

2. When products are only flash fried and frozen at plant level, it might take the consumer upto 15 minutes cooking time to fully cook the product. Usually the product will be overcooked and will become dry and dark coloured.

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3. The product is often cooked at restaurant level in deep oil, which in turn means additional oil pick-up.

Flexible further processing line set-up

storage prebreaker grinder

vacuum mixer/C02

butter

— equilibration

c form batter bread flash fry oven freezing packing

further processing line

Material formulating

At all times the idea is to formulate a mix for a product which suits the market, depending on what segment and what price will be approached. This relates directly to the choice of the ingredients also behaviour towards processing starts here in the raw material.

Formula for nuggets (typical formulation)

breast meat thigh meat skin water salt phosphate soy isolate: supro 515 sugar

7o 55 24 9.0 9.0 0.8 0.4 1.3 0,5

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Formula preparation method

Grinder: - thigh meat plate 12 mm, - breast meat plate 18 mm or trimmings of about 30 to 60 mm, - skin plate 3 mm.

Mixer: ribbons: for formulated products such as nuggets, patties, etc. paddles: for marinated or whole boneless fillets, or trimmings, etc. for formed fillets. - add breast, thigh, salt and phosphate - mix 30 sec, - add water - mix 2 min, - add soy isolate - mix 2 min, - add skin - blend 3 min., during last minute add sugar, - addC02 to-2°C (or28°F), - blend under vacuum for 1-2 min. after adding C02, - empty mixer into 200 ltr. lift buckets and equilibrate for about 30 min. before forming.

Effect of ingredients

Salt a) adds flavour (pleasant up to 0,9%) b) restricts microbiol, growth c) interacts with meat proteins

1) - solubilises myofibrillar protein, - improves adhesion, binding on heating, - emulsifying agent for skin and fat, - improves water detention and so yield.

2) flavour: also check the salt level in the coating, batter and breading.

Phosphates (average upto 0,5%) Pyrophosphates and tripolyphosphates act in the presence of salt by increasing greatly the effect of the salt on the meat proteins. They increase cooking loss, yield, meat binding and texture and they accelerate the salt effects, allowing the same results to be obtained in shorter time.

Isolated soy proteins The isolated soy proteins provide the right degree of protein penetration to stabilize extra cellular water and possibly also diffuse into the meat membranes. The protein boosing effect of these isolated vegetable proteins, together with the salt and phosphates contributes significantly to the rapid absorption by the meat.

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co2 The mixing and massaging cyclus is completed, when by application of mechanical energy to the meat, to facilitate the extraction of the salt soluble myofibrillar proteins. After adding the skin, technically the mix is now ready for cooking. To guarantee proper forming characteristics, the mix needs to have enough body to maintain shape during the forming and coating process. For this reason carbon dioxide (C02) is widely used. It is injected in the vacuum mixer. A C02 nozzle which is usually positioned in the hood, injects C02 with a temperature of -75°C in snowform. The dry ice will extract the heat from the product. It is essential to have a perfect balance between the amount of C02, blending speed and time.

Possible problems inherent to a manual operation of the blending and C02 process

Ice crystal forming In case there is still free water present in the mix, there is an increased possibility of ice crystal formation. These ice crystals will damage the cells and connective tissue during the mechanical action. Also the mix will be unstable and will require more C02 and so be more expensive.

PLC controlled mixing process To obtain a continuous process one has to control the mixing process from the beginning to the end. Mainly because it is a batch process. Each batch should have a similar mix. Errors can be minimized by using a PLC controlled system.

Equilibration C02 cooled formulation requires an equilibration time between mixing and forming. The objective is to level-out the temperature differences. Usually about 30 minutes is used. The more uniform temperature the more uniform the stability of the formed product.

Balloon effect In case there is free water present in the mix, the mixing cyclus has not been completed, it results in steam forming during the cooking process, which has the following effects: - separation of the meat texture, balloon effect, - separation of coating from the product, - weight differences.

Infeed temperature Temperature differences in the mix entering the forming machine are directly related to the internal temperature differences of the fully cooked finished product.

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THE USE OF DAIRY INGREDIENTS IN FURTHER PROCESSED POULTRY PRODUCTS

H.A.M. Lemmers

DMV, De Melkindustrie Veghel bv, P.O. Box 13, 5460 BA Veghel, The Netherlands

Abstract

A dairy ingredient like sodium caseinate is a cost effective versatile functional ingredient in the production of high quality further processed poultry products. The addition of this ingredient provides options to meet technological issues such as improving product stability and eating characteristics, production efficiency and valorization of all constituent parts. Dairy ingredients can be applied in all subcategories of poultry products. The possible application techniques and typical functional characteristics needed of the added ingredients are to a large extent determined by the difference in degree of comminution. Research showed that sodium caseinate, apart from being an emulsifying protein, has a synergistic effect on the heat induced gelling of myofibrillar meat proteins.

Introduction

Further processing of poultry is the answer of the poultry industry to keep pace with the changing demographics, life styles and consumer preferences in which convenience, quality, healthy image and value for money play an important role (Wabeck, 1987).

Poultry consumption has increased significantly on a worldwide basis over the last five years. According to USDA data the total world poultry production in 1990 was around 32.6 million metric tons, representing a 24% increase in production volume compared with 1985. Further processed products and cut up parts account for an increased share of this production at the expense of whole birds.

Poultry processing is changing from a typical slaughtering operation to a further processing industry. Further processing of poultry can be defined as the conversion of raw carcasses into value added, more convenient to use forms (Baker and Bruce, 1989) and provides a market for under utilized parts of the carcass. Optimization of the so-called "poultry meat balance" is a major technological issue in production efficiency.

I l l

Consumers' preference for breast meat is forcing poultry processors to find ways to make use of raw materials such as thigh meat, mechanically deboned poultry meat (MDPM) and chicken fat/-skin in a range of further processed products. Improving product characteristics like consistency, binding, colour and taste, which determine to a large extent the perception of product quality is another important issue in the further processing concept.

This article describes, from a processor's point of view, which technological problems are encountered in further processing and the functionality and application technology of DMV dairy ingredients in order to produce high quality further processed poultry products on an economical basis.

Dairy ingredients

The two most important ingredients derived from milk which find application in processed poultry products are milk protein type sodium caseinate and milk sugar or lactose.

The functional properties of milk protein can be explained from its molecular structure. Due to the high proline and the low sulphur containing amino acids content milk proteins have a random coil structure with a low % helix. Sodium caseinate shows no heat gelation and denaturation and has a high viscosity in solution.

Sodium caseinate has a high electrical charge and has several very hydrophobic groups. This makes them perfect emulsifiers with a strong preference for the interface between fat and water in emulsified meat products. It is very well soluble in water, which is needed for optimal functional performance in poultry applications.

In processing of products like chicken rolls or turkey ham, salt and phosphates are used for optimal extraction of proteins from the meat muscle structure. The effective salt and phosphate concentration in water, and so the ionic strength, can be increased by increasing the total dry solids of the brine solution. For this purpose lactose is often used. Besides this lactose has advantageous effects on: * Taste: lactose has got the capacity of masking the bitter aftertaste of salts and

phosphates. Lactose itself has a low sweetness profile; therefore is does not induce undesired sweetness.

* Stability: lactose improves water binding, sliceability and enhances the cured colour. * Cooking yield.

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Problems encountered in further processing and application of dairy ingredients

Further processed poultry products can be categorized as:

1 finely comminuted: poultry frankfurters, -bolognas 2 coarsely comminuted: chicken burgers, -nuggets 3 non comminuted: breast of turkey, chicken roll

The possibilities of applying ingredients and typical functional characteristics needed of these ingredients are to large extent determined by the degree of comminution.

Finely comminuted poultry products

For a long time research on finely comminuted meat systems has been focused on emulsion theories (Schut, 1976). In recent years it was recognized that these theories oversimplify the composition of a multiphase comminuted meat system. Stability and consistency of comminuted products also largely depends on the nature of the continuous phase (matrix) which is basically a hydrophilic colloidal aqueous solution of salt and proteins (Asghar et al., 1985).

Valorization of raw materials like skin and fat, mechanically deboned poultry meat (MDPM) and thigh meat, by incorporating them in products like poultry frankfurters and -bolognas, is common practice in further processing of poultry. Addition of functional dairy ingredients is necessary in maintaining acceptable standards for consistency, stability, eating characteristics and appearance.

Sodium caseinate is first of all an emulsifying protein, which is preferentially adsorbed at the fat/water interface over myofibrillar meat proteins. Because of this, myofibrillar proteins are saved from interfacial denaturation and subsequent loss of gelling capacity. Therefore, the myofibrillar proteins can perform maximum gelling capacity upon heating and provide product stability. In this way added milk protein contributes directly to a better fat binding through emulsification and indirectly to an improved water binding and texture formation (see also paragraph 3).

Mechanically deboned poultry meat (MDPM), being a cost effective raw material, is widely used in finely comminuted poultry products. Technologically speaking, the largest limitations in the use of MDPM are its negative taste and colour and the partial or even total absence of muscle structure. Water and fat holding capacity is low and above all, because of the lack of meat fibres, the product remains relatively soft. In finely comminuted poultry products, where large amounts of MDPM

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are incorporated, the use of milk protein sodium caseinate is recommended. An ingredient which is not only effective in stabilizing fat and water, but it also lightens the colour imparted by the addition of MDPM and gives the final product consistency and improved taste.

An example of such an industrial product formulation, using a substantial amount of MDPM could be the following application suggestion, prepared with sodium caseinate. The influence of different application techniques of sodium caseinate on stability and consistency as well as on product properties like colour and appearance was investigated.

Recipe A Poultry Bologna

Thigh meat M.D.P.M. Salt Polyphosphates Water/ice Sodium caseinate EM 6 Chicken skin/-fat mixture Spices

10.0 % 49.1 % 2.0 % 0.3 %

16.0 % 2.0 %

20.0 % 0.6 %

Variations

I

II III

reference, no milk protein addition EM 6, dry addition EM 6 with water and skin/-fat in a (1:5:5:6+2) pre-emulsion (see par. 2.2)

100.0 %

Evaluation

* Cooking loss/separation: I: 5.7%, II: 1.3%, III: 0.7% * Addition of sodium caseinate results in:

- attractive light colour - improved stability - better consistency and eating characteristics.

The results are more pronounced, when the pre-emulsion concept is applied.

Chicken skin/-fat pre-emulsions

Incorporation of chicken skin and fat in large quantities as such in finely comminuted or coarsely comminuted products may lead to a number of technological and organoleptic problems.

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Problems which can arise are: - poor stabilization of the fat because immediate release from its cell structures takes

place when only limited mechanical action is applied. Due to its structural properties poultry fat is difficult to stabilize in processed products; abdominal chicken fat is built up by large cells surrounded by thin cell walls.

- negative textural changes upon heating (e.g. shrinkage). - possible occurrence of off-flavours and soft consistency of the fat influenced by feeding

regimes.

To overcome these problems the concept of a pre-emulsion can be applied, in which chicken skin and -fat are pre-stabilized by means of addition of highly functional sodium caseinate. Furthermore the incorporation of these pre-emulsions in product formulations leads to improved organoleptic properties (succulence, consistency).

Table 1 summarizes the most important characteristics of two different pre-emulsion procedures being a so-called "cold preparation-" and a "hot preparation method".

Table 1 Characteristics of two typical pre-emulsions.

Ratio Method Use in Remark

l:5:5:(6+2)*

l:8:8:(4+4)**

Cold preparation

Hot preparation

Coarsely comminuted restructured products, like burgers and nuggets Finely comminuted products

Finely comminuted products

Improvement microbio­logical status

* Consists of 1 part milk protein, 10 parts of raw chicken skin and fat (5 + 5) mixture, 6 parts of water and 2 parts of ice.

** Consists of 1 part milk protein, 16 parts of pre-cooked chicken skin and fat (8 + 8) mixture, 4 parts of water and 4 parts of ice.

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By means of comminuting equipment used in the processing industry and addition of milk protein, chicken skin/-fat is effectively comminuted and incorporated by applying this pre-stabilization concept. Microscopic examination has confirmed this as shown in Figure 1, which is a picture of a l:5:5:(6+2) pre-emulsion prepared with sodium caseinate. This picture has been made with bright field illumination, magnification 700 x. The average particle size is approximately 2 /*m and size distribution is rather narrow. The high emulsifying capacity of milk protein is needed in this concept because it is capable of forming a so-called "true emulsion" in which each fat particle is surrounded by a thin layer of milk protein.

Coarsely comminuted poultry products

Products like chicken burgers and chicken nuggets are produced in a restructuring process which is basically a process of transforming various parts, cuts and trimmings into new structured forms. This technology allows the upgrading of lower grade raw materials to produce high quality products. To a large degree the restructuring process depends on the heat-induced binding that takes place between the meat pieces, and which is related to the presence of an exudate of salt-extracted proteins (mainly myosin) at the meat particle interface.

Fat- and moisture release during heating of restructured products often results in dry eating characteristics, shrinkage and of course lower yield values. It is generally recognized that processed poultry products need to contain a certain quantity of fat and moisture to give an acceptable mouthfeel (succulence) and flavour. The concept of adding a chicken skin/-fat pre-emulsion has proven to be a good option to meet this demand. Incorporation levels can be up to 20-25%, depending on specific type of formulation.

Summarizing, the advantages of skin-/fat addition in the form of a cold prepared pre-emulsion in these types of products are: - better valorization of these by-products because level of fat-/skin addition as such is

limited in these products. - option for cost effective recipe extension. - improved eating characteristics (juiciness, taste). - higher yield compared with separate addition of the raw materials.

Stability improvement expressed as cooking yield was investigated in the following product formulation.

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Recipe B Chicken burger

Chicken breast meat Chicken thigh meat Polyphosphates Milk protein sodium caseinate EM 6 Salt Water l:5:5:(6+2) pre-emulsion * Pepper Onion powder

20.0 55.3 0.3 0.3 0.8 5.5

17.5 0.1 0.2

100.0 * prepared with sodium caseinate EM 6

The influence of the method of incorporating increasing levels of water and chicken fat/-skin on the yield after heating was investigated. This was carried out with deep frozen products on a hot plate (200°C) for 10 minutes. Addition of a 1:5:5:(6+2) pre-emulsion was compared with separate addition of its individual components including the milk protein. Increased emulsion addition was compensated by decreasing amount of dark chicken thigh meat. The results are presented in Figure 2.

Adding chicken skin/-fat in form of a pre-emulsion results in better stability, higher yield and subsequently improved eating characteristics. Increasing the amount of pre-emulsion incorporation lowers the cooking yield because of loss of binding capacity of the thigh meat, which is reduced. But the pre-emulsion concept always results in an improved stability in comparison with separate addition.

Non comminuted poultry products

One of the most popular products in this group of whole muscle poultry products is breast of turkey. Yield, colour, consistency, binding and taste are the most important product characteristics. These are greatly influenced by the type of added non meat protein or other ingredients like starches and thickeners. A dairy derivative like milk protein sodium caseinate has the advantage of combining stability- and consistency improvement with a bland flavour profile and low impact on the original product characteristics. This is demonstrated by Table 2: results of application trials with a 30% (on weight) injected cooked breast of turkey.

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Table 2 Influence of added sodium caseinate in brine on product characteristics of Breast of Turkey.

Brine ingredients

Water Polyphosphates Salt Lactose Sodium caseinate EM 6

% in final A

19,6 0,3 1,3 0,4

product B

19,6 0,3 1,3 0,4 1,5

Cooking yield A B

107,4% 115,1%

Sensoric evaluation A dry texture,

poor sliceability B juicy, improved

sliceability and consistency, no difference in taste

Influence of added non meat proteins on myosin gelation

In order to establish a confirmation of the experienced positive functional role of milk proteins type sodium caseinate during the heat induced myosin gelation, a research was carried out to investigate the interaction between milk protein and meat proteins. To study this effect we have to make a classification of proteins present in meat. Meat protein can be divided in different groups according to their specific function and solubility in different solvents (see Table 3).

Table 3

Classification of meat proteins

Protein

Sarcoplasmic Stromal Myofibrillar

%

30-35 15-20 50-55

Function

metabolic connective contractile

Solubility

water insoluble salt. sol.

Gellifying properties

weak no strong

Emulsifying properties

weak weak strong

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Myosin from different meat muscle sources can differ in heat induced gelling characteristics under similar ionic concentration, pH value and protein content (Asghar et al., 1985). It is evident however, that the presence of sufficient salt soluble myofibrillar proteins, myosin in particular, is a prerequisite for formulation of a firm visco-elastic gel matrix upon heating (Foegeding and Lanier, 1989). In our experiments lean meat (M. Semimembranosis) was extracted according the following extraction procedure; 63% lean meat is finely comminuted with addition of 2% salt and 35% ice/water in the bowl chopper. After dilution with 200% brine (2% salt level) the lean meat slurry is centrifuged.

After centrifugation there are three distinct layers in the centrifuge tube; the upper layer contains the water soluble- or sarcoplasmic proteins (WSP) and the salt soluble myofibrillar proteins (SSP).

The gellification of WSP/SSP proteins was examined in the following solution: * 3% SSP/WSP proteins * 3% NaCl * 2% milk protein The equipment for these tests was the Gelograph (Gel Instrumente AG, Rüschlikon), which measuring unit is based on the following principle: a protein solution which is placed in a waterbath is slowly heated (l°C/min.). During this heat treatment the viscosity/gel strength of the protein solution is continuously monitored by means of an electrically agitated oscillating needle, which operates in a non destructive way. The needle produces a minimal oscillation and at the same time generates an indication voltage proportional to the alteration in the structure of the gel. The gel structure which is formed during the heating of the solution is not destroyed because of minimal oscillating of the needle. In this way the gelling of meat proteins in meat products during heating processes is imitated.

Results of Gelograph experiments are presented in Figure 3 and 4.

This Figure shows the gel strength of a 3% WSP/SSP solution as function of time and temperature. The temperature starts at 20°C (= 68°F) and is increased at a rate of l°C/min.; during this temperature increase, the gel strength is measured in milligels, which is a gelograph specific unity. At 44°C there is a sudden increase in gel strength; this is the so-called first transition temperature of myosin caused by the aggregation of myosin molecules. On going in temperature rise the viscosity decreases again. The reason for this phenomenon is not yet exactly known.

At a temperature of 57°C there is again an increase in gel strength. With further heating of the solution to 75°C the gel strength reaches a constant value of + 150 m gels. Cooling down the solution results in a final gel strength of + 200 m gels.

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The same experiments were carried out with addition of 2% of two different types of dairy ingredients; milk protein sodium caseinate and a product composed of milk protein, lactose and milk minerals. This in comparison with 2% of a commercially available soy protein isolate.

Addition of 2% milk protein (which has no gellifying capacity itself) results in a much higher gel strength of a heated meat protein solution. Soy protein isolate (SPI), although a gelling protein itself, has this specific function only to a limited extent. This result supports the theory that there is a synergistic effect of milk protein on the gellifying capacity of salt soluble meat proteins, probably by absorbing a significant amount of water. This results in a higher net concentration of myosin molecules giving increased gel strength.

References

Asghar, A. et al., 1985. Functionality of muscle protein in gelation mechanisms of structured meat products. CRC Critical Reviews in Food Science and Nutrition, No. 1 (22), p. 27-106.

Baker, R.C. and Bruce, C.A., 1989. Further processing of poultry. In: Processing of poultry. Mead G.C. (ed), Elsevier Science Publishers Ltd.

Foegeding, E.A. and Lanier, T.C., 1989. The contribution of non muscle proteins to texture of gelled muscle protein foods. In: Protein quality and the effect of processing. Marcel Dekker Inc., New York.

Schut, J., 1976. Meat Emulsions. In: Food Emulsions. Friberg. S. (Ed.), Marcel Dekker Inc., New York.

Wabeck, C.J., 1987. The future of broiler processing. Broiler Industry, March, p. 34-42.

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Figure 1 Microscopic picture (magn. 700x) of a 1:5:5:(6+2) chicken skin/-fat pre-emulsion based on sodium caseinate.

«

100

90

80

70

60

50

40

A. separate addition B. pre emulsion

1:S:5K6*2)

0 4 8 12 16

addition (% on total)

Figure 2 The effect of processing method of fat/skin on yield.

20

121

Gelograph meat protein no addition

1000

100

60 90

time (min)

Figure 3 Gelograph of meat protein, with no additions

Gelograph meat protein no addition, caseinate, EMSER, SPI

1000

3 E

100 :

Figure 4 Gelograph meat protein. A - no addition; B - SPI; C - milk protein product EMSER 736; D - sodium caseinate EM6

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MODIFICATION OF MYOFIBRILLAR PROTEINS EM SPENT HEN MEAT WITH PHOSPHATES IN THE PRESENCE OF SODIUM CHLORIDE

J. Kijowski

Institute of Animal Products Technology, Agricultural University, 60-624 Poznan, Poland

Abstract

Sodium diphosphate or triphosphate in amounts of 0.25-1.0% were added to mixtures of ground and salted with 2.5% ofNaCl breast and thigh of spent layers for 18 hr at 4°C. As a result, increases in the solubility of actomyosin and dissociation of this complex were achieved. The extractable actomyosin and myosin amounted to more than 1/4-1/3 of the content of all this protein complex in the meat. The application of 0.25% diphosphate or triphosphate resulted in a considerable downward shift, about 2.0 pH units, of the isoelectric point of meat proteins, but only in the presence of 2.5% NaCl. Since phosphates, especially sodium triphosphate cause analogous changes of the isoelectric point to ATP, addition of phosphates seems to be the simulation of pre rigor conditions in muscle. The most efficient in reduction of thermal drip in the meat and increasing of gelling capacity of meat proteins appeared to be the application of'0.25'% diphosphate addition.

Introduction

In the processing of poultry meat, sodium triphosphate (TPP) alone or blended with other phosphates is the most widely used phosphate. From the Oord and Wesdorp (1978) study it is known that TPP is effective after enzymatic hydrolysis to diphosphate (PP) and that its structure is analogous to ATP. After the addition of 0.5% TPP to meat, it is broken down after only 9-19 minutes of blending (Neraal and Hamm, 1977). The simultaneous addition of NaCl and phosphate to the meat causes considerable modifications of physicochemical features of myofibrillar proteins. But the combined effect of NaCl and phosphate in meat is not clearly understood in spite of many intensive studies in this field (Foxetal., 1982).

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The objective of this study was to evaluate the addition of pyrophosphate (diphosphate) (PP) and triphosphate (TPP) from 0 to 1 % to the minced meat upon: 1. the solubility (extractability) of the actomyosin complex (AM) and its dissociation in

2.5% NaCl solution. 2. the value of the isoelectric point (IP) of meat proteins. 3. the gelling capacity of meat proteins and thermal drip after cooking of meat.

Materials and Methods

Breast and thigh muscles of spent hens were reduced in size by passing through a meat grinder (2 mm diameter holes in plate). Sodium chloride (2.5% by weight) and either sodium diphosphate Na4P207 or triphosphate Na5P307 were initially dissolved in water of 40°C and then added to the meat samples in the amount equal to 10% of weight of the samples.

Solubility of actomyosin (AM) and myosin (M) as products of actomyosin dissociation was investigated in meat samples with 2.5% NaCl and 0.0; 0.25; 0.5; 0.75 and 1% of PP or TPP. Actomyosin and unbound myosin were isolated from protein solutions by dialysis according to a modified method of Sayre (1968) described by Kijowski (1984), and than purified with 1% triton xlOO.

Determination of isoelectric point (IP) values after NaCl, Na2ATP, PP and TPP addition was based on drawn curves of meat hydration in samples by adjusting pH value with 0.1 M HCl. The curves of meat hydration were estimated using the method of free water analysis according to Hamm (1972). The least amount of water was bound by the meat system at the isoelectric point.

Gelling capacity of meat proteins was evaluated with the least concentration endpoint method according to modified methods of Trautman (1966) and described by Kijowski and Niewiarowicz (1978).

Thermal drip was determined as the percentage of homogenate meat with NaCl solution after heating 30 min. in 70°C according to the method described by Zabielski et al. (1984).

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Results

The addition of diphosphate and triphosphate to the ground meat significantly increased the solubility of actomyosin and unbound myosin in 2.5% NaCl solutions proportional to the quantity of additives (Figure 1). Decrease of extractable actomyosin (AM) and the increase of myosin (M) was similar for PP and TPP, and amounted to 7.2-10.7% for AM and 4.6-11.7% of total nitrogen for M. It amounts to not more than 1/4-1/3 of the total content of these proteins in the meat. The most effective phosphate in dissociation of the AM complex was TPP. Correlation coefficients of myofibrillar protein solubility and technological properties after heating were significantly high (P<0.01; Table 1).

Table 1 Correlation coefficients of myofibrillar protein solubility and technological properties after heating (n=12).

Thermal drip Gelling capacity PP TPP PP TPP

Actomyosin -0.89 -0.93 -0.88 -0.96 Myosin -0.80 -0.85 -0.98 -0.97

Correlation coefficients for myosin are not greater than for actomyosin. This confirms that dissociation of AM is not decisive for particularly high functionality of phosphate.

Since determination of extractability and dissociation of AM gave unsatisfactory information about the phosphate mode of action in meat, the determination of changes of the isoelectric point of meat proteins was carried out. The addition of 2.5% NaCl to the comminuted hen meat significantly shifted-down the IP of meat from pH 5.4 to pH 4.3 (Figure 2a). The addition of 4.0% NaCl is more effective and the IP value of meat was 3.4. Additives of 0.25% and 0.5% PP, TPP or ATP only slightly lowered the pH of the IP of meat proteins (Figure 2b and Figure 3a,b). But in the presence of NaCl all these additives significantly decreased the IP of proteins to the pH value of 3.6-3.1, it means shifting-down of about 2.0 pH units. Increases of PP, TPP, ATP concentrations only slightly shifted the pH of IP of hen meat. This efficient method of shifting-down the pH value of meat protein isoelectric points by PP and TPP with the synergistic action of Na+, Cl"-ions provides a newer way of explaining of the mode of action of these substances. Changing the value of the IP by about 2.0 units causes the increase of negative electrostatic charge of myofibrillar proteins. This occurs in the range of typical pH values for aging hen meat (5.7-5.9). It is

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worth to note, that shifting of IP is the most effective with 0.25% PP or TPP concentrations. The same concentration is efficient in reducing thermal drip from meat homogenate. Sodium triphosphate or a mixture of phosphates could be successfully replaced by sodium diphosphate. Since PP and especially TPP causes analogous changes of the isoelectric point to ATP, addition of phosphate seems to simulate the pre rigor conditions in muscle.

References

Fox, P.F., Morrisey, P.A. and Mulvihill, D.M., 1982. Chemical and enzymatic modification of food proteins. In Developments in Food Proteins - 1 ed. by Hudson, B.J.A. Applied Science Publishers, London.

Hamm, R., 1972. Koloidchemie des Fleisches. P. Parey Verlag, Berlin. Kijowski, J. and Niewiarowicz, A., 1978. Effect of initial pH in broiler breast muscles on

gel forming capacity of meat proteins and rheological characteristics of frankfurter-type sausage. J. Food Technology 13, 461.

Kijowski, J., 1984. Characteristics of myofibrillar proteins in the breast muscles of broilers and hens during post mortem aging of meat. Fleischwirtschaft 64, 822.

Neraal, R. and Hamm, R., 1977. Über den enzymatische Abbau von Tripolyphosphat und Diphosphat in Zerkleinertem Fleisch II. 2. Lebensmittel Untersuchung und Forschung, 163.

Oord, A.H. and Wesdorp, J.J., 1978. The specific effect of phyrophosphate on protein solubility of meat. Proc. 26th Meat Researcher Congress, Kulmbach (W. Germany.

Sayre, R.N., 1978. Post-mortem changes in extractability of myofibrillar protein from chicken pectoralis. J. Food Science 33, 609.

Trautman, J.C., 1966. Effect of temperature and pH on the soluble protein of ham. J. Food Science 37, 409.

Zabielski, J., Kijowski, J., Fiszer, W. and Niewiarowicz, A., 1984. The effect of irradiation on technological properties and protein solubility of broiler chicken meat. J. Food Science and Agriculture 35, 662.

126

%MP

LSD(0,05)=16

LSD(0,05)48

0,0 0,25 0,50 0,75 1,0 %PP,TPP Figure 1 Effect of sodium diphosphate (PP) and sodium triphosphate (TPP) addition on

actomyosin (AM) and unbound myosin (M) distribution in myofibrillar protein (MP) extracted by 2.5% NaCl solution. LSD - least significant difference.

127

a: UU i— < 3: o z. O as 0 s

90

80

70

60

50

40

30

90

80

70

60

50

40

30

x2,5%NaCl 0%NaCl

®

0,25% ATP

2,5 %NaCl+ 0,25% ATP

2,5%NaCl+0,5%ATP ®

- < l — i H

2 3 4 5 6 7 pH

Figure 2 Influence of NaCl (a) and ATP (b) addition on hydratation plots of hen meat proteins. On the axis of abscisae the values of isoionic points are marked.

128

90

80 H

70

60 \

50

40

ce 30 LU J w

90 o

S 8 0

CO

^ 70

60

50

40

30

5%NQCI+0,25%PP

.25% PP

|,5% PP

-H "-

*• v / 2 , 5 % N Q C I + 0,5%PP

x y

J_L

®

0,25%TPP

2,5%NQCL

+0,25%TPP/ /

\ \ / / \ V * 2.5%NaCt + 0.5%TF»P

®

3 4 5 6 7 PH

Figure 3 Influence of sodium diphosphate (PP) (a) and sodium triphosphate (TPP) (b) addition on hydratation plots on hen meat proteins. On the axis of abscisae the values of isoelectric points are marked.

129

YIELD, QUALITY AND TEXTURE OF "SUREVH" WITH OR WITHOUT CONNECTIVE TISSUE OF CHICKEN AND SPENT HEN MECHANICALLY DEBONED MEAT

J. Kijowski, A. Niewiarowicz and J. Pikul

Institute of Animal Products Technology, Agricultural University, 60-624 Poznan, Poland

Abstract

Quality of "surimi " preparation and texture of surimi gels, produced from mechanically deboned meat (MDM) from chicken and hen were compared. MDM was rinsed with tap water at 10° C and separation of connective tissue followed. Recovery of myofibrils preparation after separation of connective tissue on the strainer was 2 times lower than that without that separation. Collagen content in surimi without and with connective tissue was 0.7-0.8% and 27-30% respectively. The colour of surimi containing connective tissue was characterized by higher "L "-value and lower "a "-value. The greatest hardness exhibited surimi gel free of connective tissue produced from spent hen MDM. Surimi gels without connective tissue demonstrated direct relationship between hardness and protein concentration. Surimi gels which contained connective tissue demonstrated significant thermal shrinkage and non-homogenous structure. Surimi preparation from MDM of spent layers demonstrated higher protein yield and stronger texture of gels than those obtained from MDM of broilers

Introduction

Surimi is traditionally defined as a bland, colourless, refined fish muscle protein prepared by washing the mechanically deboned fish meat (Lanier, 1986). Some research has been done to examine the suitability of utilizing mechanically deboned meat (MDM) from different poultry species and carcass parts in the manufacture of surimi-like preparation. Water but also other washing solutions as sodium bicarbonate, acetate buffer, phosphate buffer were tested (Hernandez et al., 1986; Dawson et al., 1988; Lin and Chen, 1989; Kijowski, 1989). MDM from poultry is much worse raw material for high quality surimi than the fish flesh. Poultry MDM contains much more fat, pigment, connective tissue, therefore the resulted surimi-like product after washing procedure is not very similar to

131

fish surimi. The poultry MDM contains a great amount of connective tissue which is dependent on type of deboner and on carcass part deboned. The high collagen content in poultry surimi-like products could be a problem in its utilization for new or traditional finished products. The objective of this study was the examination of yield and some quality characteristics of surimi-like product with or without connective tissue obtained from chicken and spent hen mechanically deboned meat.

Materials and Methods

Mechanically deboned meat (MDM) from spent hens whole carcasses and from broiler backs, necks and wings was supplied by a commercial processing plant. The mechanical deboning was carried out using Lima RM-500 (France) deboner. MDM was frozen and stored at -18°C until use and thawed at 4-6°C. MDM washing procedure was as follows: One part of MDM was washed with 4 parts of tap water (10°C) in a 35 dm3 volume agitator with constant speed propeller. The mixture was left for 10 minutes and fat was skimmed from the surface. The mixture was then centrifuged at 2.300 g in K 26 Janetzki centrifuge for 20 min at 4°C. The dewatered slurry with connective tissue was rewashed with water 3 times more and centrifuged in the some way. From the other samples of the washed and centrifuged MDM, the connective tissue was separated by pressing the material through the strainer (1.5 mm openings diameter). The passing fraction was dewatered with Janetzki K 24 centrifuge at 7000 g. The deposit containing mainly myofibrils was called "poultry surimi". After centrifugation the residue was weighed and compared with he initial weight to calculate yield. In samples of MDM and poultry surimi the moisture, protein (Kjeldahl), fat (Soxhlet) and collagen content (Arneth and Hamm, 1971) were determined. Free water was determined according to Hamm method (1986). The pH assay were based on Japanese grading system of fish surimi (Nippon Suisan Kaisha Ltd, 1980). Colour measurements were made with Gardner colormeter, USA. The calculation of x, y, z value of Hunter colour parameters was accomplished according to instruction of Clydesdale (1984). Lightness (L) and chromaticity dimensions "a" (redness) and "b" (yelowness) were calculated. The gels were produced using 100-300 g of "poultry surimi" blended intensely with NaCl for 10 min. The resulting paste was stuffed into 21 mm diameter collagen casing divided into 120 mm length segments (50 g sample) and heated in a water bath at 70°C for 40 min. Samples were then cooled in tap water, casing removed and cylindrical specimens (10 mm high) were sliced and then exposed to the texture profile analysis according to Lyon et al. (1980) using Instron model 1140. From the two bite compression curves on each gel (21 mm diameter) hardness (Newtons), springiness and cohesiveness was calculated.

132

The relations between hardness of chicken surimi gels with or without connective tissue and protein concentration were established and respective curves drawn. All determinations were done in three replications and standard deviations (in parenthesis) calculated).

Results

The proximate composition of the mechanically deboned meat (MDM) from broilers and spent hen is given in Table 1. MDM from hen whole carcasses seems to be a better raw material for surimi production because it contains 3.0% more protein and 3.5% less fat at the same level of dry substance. The proximate composition of surimi preparation with and without connective tissue is given in Table 2. Removal of connective tissue influenced the proximate composition of surimi preparation. Surimi from broilers without connective tissue contained less dry substance and less fat, but more protein then the controls with the connective tissue. In contrast, surimi from hens contained more fat after connective tissue separation. Surimi from spent hens was richer in protein then that from chicken. The connective tissue separation diminished almost twice the yield of surimi preparation, from 70.3% for broilers and more then twice (from 82.7% to 40.7%) for hens (Table 3). Even more declined the yield of protein recovery (Nx6.25) after connective tissue separation (Table 4). In the surimi from broilers the level of recovered protein was reduced from 76.7% to 26.8% and in surimi from hens reduction of protein amounted to 42.6% (from 74.4% to 31.8%). Such high losses of mass and protein raise the question of profitability of connective tissue separation from poultry surimi. But the homogeneity and general quality of myofibrils preparation without connective tissue fragments is higher when the collagen-rich fraction is separated. Protein loss after rinsing MDM with water contained mainly sarcoplasmic proteins in mounts of 23 to 25% in surimi with connective tissue and 33-35% when chicken and hen surimi contained connective tissue fraction (Table 4). The other characteristics of surimi with and without of connective tissue are given in Table 5. Collagen content in relation to total protein, was as 27-30%, and after separation of connective tissue, only 0.7-0.9%, in surimi from broilers and hens, respectively. Free water determinations indicated no differences between surimi with and without connective tissue and between surimi preparations from broilers and hens. As it was expected the colour of surimi with connective tissue was lighter when compared to connective tissue free surimi and L-value was greater for both broiler and hen surimi. Broiler and hen surimi without connective tissue was more red (14.1 and 6.6) than that with connective tissue (8.0 and 3.8). The colour of chicken and hen surimi is not white or pink but rather light beige. Connective tissue-free surimi was more yellow than the other one. Gels obtained after cooking of surimi paste from which the connective tissue was not removed exhibited non-homogenous structure and thermal shrinkage. The 21 mm diameter of gel after cooking in 70°C become smaller by 4 mm.

133

The hardness of the gels made of hen surimi was greater than that of chicken. The gels with low collagen content indicated direct relation between hardness and protein concentration (Figure 1). High collagen gel showed lower dynamics of hardness increase in the case of lower protein concentration but higher dynamics in the case of higher protein concentration in gel. Cohesiveness and springiness of all investigated gels were similar.

References

Arneth, W. and Hamm, R., 1971. Untersuchungen zur Methodik der Hydroxyprolinbestimmung in Fleisch und Fleischwaren. Fleischwirtschaft 51 (10), 1523.

Clydesdale, F.M., 1984. Color measurements. In: Food Analysis, Ed. by D.W. Gruenwedel and J.R. Whitaker, Marcel Dekker Inc., New York.

Dawson, P.L, Sheldon, B.W. and Ball, H.R., 1988. Extraction of lipid and pigment components from mechanically deboned chicken meat. J. Food Sei., 53 (6), 1615.

Hamm, R., 1986. In: Muscle as Food, Ed. by P.J. Bechtel Academia Press Inc., p. 135. Hernandez, A., Baker, R.C. and Hotchkiss, J.M., 1986. Extraction of pigments from

mechanically deboned turkey meat. J. Food Sei., 51 (4), 865. Kijowski, J., 1989. Attemps at obtaining the wet concentrate of myofibrils from chicken

breast and mechanically deboned poultry and its functional properties. Acta Alim. Polonica 15 (4), 317.

Lanier, T.C., 1986. Functional properties of surimi. Food Technol., 40 (3), 107. Lyon, CE. , Lyon, B.G., Davis, CE. and Townsend, W.E., 1980. Texture profile

analysis of patties made from mixed and flake-cut mechanically deboned poultry meat. Poultry Sei. 59 (1), 69.

Lin, S.W. and Chen, T .C, 1989. Yields, color and compositions of washed, kneaded and heated mechanically deboned poultry meat. J. Food Sei. 54, 561.

Nippon Suisan Kaisha Ltd, 1980. Standard procedure for quality evaluation of frozen surimi. Tokyo.

134

Table 1 Proximate composition of MDM (%).

MDM Water Dry subst. Protein Fat

Broilers 69.4(0.27)* 30.6(0.27) 15.1(0.26) 15.2(0.23) Spent hens 69.3(0.91) 30.7(0.91) 18.0(0.11) 11.8(0.33)

*in parenthesis standard deviation.

Table 2 Proximate composition of surimi preparation with and without connective tissue produced from broiler or spent hen MDM (%).

With connective tissue Without connective tissue Broilers Hens Broilers Hens

Water 81.9(0.41) 80.4(0.57) 82.6(0.36) 80.7(0.90) Dry subst. 18.1(0.70) 19.6(0.57) 17.4(0.36) 19.3(0.90) Protein 13.4(0.21) 16.2(0.26) 15.3(0.15) 16.7(0.23) Fat 3.1(0.25) 0.69(0.19) 1.2(0.18) 1.7(0.25)

Table 3 Influence of connective tissue separation on the yield of mass balance in surimi preparation from broiler and spent hen MDM (%).

With connective tissue Withhout connective tissue Broilers Hens Broilers Hens

Surimi (myofibrils) 70.3(0.17) 82.7(0.21) 37.3(0.06) 40.7(0.37)

Connective tissue fraction - - 18.4 (0.07) 21.8 (2.67)

Weight loss 29.7(0.31) 17.3(0.21) 44.3(0.00) 37.9(2.83)

135

Table 4 Influence of connective tissue separation on the yield of protein balance in surimi preparation from broiler and spent hen MDM (%).

With connective tissue Broilers Hens

Without connective tissue Broilers Hens

Surimi (myofibrils)

Connective tissue fraction

Protein loss

76.7 (1.49) 74.4 (1.09)

23.3(0.15) 25.6(0.09)

26.8 (0.39)

37.6 (0.01) 35.5 (2.67)

31.8 (2.93)

34.7 (5.82) 33.4 (7.05)

Table 5 Quality characteristics and collagen content of surimi preparations from broiler and spent hen MDM.

pH value Free water (%) Color: L a b

Collagen (% of total protein)

With connective tissue Broilers

6.4 (0.11) 36.9 (0.30)

54.0(1.31) 8.0 (0.20) 9.3 (0.28)

27.3 (0.50)

Hens

6.5 (0.15) 37.4 (0.21)

56.9 (0.66) 3.8 (0.40) 10.7 (0.05)

30.2 (0.95)

Without connective tissue Broilers

6.45 (0.05) 37.0 (0.30)

39.1 (1.44) 14.1 (3.90) 13.5 (0.70)

0.72 (0.03)

Hens

6.45 (0.09) 37.5 (0.08)

45.8 (0.44) 6.6 (0.59) 13.7(0.19)

0.86 (0.02)

136

hardness IN]

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50

@

6 7 8 9 10 11 12 13 14 15 16 17 protein concentration I%]

hardnesslN]

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100

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Figure 1 Hardness of surimi gels from mechanically deboned spent hen (1) and chicken (2) as a function of protein concentration. Surimi gels without (a) and with (b) connective tissue.

137

138

THE EFFECT IONIC STRENGTH AND PYROPHOSPHATE ON PROTEIN EXTRACTION AND TEXTURE OF SAUSAGES FROM CHICKEN MUSCLES

W. Kopec and T. Smoliriska

Agricultural University of Wroclaw, Department of Food Technology of Animal Origin, Norwida Street 25/27, 50-375 Wroclaw, Poland

Abstract

The effects of a change in the value of ionic strength and partial replacement of NaCl by sodium pyrophosphate in the extraction process on the quantity of monomers and olygomers of myofibrillar proteins isolated from chicken muscle tissue were analyzed. The objectives of the study were rheological properties of the gels produced from chicken muscle tissue. A technological assessment and evaluation of texture of model sausages were conducted. The value of the ionic strength was reduced from m=0.75 to m=0.375. The extraction time ranged from 30 min. to 24 h, 0.5% or 0.25% Na4P207 was added to the meat homogenate thus substituting 50% or 25% NaCl, respectively.lt was found that the change in the ionic strength during the extraction longer than 4 h (2 h high and 2 h low ionic strength) initially increased and then decreased the quantity of extracted proteins, which accounts for the artificial filamentation of myofibrillar proteins. The addition of 0.25 % Na4P207 instead of NaCl improves the rheological properties of gels and extractability of the proteins from breast and leg chicken muscles. Reduced ionic strength during 4 h curing (2 h + 2 h) improves the texture of finely comminuted sausages as compared to the sausages manufactured conventionally.

Introduction

The texture of meat and poultry processed products is affected by muscle proteins, especially myofibrillar undergoing some changes such as swelling, dissolving and gelation during technological processes (Ziegler and Acton, 1984). The quantities of dissolved proteins and components as myofibrils, myofilaments,etc. released from the muscle tissue are a function of the intensity of comminution and the ionic strength affected by the ions of curing salts. (Acton et al., 1983). Myosin dissolves at m =0.3 while actomyosin needs higher ionic strength (m=0.6). Polyphosphates (especially pyrophosphate one of the major components of curing brines apart from NaCl) are important agents improving solubility of actomyosin complex (Knight and Trinick, 1982).Among myofibrillar proteins, myosin

139

and actomyosin in the solutions are able to form artificial filaments or aggregates as the effect of reduced ionic strength (Joseph and Harrington, 1966).In our study this phenomenon was studied to estimate influences on rheological properties of gels of chicken muscle homogenates and subsequent texture of model sausages.

Materials and Methods

The studies were carried out on 196 chicken carcasses. Slaughtering and post-slaughter processing were performed on a commercial slaughter line. The carcasses were frozen-stored at -18 C for 3 weeks. After thawing, the breast and leg muscle were cut off by hand and minced with a grinder. The experiment was divided into 2 parts:

Experiment I: Involved optimization of the extraction time of proteins from chicken muscle homogenates, under changing ionic strength from a high to a low value.The extraction time for the constant ionic strength was: 30 minutes, 4 h and 24 h. For the various ionic strength (m) from high to low value: 2 h (high m)+ 30 min. (low m), 2 h + 2 h , 2 h + 4h , 4 h + 2 h, 24 h + 2h . After the optimal extraction time was found the replacement of 25% and 50% amount of NaCl by sodium pyrophosphate was studied. The extraction was conducted at a constant value of the ionic strength, i. e. m=0.375 which correspond to 2.2% addition of NaCl or 1.1% NaCl +0.5% Na4P207 or 1.65% NaCl + 0.25% Na4P207. The extraction was also carried out at changing ionic strength from m=0.75 to m=0.375. The muscle tissue homogenates were prepared from minced leg and breast muscle chopped with ice (2:1 w/w and NaCl or NaCl + Na4P207 in a laboratory chopper for 10 minutes. The homogenates for extraction at changing ionic strength were made from 75 parts of muscle chopped with lo parts of ice and salt for 3 min. The homogenates were stored refrigerated for 30 min, 2 h or 4 h (high m) after which 25 parts of muscles and 40 parts of ice were added and chopped for 7 min. After chopping the homogenates were stored refrigerated for 30 min, 2 h or 4 h (low m). In the case of prolonged extraction periods salts were added to the ground meat, then stored refrigerated for 24 h and chopped as above.

Experiment II: Finely and coarsely comminuted model sausages at constant m (curing time: 10 minutes - control, 4h, 24h) and changing m (curing time: 30 min + 30 min, 2 h + 2 h and 24 h + 2 h) were produced with 2.2% addition of NaCl or 1.1% NaCl and 0.5% Na4P207 in relation to the weight of meat. Breast and leg muscles mixed together in 1:1 ratio (100 parts), ice (50 parts) and porcine ground fat (25 parts) in the same way as the homogenates. Apart from NaCl or NaCl and Na4P207 also 50 ppm of NaN03 was added during chopping. After chopping the emulsion was stuffed into collagen casings (f 35mm) smoked and scalded. Coarsely comminuted sausages were made from chicken

140

muscle (55%) minced in a grinder (dry salted for 24 h), ground fat (15%) and finely comminuted emulsion (30%).

Analytical methods

- pH was measured using a pH-meter and a combined electrode - The amount of extracted myofibrillar protein monomers and olygomers was determined

in the homogenates diluted with NaCl or NaCl and Na4P207 solutions in 1:1 ratio and next separated into 3 fractions by centrifugation (1750xg) : supernatant, sol fraction and residue. The monomers and olygomers contents were determined in the supernatant and sol after centrifugation at 80000xg according to Wu and Smith (1987). After reducing the ionic strength of the solutions to m=0.04 the amount of sarcoplasmic proteins was determined and substracted from the sum of olygomers and monomers. The quantitative analysis of proteins was done by biuret method (Gornall et al., 1949).

- Protein content in sausages was determined by the Kjeldahl method, water by drying at 105°C, fat content after ether extraction

- Thermal stability of the emulsions was expressed as the weight loss of samples heated to 70°C and centrifuged (15000xg). Free water content in the sausages as the water squeezed from 5g slices by compression (5 N/cm). Colour of the sausages by Minolta camera (L* a* b*).

- Rheological properties of homogenate gels and sausages were determined using an Instron apparatus. Samples were compressed at 2 degree of deformation: 50% and 75%. Maximal force (hardness) needed to destroy a sample, deformation at maximum force and springiness were calculated from force-time curve.

- Sensory analysis of sausages was conducted by a panel of 6 judges who evaluated colour, texture and palatability using a 5-points scale (indicating also optimal intensity of the attribute).

Results

Changes in pH occurred mainly in the homogenates of breast muscles, eg. from 5.81 to 6.07 after 24h extraction with 0.5% Na4P207. The changes observed in the leg muscle homogenates were smaller. Table 1 shows that during prolonged extraction (4 hours or more), the quantity of protein monomers increases at high m and decreases at reduced m. The amount of the extracted protein monomers was similar at constant or changing m and comparable extraction time.

141

The olygomers were affected by the changes in the ionic strength to much a smaller extent than the monomers. The results of our studies proved that optimal time for protein extraction was 4 h and 6 h. These two period of time and 24 hours were taken into account in further studies in which NaCl was partially replaced (25% and 50%) by Na4P207. The 25% replacement resulted in higher amount of the extracted monomers and olygomers than 50% replacement. Similarly as in the case of extraction with NaCl the extraction with Na4P207 resulted in a decreased quantity of monomers after reducing the ionic strength. The amount of olygomers extracted from breast muscles was higher than from leg muscles.The change in ionic strength during extraction above 4 hours increases the hardness of gels (Table 2). The replacement of 1.1% NaCl by 0.5% Na4P207 (50%) results in reduced hardness of gels from leg muscles but does not affect the hardness of gels from breast muscles. The addition of Na^Oy substituting 25% NaCl increases the hardness of both breast and leg muscles gels. The change in the ionic strength during the extraction with Na4P207 increases the hardness of gels by 10% to 50%. Finely comminuted sausages contained 14.9%-16.3% protein, 16.3%-17.6% fat and about 2.25% NaCl, coarsely comminuted sausages contained 18.5% protein, 21.5% fat and 2.3% NaCl. Sausages produced with Na4P207 addition contained about 1.15% NaCl. The change in the value of ionic strength and curing time did not affect the yield of sausages, although prolonged curing time and changing ionic strength decreased thermal drip and free water content (Table 3). The control sausages exhibited lower lightness (L*) than the others. The redness (a*) decreased with prolonged curing for the sausages made with pyrophosphate. Flavour and odour of the control sausages did not differ from the others but their juiciness was less. The sausages cured with NaCl and Na4P207 were not enough salty (optimum = 3.5) and those cured with NaCl were too salty. The addition of Na4P207 substituting 50% NaCl deteriorated the cohesiveness especially at short curing periods. The best cohesiveness was exhibited by the sausage produced at changing ionic strength during 4 hours (2 h + 2 h) curing. This product had also the optimum hardness, elasticity and grayness. The instrumental texture analysis confirmed the sensory evaluation. It was observed among others that the sausages cured at the changing ionic strength were characterized by higher mechanical resistance i.e. the degree of deformation needed to destroy their structure was higher in comparison with other sausages.

Discussion

Our studies proved that partial replacement of NaCl by the addition of 0,25% Na4P207

(25% substitution of NaCl) results in the increased extractability of myofibrillar proteins and improved rheological properties of the gels from breast and leg chicken muscles. 0.25% addition of Na4P207 corresponding to 10 mM allows for the reduction of NaCl from 0.7 M without changing the swelling of myofibrils (Paterson et al., 1988).Pepper and Schmidt (1975) report that phosphates favourably affect the functional properties of leg muscles whereas our studies show that the use of Na4P207 instead of 50% of NaCl has

142

a positive effect only on breast muscles.The change of the ionic strength resulted in a significant increase of the extracted protein monomers at the phase of high m =0.75 which is optimal for the solubility and gelation of myofibrillar proteins (Yasui et al., 1980). The diminishing quantity of monomers was observed after reducing the ionic strength which accounts for polymerization similar to artificial filamentation of myofibrillar proteins during dialysis of their solutions. Such a phenomenon occurs 4 hours after curing, improving the texture of sausages. Not any deterioration in the yield and thermal stability of sausages for 50% replacement of NaCl by Na^Oy was observed. Barbut et al. (1988) found that 40% reduction in NaCl with complementary 0.4% Na4P207 deteriorated thermal stability of frankfurters but 20% reduction did not increase thermal drip. Bearing in mind the fact that 50% reduction in NaCl (replaced by Na4P207) results in 30% reduction in sodium content of the sausages and low fat content ('17%) the model sausages can be considered as lean products according to the classification reported by Leddy and Wise (1988).

References

Acton, J.C., Ziegler, G.R. and Bürge, D.L., 1983. Functionality of muscle constituents in the processing of comminuted meat products. CRC Crit. Rev.Food Sei. Nutr. 18, 99-121.

Barbut, S., Maurer, A.J. and Lindsay, R.C., 1988. Effects of reduced sodjum chloride and added phosphates on physical and sensory properties of turkey frankfurters. J. Food Sei. 53, 62-66.

Gornall, A. C , Bardawill, C.T. and David, M.N., 1949. Determination of serum proteins by means of the biuret reaction. J. Biol. Chem. 117, 751-754.

Joseph, R. and Harrington, W.F., 1966. Studies on the formation and physical chemical properties of synthetic myosin filaments. Biochemistry. 5, 3474-3487.

Knight, J. and Trinick, J.A., 1982. Preparation of myofibrils structural and contractile proteins. In Methods in Enzymology. Ed. by Frederikson D. W., Cunningham L. W. Academic Press, New York. 85.

Leddy, K.F. and Wise J.W., 1988. Labeling policies for meat and poultry products. Proceed. Recip. Meat Conf. AMSA 41, 21-30.

Paterson, B.G., Parrish, F.C. and Stromer, M.M., 1988. Effects of salt and pyrophosphate on the physical and chemical properties of beef muscle. J. Food Sei. 53, 1258-1265.

Pepper, F.H. and Schmidt G.R., 1975. Effect of blending time, salt, phosphate and hot-boned beef on binding strength and cooking yield of beef rolls. J. Food Sei 40, 227-230.

Wu, F.Y. and Smith, S.B., 1987. Ionic strength and myofibrillar proteins solubilization. J. Anim. Sei. 65, 597-608.

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Yasui, T., Ishioroshi, M. and Samejima, K., 1980. Heat-induced gelation of myosin in the presence of actin.J. Food Biochem. 4, 61-78.

Ziegler, G.R. and Acton, J.C., 1984. Heat-induced transitions in the protein-protein interaction bovine natural actomyosin. J. Food Biochem. 8, 25-30.

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OXIDATIVE CHANGES OF MECHANICALLY DEBONED POULTRY MEAT LIPID COMPONENTS DURING STORAGE

K. Mfkovâ, L. Havlfkovâ and R. Benovsky

Poultry Industry, Sladkovského nam. 3, 130 00 Praha 3, Czechoslovakia

Abstract

Mechanically deboned poultry meat (MDPM) is being used in an increasing amount for manufacturing many types of poultry meat products. The extent of lipid oxidative changes is counted among important quality criteria. In this study the effects of refrigerated and frozen storage, thawing and nitrite-salt mixture addition have been observed. Tlie lipid oxidation was expressed as TBA values. There is no simple relation between the total fat amount and TBA value. The extent of lipid oxidation depends on the type of raw materials (fresh or frozen, broilers or turkeys) and on the ratio between skin and meat content. During storage in the refrigerator (+4°C) no significant changes of TBA values have been stated during 48 hrs with raw materials which were fresh or frozen stored for a short time (3 months). The same results have been obtained after 6 months, storage in freezer (-18°C). The fat oxidation rate of frozen MDPM has enhanced significantly during thawing. Tlie nitrite-salt mixture addition to MDPM has had no anti-oxidative effect.

Introduction

Mechanical deboning processes have been used in recent years to enhance the utilization of poultry meat by removing the rests of meat from bones. Chicken necks and backs or frames, turkey frames and spent laying hens which are of low market value can be mechanically deboned and used in emulsified and other processed food products. Mechanically deboned meat (MDM) is characterized by its paste-like consistency and high susceptibility to deteriorative microbial, chemical and biochemical changes which occur during storage. Poultry meat is composed of relatively high levels of unsaturated fatty acids and low levels of natural tocopherols, making it relative unstable to oxidation. It has been reported (Froning, 1970) that heme pigments (biocatalysts for the meat lipid oxidation) and lipid components from bone and skin are incorporated into the resulting meat. Therefore, lipids from these sources may also affect the flavour quality of the meat

149

products and be responsible for stability problems. Factors which affect the rate of off-flavour development include fatty acid composition of lipid, temperature, light, metal catalysts, inhibitory compounds, and availability of oxygen. Lipid content and composition of different poultry tissues vary considerably and influence oxidation potential. Chicken abdominal fat and skin contain several times the total lipid level of thigh and enhance the total lipid content in MDPM. All tissues contain phospholipid material, which oxidized more readily than neutral lipids (Katz et al., 1966). Temperature can affect lipid oxidation in many ways. Refrigerated storage of MDPM delays or slows down the oxidation rate, and frozen storage further inhibits oxidative reactions but does not stop them completely.

Materials and Methods

All samples of MDPM were obtained from a routine production of Prague Poultry processing plant. Mechanically deboned meats were processed through a Beehive deboning machine. List of samples and their fat and water contents are presented in Table 1. During storage, all samples were held in 250 g aluminium foil packets to prevent light and oxygen access. Moisture content was determined by the microwave oven method. Fat analyses were performed by the Soxhlet extraction (Davidek et al., 1977). TBA values were determined by the method described by Tarladgis et al. (1960). Results are expressed as mg malonaldehyde (MA) per 1000 g meat or fat: mg MA/1000 g = K x absorbance at 531 nm

K = 7.8

Results

Refrigerated storage

Czechoslovak quality standard for MDPM prescribes to process MDPM into meat products within 48 hrs after deboning with regard to the microbial risk. The MDPM samples were stored at +4°C in refrigerator and the TBA values were measured up to 72 hrs. In fresh, short time (to 3 months) frozen, stored raw materials, no significant changes of TBA values were found up to 48 hrs' period. After 72 hrs refrigerated storage the TBA values increased, but this enhancement was not very clear. As an example, the lipid oxidative changes in MDM from fresh chicken frames and wings with skin are presented in Table 2. On the contrary, MDM from long time frozen stored raw material was oxidized very rapidly (Table 3).

150

Frozen storage

The utilization of frozen MDPM in poultry meat product processing plants is restricted but not excluded. Therefore, the extent of lipid rancidity was studied during one year frozen storage at -18°C. In frozen conditions the oxidation rate is suppressed, nevertheless the TBA values show changes depending on storage time. The oxidation rate depends on the fat content, the origin of the material, and the treatment of raw material before deboning. In fresh raw materials, the significant increase of TBA values was observed after six months storage (Table 4). The TBA values in MDPM from frozen raw materials were in all cases already higher at the beginning of the storage period than that from fresh raw materials. During frozen storage their enhancement continued (Table 5). This storage experiment clearly demonstrated the highly unstable nature of ground turkey meat with regard to lipid oxidation (Table 6).

Thawing

With frozen storage of MDPM the changes after thawing tightly cohere. Especially in MDPM from frozen raw materials the TBA values enhanced extremely within first minutes after thawing. The time of frozen storage did not influence the extent of the reactions (Tables 7 and 8). The TBA values in thawed MDPM from fresh frozen raw materials were 30 times higher than those in the unfrozen MDPM after 48 hrs storage in refrigerator.

Nitrite-salt mixture addition

Commercial formulations of frankfurters and similar meat products from MDPM contain sodium nitrite, salt and other flavoring components. The nitrite-salt mixture is added to MDPM before further processing to decrease a potential microbial risk and improve colour during refrigerated storage. Of these additives, salt may act as a pro-oxidant while sodium nitrite may act as antioxidant (Froning, 1976; MacDonald et al., 1980; Dawson and Gartner, 1983). In this experiment the addition of nitrite-salt mixture caused the increase of TBA values in all samples immediately after addition. Further changes were not significant (Table 9).

151

Conclusions

Oxidizing lipids cause besides rancid off-flavour, also protein polymerization, insolubilization, polypeptide chain cleavage, amino acid destruction, and the development of additional products with proteins (Funs et al., 1982). Lipid protein interactions alter the functional properties of meat and may cause deleterious changes in final product quality (Sikorski, 1978). From the standpoint of lipid oxidation, the following conclusions and recommendations for MDPM are presented: 1. The content of lipids in MDPM has an wide range (4-26%). The differences in fat

content are due to the variation in raw materials. 2. The actual lipid content in MDPM is not the only factor which determines the level

of oxidative changes during refrigerated or frozen storage. 3. The determining effect on the lipid stability is the lipid composition, the phospholipid

content and the fatty acid profile. 4. The lipid oxidation (expressed as TBA value) is influenced by the presence of

polyunsaturated fatty acids, especially in phospholipids, which are more present in muscles than in skin; therefore the ratio of muscles to skin plays a very important role in MDPM quality.

5. The lipid oxidative changes occur more intensively in turkey MDM with respect to lower levels of natural tocopherols.

6. TBA values in MDPM from fresh raw materials are immediately after deboning even during refrigerated or frozen storage lower than those in MDPM from frozen raw material.

7. Significant changes of TBA values were not observed within 72 hrs at refrigerated storage (+4°C) in MDPM from fresh or short time frozen stored raw materials; MDPM from long time stored frozen raw materials must be processed immediately after deboning.

8. MDPM from fresh raw materials can be frozen stored at -18°C during 6 months without significant quality deterioration.

9. MDPM from frozen raw materials ought not to be allowed to be frozen again. 10. During thawing of frozen MDPM, the TBA values increase rapidly regardless of the

previous frozen storage time; frozen MDPM ought to be processed in frozen state or immediately after thawing.

11. The nitrite-salt mixture addition enhances TBA values in MDPM from fresh as well as frozen raw materials; within 72 hrs no significant antioxidant effect was observed.

152

References

Davidek, J. a kol., 1977. Laboratorni pfiruöka analyzy potravin. SNTL, Praha. Dawson, L.E. and Gartner, R., 1983. Lipid oxidation in mechanically deboned poultry.

FoodTechnol. 37, 112. Froning, G.W., 1970. Poultry meat sources and their emulsifying characteristics as related

to processing variables. Poultry Sei. 49, 1625. Froning, G.W., 1976. Mechanically deboned poultry meat. Food Technol. 30 (9), 50. Funs, J.A., Weiss, V. and Karel, M., 1982. Effect of reaction conditions and reactant

concentrations on polymerization of lysozyme reacted with peroxidizing lipids. J. Agric. Food Chem. 30, 1204.

Katz, M.A., Dugan, L.R. and Dawson, L.E., 1966. Fatty acids in neutral lipids and phospholipids from chicken tissues. J. Food Sei. 31, 717.

MacDonald, B., Gray, J.I. and Gibbins, L.N., 1980. Role of nitrite in cured meat flavor. Antioxidant role of nitrite. J. Food Sei. 45, 893.

Sikorski, Z.E., 1978. Protein changes in muscle foods due to freezing and frozen storage. Int. J. Refrigeration 1, 74.

Tarladgis, B.S., Rearson, A.M. and Dugan, L.R.J., 1960. A distillation method for the quantitative determination of malonaldehyde in rancid foods. J. Am. Oil Chem. Soc. 37, 44.

153

Table 1 Tested raw materials.

65.8 62.9 68.9 78.8 65.6 67.3 69.7 70.7

70.7

64.1

20.7 25.2 11.6 4.5

19.0 18.4 12.9 10.5

10.5

22.8

Sample no. Source of MDPM Water (%) Fat (%)

1 chicken wings and backs with 30% of skin - fresh

2 chicken frames with skin - fresh 3 hens - frozen 4 chicken stomachs - frozen 5 chicken thighs with skin - frozen 6 chicken frames with skin - frozen 7 turkey frames - frozen 8 turkey frames - frozen 9 turkey frames frozen with 20%

of nitrite-salt mixture addition 10 chicken frames and wings with

skin - fresh 11 chicken frames and wings with

skin, fresh, with 2% of nitrite-salt mixture addition 64.4 18.7

Table 2 Lipid oxidative changes in mechanically deboned meat from chicken frames and wings with skin (fresh) during refrigerated storage (+4°C) expressed as TBA values.

Storage time TBA values (hrs) MDM Fat

Ö 0.148 0.663 24 0.156 0.683 48 0.148 0.663 72 0.211 0.936

154

MDM

6 513 7 995 9 165

10 335 11 973

TBA values Fat

56 160 68 796 78 936 88 959

103 272

Table 3 Lipid oxidative changes in mechanically deboned meat from hens (frozen) during refrigerated storage (+4°C) expressed as TBA values.

Storage time (hrs)

Ö 20 28 42 66

Table 4 Lipid oxidative changes in mechanically deboned meat from chicken frames with skin (fresh) during frozen storage (-18°C) expressed as TBA values.

Storage time (days)

I 33 64 101 192 216 296 366

MDM

0.117 0.164 0.171 0.195 0.351 0.858 1.404 1.630

TBA values Fat

0.551 0.890 0.929 1.033 1.950 4.680 7.683 8.889

155

Table 5 Lipid oxidative changes in mechanically deboned meat from chicken stomachs (frozen) during frozen storage (-18°C) expressed as TBA values.

Storage time (days) MDM

0.234 0.312 0.295 0.312 0.351 0.663 0.810

TBA values Fat

5.187 6.942 6.556 6.942 7.800

14.742 17.667

1 33 59 100 194 303 365

Table 6 Lipid oxidative changes in mechanically deboned meat from turkey frames (frozen) during frozen storage (-18°C) expressed as TBA values.

Storage time (days) MDM

6.201 12.987 14.508 15.600 16.419 17.082 18.252

TBA values Fat

48.087 100.659 112.476 120.978 124.558 132.405 141.492

0 41 65 121 199 260 367

156

MDM

6.201 7.644 8.346 9.438

10.216

TBA values Fat

53.586 65.910 71.955 81.354 83.023

Table 7 Lipid oxidative changes in mechanically deboned meat from hens (frozen) after 30 days frozen storage (-18°C).

Storage time (minutes)

(f 40 80 180 220

* measured after sample thawing (thawing took 2 hrs at room temperature).

Table 8 Lipid oxidative changes in thawed mechanically deboned meat from hens (frozen) after 60 days frozen storage (-18°C).

Storage time TBA values (minutes) MDM Fat

(T 6.396 55.107 40 7.293 62.049 80 8.303 71.877

* measured after sample thawing.

157

Table 9 Lipid oxidative changes in mechanically deboned meat from chicken frames and wings with skin (fresh) during refrigerated storage (+4°C) expressed as TBA values.

Storage time (hrs)

0 24 48 72

MDM

0.148 0.156 0.148 0.211

TBA values Fat

0.663 0.683 0.663 0.936

MDMN0-+»

2

0.407 0.452 0.398 0.468

FatNO-+> 2

2.251 2.418 2.145 2.496

+) with 2 % of nitrite-salt mixture.

158

THE EVALUATION OF LIGHT HEN AND BROILER MEAT FOR PRODUCTION OF HIGHLY COMMINUTED SAUSAGES

T. Skrabka-Blotnicka

Academy of Economics, 53-345 Wroclaw, Komandorska 118/120, Poland

Abstract

No significant differences have been found between meat yield from broilers and light hen carcasses, and their basic chemical composition. Stable emulsions were obtained for hen meat when the Water/Protein ratio (W/P) <5.10, and for broiler meat when W/P <5.8. The maximum value of the Fat/Protein ratio (F/P) at which stable systems for both meats have been obtained was 1.29. The optimum chopping time was 3-5 min. shorter in case of broilers, and the viscosity of broiler meat emulsions had lower values than hen emulsions. The rheological and organoleptic properties of highly comminuted broiler sausages were favourable, but hen sausages were regarded as hard and dry.

Introduction

Broiler meat has high water and fat holding capacities (Kijowski and Niewiarowicz, 1978a,b), (Skrabka-Blotnicka, 1986). It is used for production of highly comminuted sausages. Broiler meat is eagerly bought unprocessed because of its culinary and taste values. Light hen meat, however, which can be treated as a by-product of egg producing farms, is little juicy and hard, thus customers are not keen on buying it. The meat should be either treated with conditions improving its culinary values or processed into an acceptable product. Attempts to use hen meat (40-60% of raw material) for production of coarse and highly comminuted sausages with addition of beef and/or mutton and fat were acceptable only in case of highly comminuted sausages (Zakrzewski and Mroczek, 1982). Questions arise whether it is possible to produce highly comminuted sausages using only hen meat and what is the usefulness of the meat for producing highly comminuted sausages in comparison to broiler meat. Highly comminuted sausages made from broiler meat and poultry fat with comparable W/P and F/P of the meat emulsion, were characterized by a lower yield and by organoleptic evaluation they were softer than with pork back fat (Baker et al., 1969). For this reason in preparing model emulsions and sausages hen fat was used as raw material.

The work objective was to evaluate suitability of broiler and light hen meat for production of highly comminuted sausages.

159

Materials and Methods

The following materials were used in the experiments: 1) broiler and light hen's carcasses (1.2 kg) from industrially slaughtered birds chilled and stored for 24h at 4°C, 2) hen fat. The yields of breast (BM) and thigh muscles with skin (TM) were determined by cutting and weighing respective muscles from 4 portions of bird carcasses. Nine variants of model tests for each kind of poultry meat - BM and TM mixed in ratio of 1 to 1.1 - were made with the different water and fat additions evaluated in % of meat weight (20, 25, 30%). The organization of experiments, the curing mixture composition, the way of preparing of model meat emulsions and sausages, determination of: protein (P), fat (F), water (W) contents, rheological properties of model sausages, meat emulsion viscosity (?;) and organoleptic evaluation of sausages were the same as described by Skrabka-Blotnicka (1989). The emulsion stability of meat homogenate (ES) and the emulsion stability of meat emulsion (ESM) were determined as described by Townsend et al. (1968). The yield of sausages (Y) was calculated in this way:

Y = m/mb x 100%

where: m - and mb - weight of sausages after and before heating respectively.

Results and Discussion

The results of breast muscles yield and thigh with skin muscles yield are presented in Table 1. There are no significant differences between yield of respective muscles of hens and broiler. It should be noted, however, that musculature of hens in each particular series was more differentiated than broiler.

Characteristic of Raw Material

Characteristic of raw material was carried out by determination of water, protein and fat contents, and stability of meat homogenate emulsion. Because the ES is a very good indicator of water and fat holding capacities of highly comminuted meat - water - fat systems (Lesiow and Skrabka-Blotnicka, 1988), (Skrabka-Blotnicka, 1986). On the basis of determinations of water (W), protein (P) and fat (F) ratios W/P and F/P of meat emulsion were calculated. The values of these determinations are given in Table 2. W, F and P contents in hen and broiler meat do not differ significantly and agree with the results given by Trojan and Kijowski (1975). Broiler meat had a higher water holding capacity than hen meat and a lower fat holding capacity.

160

Determination of Boundary Values W/P and F/P of Meat Emulsions

In a complicated colloidal system such as a meat emulsion, W, F and P contents play big roles. Honikel (1982) says that minimum water and fat losses appear in strictly determined ratios of meat, W and F. In earlier research Skrabka-Blotnicka (1989) found out that there are boundary values of W and F contents in meat emulsion represented by ratios W/P and F/P, and when they are exceeded meat emulsions become unstable, jelly and/or fat releases while heating. Boundary values, of W/P and F/P ratios have been determined on the basis of organoleptic evaluation of sausages. Broiler meat emulsions were stable at higher values W/P=5.8 than hen meat emulsions 5.10. This result was expected because broiler meat has been characterized by higher water holding capacity than hen meat. The boundary value F/P at which one can obtain stable emulsions was 1.29 for both kinds of meats tested.

Determination of Optimum Chopping Time

The optimum chopping time is according to Gorbatov (1981) a time at which Theological properties of chopped emulsions become extreme. Brown and Toledo (1979) however, define the optimum chopping time as a time after which chopped meat emulsions are characterized by the least thermic release, hence they have the highest stability (ESM). That is why both mentioned factors have been determined. The final chopping temperature has an essential influence on emulsion stability, (Skrabka-Blotnicka, 1990), so all tests have been executed at 12±0.5°C. Out of tested properties only meat emulsion stability expressed as the water release volume (ESMW) changed within the prolongation of chopping time. The optimum chopping time has been determined on the basis of the ESMW value - the lowest value. Townsend et al. (1971) stated that viscosity of meat emulsions can not be the factor of control nor determining optimum chopping properties, such as time and temperature. This is due to the fact that while chopping water - meat - fat systems, stability changes are not reflected by changes in viscosity of the systems. Tested meat emulsions display similar characteristics. Measurements of mentioned factors were taken at the moment of getting homogeneous macroscopic emulsions and emulsions chopped time 2.4 and 6 min longer. This is why in Table 3 chopping times for both kinds of meat are different. The optimum chopping time of broiler meat emulsion(W/P=5.21; F/P = 1.29) was 15 min and in case of hen meat (W/P=5.10; F/P=1.29) 18 min. The optimum chopping time for broilers at similar conditions was 3-5 minutes shorter (in case of broilers) than for hens.

161

Yield and Rheological Properties of Sausages

Values of rheological properties and yield of sausages after heating made from meat emulsions at optimum chopping time are shown in Table 4. Sausages made from hen meat emulsions with comparable values W/P and F/P have been characterized by two fold higher values 5K and 5um than those made from broilers and several times higher Dum

values. The obtained rheological results supported the results of an organoleptic evaluation. The broiler sausages were favourable (4 points at 5 point scale) where hen sausages were regarded as hard and dry. The sausages' yield after heating was 14% higher in case of broiler meat than hen meat. Higher values of rheological properties of hen meat sausages are due to a greater water release during heating (lower yield). As a result sausages with lower water content (57.7 to 58.9) than in case of broiler meat (63.5 to 64.8) are obtained.

Conclusion

Broiler meat is more suitable for production of highly comminuted sausages. Together with hen fat it may be used for production of sausages with great yield, good organoleptic, dietetic and rheological values. Hen meat, however, can be used as one of the components of protein materials, to increase its water holding capacity during heating.

References

Baker, R. C , Darfler, J., Vadera, D. V, 1969. Type and level of fat and amount of protein and their effect on the quality of chicken frankfurters. Food Technol. 23, 808.

Brown, D. D, Toledo, R. T., 1975. Relationship between chopping temperatures and fat and water binding in comminuted meat batters. J. Food Sei. 40, 1061.

Garbatov, A. V., 1981. Isledovanija v oblasti inzyniernoj miechaniki miasnych produktov. Mjasnaja Ind. SSSR. (3),26.

Honikel, K. O., 1982. Wasserbindung und "Fettemulgierung" bei der Verarbeitung zu Brathwurstbraten. Fleischwirt. 62, (6), 16 and 19 - 22.

Kijowski, J, Niewiarowicz, A, 1978a. Emulsifying properties of proteins and meat from broiler breast muscles as affected by their initial pH values. J. Food Technol. 13, 451.

Kijowski, J, Niewiarowicz, A., 1978. Effect of initial pH in broiler breast muscles on gel forming capacity of meat proteins and rheological characteristics of frankfurter -type sausages. J. Food Technol. 13, 461.

162

Lesiow, T., Skrabka-Blotnicka, T., 1988. Zaleznosc miedzy wlasciwosciami technologocznymi miesni piersiowych kaczek przechowywanych zamrazalniczo, a stabilnoscia i wlasciwosciami reologicznymi farszu przed i po ogrzaniu. Chlodnictwo 23, 14.

Skrabka-Blotnicka, T. 1986. Wlasciwosci emulgujace i zelujace bialek drobiowych ze szczegolnym uwzglednieniem drobiu wodnego. Prace Naukowe AE Wroclaw nr 358 seria Monografie i opracowania nr. 38.

Skrabka-Blotnicka, T., 1989. The effect of water, fat, and protein levels of the chicken batters stability and Theological properties of chicken batters and sausages. Proceedings Hohenheimer Geflügelsymposium, Stuttgart. 183.

Skrabka-Blotnicka, T., 1990. Wlasciwosci reologiczne drobnorozdrobnionego farszu przed i po ogrzaniu. Cz II Wplyw skladu chemicznego i parametrOw procesu kutrowania. Gospodarka Miesna (10), 14.

Townsed, W. E., Witnauer, L. P., Riloff, J. A., Swift, C. E., 1968. Comminuted meat emulsions. Differential thermal analysis of fat transitions. Food Technol. 22, 319.

Townsed, W. E., Ackerman, S. A., Witnauer, L. P., Palm, W. E., Swift, C. E., 1971. Effects of type and levels of fat and rates and temperatures of comminution on the processing and characteristics of frankfurters. J. Food^Sci. 36, 261.

Trojan, M., Kijowski, J., 1975 Wartosc odzywcza miesa drobiowego Drobiarstwo (3), 6. Zakrzewski, E., Mroczek,J., 1982. Przydatnosc miesa kur do wyrobu kielbas.

Gospodarka Miesna (9), 21.

163

Table 1 The yield of chicken and hen muscles in % of carcass weight.

Poultry kind

Chicken Hen

BM

X

13.7 14.5

s

0.23 1.23

TM

X

15.1 15.8

s

0.49 1.10

TM/BM

1.10 1.12

x-average value of 4 portions -hen 10, -chicken 15 carcasses in one portion: 5 standard deviation.

Table 2 Characteristic of broiler and hen meat and hen fat.

MeatT/M =1 . 1 Fat Chicken Hen

Determination

Water % Fat % Protein % ES cm3

water release oil release

X

74.41 6.8

18.5

11.8 13.9

s

0.97 0.34 1.20

1.44 1.16

X

73.7 7.2

19.0

13.1 10.2

s

0.42 0.57 0.39

1.07 2.03

X

20.8 72.0

1.9

s

1.46 1.05 0.24

x-average value of 18 determination. S = standard deviation.

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Table 3 The influence of chopping time on the viscosity (i?) and emulsion stability of meat emulsion.

w p

5.48

5.48

5.21 5.10*

5.21 5.10*

E P

1.29

1.11

1.29

1.11

Para­meter Time min

ToC

V

ESMW

ESMf

ToC

V ESMW

ESinf T°C

V ESMW

ESMf T°C

V ESMW

ESMf

Broiler meat emulsion

13

12.0 325 5.80 3.00 11.5 345 4.30 2.20

15

12.0 180 5.03 3.50 12.0 185 3.90 2.50

12.5 250 4.10 2.20 12.0 270 4.90 2.50

17

12.0 195 6.80 3.80 12.0 220 4.80 2.70 12.0 265 4.50 2.20 12.0 325 5.50 2.30

19

11.5 200 7.40 2.90 11.5 210 5.70 2.60

12.0 325 5.00 2.80 12.0 360 5.80 2.50

Hen meat emulsion

16

11.5 585 3.00 3.00 11.5 600 3.60 1.35

18

11.5 604 2.10 2.95 12.0 585 3.00 1.95

20

11.5 620 3.20 3.25 12.0 600 4.20 2.00

22

12.0 604 3.50 3.20 12.0 620 4.50 2.00

The viscosity (r;) [Pas] - was determined at shear rate D = 1.5[s"1]: ESMW - volume of water release cm3/25 g meat emulsion; ESMf - value of fat release cm3/25 g meat emulsion; * - data for hen meat emulsion. The data are average values of 2 tests.

165

Table 4 The influence of W and E in meat emulsion on the yield and the rheological properties of sausages.

w p

5.48* 5.48* 5.22* 5.22* 5.10+

5.10+

E P

1.29 1.11 1.29 1.11 1.29 1.11

6k[kPa]

55.72 64.67 67.00 72.00 127.4 143.3

pumio-

7.18 4.39 3.69 3.29 4.54 3.07

"[Pa1] Dum10-

1.41 0.98 1.82 1.57 7.94 9.79

'[Pa"1] Sum[kPa]

-3.92 4.68 3.39 7.00 9.0

U(%)

94.7 95.7 93.9 93.8 80.2 80.0

The data are averages values of 2 tests. 5 - yield point, Pum, Dum, 5um, - apparent fluidity, elasticity, plasticity respectively. * - data for broiler meat. + - data for hen meat.

166

WASHING PROCEDURE TO REMOVE FAT AND COLOUR COMPONENTS FROM MECHANICALLY DEBONED TURKEY MEAT

T. Trziszka, A.K. Popiel and B. Kulpa

Agricultural University of Wroclaw, Department of Food Technology of Animal Origin, ul.C.K. Norwida 25/27, 50-375 Wroclaw, Poland

Abstract

Two methods of 4-stage extraction were used for mechanically deboned turkey meat (MDTM): complete water extraction and carbonate buffer for the second stage of extraction. The purpose of the experiment was to obtain an isolate of myofibrillar protein (IMP) of surimi type and to determine some technological properties of the product. The study included the determination of extraction yield, colour of the initial material and IMP, dry matter and protein contents. IMP supplemented with 1.5% NaCl was heated at 75''C for 30 minutes. The gel samples were tempered and stored at 6°Cfor 12 h. Weight losses and free water content of the gel were determined, hardness of the gel was measured by penetrometric method and sensory analyses were conducted. The studies prove that the yield of IMP is higher with carbonate buffer (62.4%) in comparison with water extraction (52.9%). Dry matter and protein contents were lower in IMP after carbonate buffer extraction in comparison with those noted for water extraction, i.e. 9.8 and 8.9%, respectively 11.8 and 9.6. The lightness (L*) significantly increased but the redness (a*) was significantly reduced by comparing the initial material. The lowest weight losses due to heat treatment were observed in the isolates obtained by water extraction. Hardness and elasticity of the gels were the best in the isolates after water extraction. It was found that 20% - 50% of IMP can substitute meat for hamburger production without deteriorating the sensory attributes of the finished product.

Introduction

Increasing interest in mechanically deboned poultry meat (MDPM) recognized as a source of highly functional protein isolates requires continuous search for new extraction methods of myofibrillar proteins based on surimi technology. However, surimi technology commonly used in fish industry, cannot be directly transferred to poultry processing. The

167

main obstacles which interfere with its acceptance for poultry meat are as follows: comminution (Acton, 1972), high contents of heme compounds, the presence of dispersed fat and connective tissue. So far, many attempts have been made to remove the heme compounds from MDPM by various washing methods. Warris (1979) extracted the heme compounds using a phosphate buffer and found this process to be most effective at pH above 6.8. Dawson et al. (1988) used 0.5% sodium bicarbonate, 0.1% acetate buffer and tap water in order to remove the heme pigments and fat from MDPM. Most effective proved to be sodium bicarbonate. The purpose of our studies was to determine some technological properties and nutritive value of myofibrillar protein isolates obtained by the method of aqueous extraction and extraction in carbonate buffer.

Material and Methods

The material selected for the study included mechanically deboned turkey meat (MDTM), from turkey frames. Deboning was conducted at 4°C using a Stork Protecon deboner. Immediately after deboning, MDTM was packaged in polyethylene bags (2 kg in each bag), frozen and stored at -18°C. Prior to extraction MDTM was thawed at 2°C for 24 h. The extraction was performed using tap water and carbonate buffer.

Rinsing with water

200 g MDTM batches were thoroughly mixed with 100 g of water and centrifuged in a K 70 D centrifuge at 1750xg, 5°C for 10 min. The layer of fat and supernatant were discarded. The procedure was repeated twice, with water added in the ratio 2:1 (w/w). The slurry was passed through a 1 mm mesh screen, diluted with water (ratio 2:1 w/w) and adjusted with 0.1 N HCl to pH 6.0. If necessary, the suspension was centrifuged at 1750xg for 15 minutes.

Rinsing with carbonate buffer, pH 9.2

This operation was nearly similar to the rinsing with water but at the second stage, 0.1 M bicarbonate buffer (pH 9.2) was employed (temp.4°C, w/w ratio 2:1).

The initial material and the myofibrillar protein isolates were subjected to the following analyses:

168

Chemical determinations

Dry matter content was determined by drying method at 105°C. Protein content was determined by the Kjeldahl method (conversion coefficient 6.25).

Colour measurements

L*, a*, b* values were determined using a reflectance colorimeter Minolta CR 200 b.

Gel production and characteristics

Twenty g of the isolate supplemented with 1.5% of NaCl were heated at 75°C for 30 minutes, cooled with tap water and stored in a refrigerator at 6°C until the next day.

Weight losses of gels

The weight losses of gels were calculated from the difference in weight before heat treatment (20.00 g) and the weight of gels after heat treatment and separation of the unbound water.

Free water content of gels

Free water content of gels was determined using a punch test (Whatman's 1 blotting paper). 5.2 g gel samples were subjected to the compression of 10 N/cm for 10 minutes. Free water content was calculated from the difference in gel weight before and after compression.

Penetrometric measurements of gels

The measurements were carried out using a LPU 3 penetrometer (USSR) with a flat-walled plunger (5 mm in diameter). The hardness of gels (A) is expressed as % of plunger penetration (Synowiecki, Sikorski, 1983).

169

h rh0

A = , where H;-h„ Al " o

H - height of gel sample, h0 - height of unloaded plunger after 30 s penetration, hi - height of loaded plunger after 30 s penetration.

Folding test

3 mm gel slices (15 mm in diameter) were folded twice. Cracking of the samples was evaluated using a 5-point scale after Nippon Suisan Kaisha, Ltd.(Lee, 1980).

Hardness

Hardness of gels was evaluated sensorially by a panel of 4 judges using a 10-point scale after Nippon Suisan Kaisha, Ltd.(Lee, 1980).

Production of hamburgers and sensory evaluation

Hamburgers were made from IMP (after carbonate buffer extraction) and minced chicken leg and breast muscles (mixed in w/w ratio 1:1) in 4 variants. Variant 1-100% chicken mince, Variant 2 - 8 0 % chicken mince + 20 % IMP, Variant 3 - 50% chicken mince + 50 % IMP, Variant 4 - 2 0 % chicken mince + 80 % IMP. Chicken leg and breast muscles were chopped in a mincer (3 mm mesh). Each variant was supplemented with 5% potato starch and 0,3% sodium pyrophosphate. Hundred g hamburgers were hand-shaped and fried in oil at 175°C for 6 minutes. The sensory evaluation took place the same day. It was conducted by a panel of 8 judges who evaluated elasticity and hardness (1- slightly elastic and hard, 3- optimum, 5- too elastic and hard), flavor, overall acceptability and juiciness (1- least desirable, 5- most desirable).

170

Statistical analysis

The data obtained in the study were analyzed statistically using one-way analysis of variance (LSD, a=0.05), Statgraphics ver. 2.1.

Results and Discussion

The major factors determining methods of rinsing are: the yield of IMP (% in relation to MDTM) and its technological value. Better yield (Table 1) was noted for the extraction with carbonate buffer (62.4%) than tap water (52.9%). The yield of the finished product is related with the quality and chemical composition of the initial material as well as extraction method, which was confirmed by other authors (Kijowski, 1989; Ball and Montejano, 1984). Extraction of MDTM changed its chemical composition and colour significantly. Rinsing with water and carbonate buffer reduced dry matter and protein contents significantly (a=0.05). Similar results were reported by Dawson et al. (1988). The extraction increased the lightness (L*) but reduced the redness (a*) of IMP in comparison with MDTM. Neither of the methods affected the lightness of the colour which was likely due to a relatively light colour of the initial material. Similar results were obtained by Warris (1979) and Hernandez et al. (1986) who reported that heme pigments were not washed out effectively. Also Dawson et al. (1988) found that 0.5% bicarbonate solution was more effective in reducing the heme pigments in mechanically deboned poultry meat. Table 2 shows gel characteristics after heat treatment at 75 °C for 30 minutes. The gels produced from IMP after rinsing with carbonate buffer exhibited significantly increased lightness of the colour and in comparison with IMP rinsed with water. Similar data were reported by Hernandez et al. (1988). The gelatinized IMP washed with carbonate buffer exhibited higher weight losses due to heat treatment in comparison with the IMP washed with tap water, although the free water content determined for the two isolates was almost the same. The differences in the weight losses due to heat treatment can be attributed to reduced dry matter and protein contents of the IMP obtained by carbonate buffer isolation. The penetrometric and folding tests as well as the test on hardness indicate that the parameters noted for IMP washed with tap water are slightly better than those for carbonate buffer. This is probably due to higher dry matter and protein contents of the aqueous isolates. The sensory evaluation of the hamburgers made from chicken mince supplemented with IMP isolated with carbonate buffer is shown in Table 3.

171

In general, the sensory attributes show that 50% addition of IMP obtained from MDTM rinsed with carbonate buffer does not reduce the acceptability. It improves the texture of the hamburgers produced. It seems that further improvements in the methods for MDTM extraction, especially increasing yield and protein content of the IMP can improve the technological characteristics of the finished product.

References

Acton, J.C., 1972. The effect of meat particle size on extractable protein, cooking loss and biding strength in chicken loaves. J. Food Sei. 43, (1), 240-243.

Ball Jr., and Montejano, J.G. 1984. Composition of washed broiler thigh meat. Poultry Sei. 63, (Suppl. 1), 60.

Dawson, P.L., Sheldon B.W., Ball Jr., H.R. 1988. Extraction of lipid and pigment components from mechanically deboned chicken meat. J. Food Sei. 53, (6), 1615-1617.

Hernandez, A., Baker, R.C., Hotchkiss, J.H., .1986. Extraction of pigments from mechanically deboned turkey meat. J. Food Sei. 51, (4), 865-872.

Kijowski, J. 1989. Attemps at obtaining the wet concentrate of myofibrils from chicken breast and mechanically deboned poultry and its functional properties. Acta Alimentaria Polonica. 34, (4), 317-326.

Lee, CM. , 1984. Surimi process technology. Food Technol. 38, (11), 69-80. Synowiecki, J., Sikorski, Z.E., 1983. Proba okreslenia przyczyn nieporzadanych zmian

mroxonego miesa dorsza. Przemysl Spoxywczy 37, (3), 127-129. Warns, P.D., 1979. The extraction of heme pigment from fresh meat. J. Food Technol.

14, 75.

172

MDTM

FAT, WASTE *-

CONNECTIVE

TISSUE

« 1. WATER 0 . 5 : 1

2 . EFFLUENCE 2 : 1

- WATER

- CARBONATE BUFFER PH~9 .2

3 - WATER 2 : 1

STIRRING <—

I CENTRIFUGATION

I PASSING THROUGH + WATER 2 : 1 THE SCREEN

ADJUSTMENT PH - 6.0 + 0.1 M HCL

WASTE *- CENTRIFUGATION

IMP

Scheine 1 Flowchart for washing procedure of MDTM.

173

Table 1 Characteristics of MDTM and IMP after water and carbonate buffer extraction.

Dry Protein Yield1 Colour matter content (%) L* a* b* (%) (%)

Unwashed MDTM - 58/7 2L8 ïsl 33^2 15^9

Rinsing with water 52.9 62.2a 14.2" 11.1" 11.8a 9.6a

Rinsing with carbonate buffer 62.4 62.4" 9.1 8.9b 9.8b 8.9a

'IMP yield in relation to MDTM (initial material). The same letter in a column means that the difference is not significant (o=0.05).

Table 2 Characteristics of gels from IMP after heat treatment at 75°C for 30 minutes.

Weight Free Folding Hard-Extraction Colour losses water A test ness method L* a* b* (%) (%) (%) (1-5) (1-10)

Water 67.4a 4.8a 14.8a 25.9a 19.8a 9.1a 2.8a 3.8a

Carbonate buffer 69.8b 4.0b 14.7a 35.4b 19.7a 15.8b 2.7a 3.0b

The same letter in a column means that the difference is not significant (a=0.05).

174

Table 3 Organoleptic assessment of hamburgers with different addition of IMP (n=8).

Variant 1

Variant 2

Variant 3

Variant 4

Elasticity1

4.5

3.6

3.3

2.9

Firmness1

4.7

3.6

3.1

2.8

Flavour2

3.7

3.3

3.1

2.8

Accep­tability2

2.9

2.9

2.8

2.6

Juiciness2

3.1

3.1

3.0

3.1

'Optimum - 3, 2optimum - 5

175

USE OF Na2C03/NaHC03 BUFFER FOR THE EXTRACTION OF MYOFIBRILLAR PROTEINS FROM MDPM AND THE INFLUENCE OF FREEZING ON THE FUNCTIONAL PROPERTIES OF THE ISOLATES

T. Trziszka1, T.G. Uijttenboogaart and F.J.G. Schreurs

Spelderholt Centre for Poultry Research and Information Services, Agricultural Research Service (DLO), 7361 DA Beekbergen, The Netherlands 1 Agricultural University Wroclaw, Department of Food Technology, Wroclaw, Pl-50-375, Poland

Abstract

Mechanically deboned meat from spent layer necks was extracted in 4 steps with Na2C03/NaHC03 buffer, pH 9.2. During the 3rd extraction the pH was decreased to 5.5 or 6.0. From the produced isolates a control sample and samples mixed with 2 types of cryoprotectants were frozen and stored at -21 °C during 30 days. The functional properties of the unfrozen as well as the frozen products were determined. Extraction yields at pH 5.5 and 6.0 were 36.5 and 45% (wet base) or 30.5 and 24.5% (dry base) respectively. The extracts produced at pH 6 showed better emulsifying and water binding properties, lower weight losses during heating and better texture properties. Use of cryoprotectants had a positive effect on gel texture.

Introduction

Recent developments in the poultry industry, e.g. the increasing consumption of further processed poultry products in the western countries, introduce special problems in valorization of the stripped carcasses. These carcasses still contain about 30% muscle tissue as well as skin, connective tissue and bone. Nowadays, the stripped carcasses are used for the production of Mechanically Deboned Poultry Meat (MDPM). Up to 2 0 - 25% MDPM is used in different types of products, e.g. frankfurters, sausages, etc (Baker and Kline, 1984). Higher percentages can cause problems related to oxidation of fat.

177

In recent years, especially in the US research is conducted to find other ways to increase the value of MDPM (Dawson et al., 1989, Hernandez et al., 1986, Kijowski, 1989). One option is the extraction of myofibrillar proteins, based upon the old Japanese way of extraction of myofibrillar proteins from fish: the production of "surimi" (Lee, 1984, Lee, 1986, Lanier, 1986, Mackie, 1982, Scott et al., 1988, Wray, 1987). The technology of surimi production has been modified and improved. Especially the use of cryoprotectants like sorbitol and saccharose increased the possibilities to maintain the good functional properties of myofibrillar protein isolates during a longer period if stored at temperatures below 0°C.

The use of the surimi technology however cannot be used integrally for the extraction of myofibrillar proteins from MDPM for following reasons: 1. Raw material Surimi is produced from deboned fish meat, which is a low fat, low connective tissue and colorless product. MDPM contains more fat (10-30%), has a high connective tissue content and contains myoglobin that is responsible for the red color of chicken meat. The myofibrillar fraction of MDPM is smaller than of fish meat. 2. Extraction procedure For the production of surimi water or a salt solution is used. Because of the presence of fat, coloring agents and connective tissue other methods need to be used to produce myofibrillar extracts from MDPM. 3. Environmental problems During the extraction of myofibrillar proteins from MDPM a residue is obtained containing fat, connective tissue, coloring agents, salts and components required to carry out the extraction. An important factor minimizing the amount of water is the number of extraction stages and volumes of the extraction solutions used. 4. Marketing of the extracted products It is important to develop cheap and simple methods to extract high quality myofibrillar protein isolates from low value MDPM.

In this study MDPM from spent layer necks are extracted with a Na2C03/NaHC03 buffer (pH 9.2). The obtained Myofibrillar Protein Isolate (MPI) was frozen after addition of cryoprotectants. Yield and functional properties of the MPI are estimated.

Materials and Methods

MDPM was produced from spent layer necks with a Protecon deboner. The extraction was executed with water and Na2C03/NaHC03 buffer according to diagram 1. During the third extraction step the pH was adjusted to 2 different pH levels (5.5 and 6) by 1 N HCl.

178

The produced MPI was partly used frozen with and without cryoprotectants (4% sorbitol/4% saccharose or 0.5% monosodium glutamate/0.3% tetrasodium pyrophosphate) and partly unfrozen as shown in diagram 2. The frozen MPI was stored frozen at - 21 °C for 30 days.

During the extraction process the yield was estimated using the formula:

wet weight of the MPI obtained * ioo%

wet weight of MDPM used

The following methods have been used to estimate the composition and quality characteristics of the MPI samples: 1. Dry solids according to ISO 1442 2. Reflection color values L* and a* with the Minolta Chromameter. 3. Emulsifying capacity as described by Mast et al. (1982). 4. Waterbinding capacity as described by Young et al. (1987). 5. Gel forming properties and gel texture.

Before heating 140 g of MPI was mixed with 3.5 g (2.5%) NaCl and 0.42 g (0.3%) sodium pyrophosphate in a Hobart N-50 mixer during 10 minutes, speed setting 1. Exactly 20 g of the obtained paste was put in a plastic tube (4>2l mm, height 72 mm) and heated during 30 minutes at 72°C. After heating the tube was chilled in tap water and stored overnight in a refrigerated room at 4°C. The obtained gels were weighed to estimate heating losses and used for the following texture measurements. Cylinders with a length of 25 mm and ^ 21 mm were used to estimate: a. the shear force (N) with a Warner Bratzler shearing device at a cross head speed of 200 mm/min. b. the maximal force, deformation and elasticity during a pressing procedure as described by Lyon et al. (1980).

6. Differential Scanning Calorimetry (DSC) analysis was carried out with a Dupont DSC system at the NIZO (Netherlands Institute for Dairy Research) laboratory in Ede, The Netherlands.

Results and Discussion

The results of the study are given in Tables 1 to 6. Table 1 shows the characteristics of the used raw material. As can be expected from MDPM produced from spent hen necks the color is rather dark (L*=51.0) and red (a* = 19.4).

179

Table 2 gives the results of the wet weight based pH depending (5.5 or 6.0) yields of the extraction procedure. At pH 6 a higher percentage of MPI was obtained than at pH 5.5 (45 and 36.5% respectively). Dawson et al. (1989) reported much lower results (13.5%) during the extraction using sodium hydrogen carbonate. Compared with his result, the obtained yield is promising. Extraction at different pH-values did not effect connective tissue, fat and oil fractions. There was a significant difference in the soluble fraction (waste). At pH 6 the percentage was almost 8% lower. However, this is to be expected at a higher MPI yield. In Table 3 the results of the analysis of the MPI and some functional properties are given. MPI showed a higher dry solids content than that of the original MDPM. These results do not agree with those reported by McCurdy et al., 1986 and Ozimek et al., 1986 who found lower dry solids content of MPI. Taking into account the dry solids content at pH 5.5 and pH 6.0 MPI (respectively 30.5 and 24.6%) and the yields (respectively 36.5 and 45.0) of both extraction methods lead to the same myofibrillar protein yield. The color values L* and a* differed significantly. The pH 5.5 extract was lighter and less red. The pH 6.0 extract showed better emulsifying and waterbinding capacity. McCready and Cunningham (1971) showed that emulsifying capacity is very depending on the pH. Optimum pH is about 7. This is in good agreement with the results found in this study. Table 4 shows the results of the cooking losses of the unfrozen and frozen MPI extracts, the latter with and without cryoprotectants. Generally the pH 6 extracts show lower cooking losses and there is also an effect of the cryoprotectants. Frozen MPI with cryoprotectants shows the same cooking losses as the unfrozen product. Textural properties from the MPI gels are given in Table 5. Gels prepared from frozen MPI extracted at pH 5.5 have not been estimated. Comparison of the maximum force data during pressing and the shear force of the gels prepared from the pH 5.5 and 6 respectively showed a firmer gel from the latter. For these data the effect of cryoprotectants is also very clear. Almost the same values were found for the gels with the cryoprotectants as for the gel from unfrozen MPI. The values for the maximum force during pressing of more than 40 N are of the same order as the data found by Lanier (1984) for surimi isolates from red hake and silver hake. The results of the DSC analysis are given in Table 6. Freezing with cryoprotectants affected the temperatures of MPI phase transition, i.e. Tmax] and Tmax2 were higher for frozen MPI as compared to unfrozen or frozen MPI with cryprotectants. Besides, total enthalpy (AH) for frozen MPI was higher than the other variants. It is likely that the temperatures of phase transition obtained in this study correspond to denaturation temperatures of myosin and actin, although they differ from the temperatures reported for protein isolates (Kijowski, 1989).

180

Conclusion

The use of Na2C03/NaHC03 buffer for the extraction of myofibrillar proteins from MDPM results in an extract with a high dry solids content and good gel forming capability. The use of cryoprotectants is obligatory when freezing of the myofibrillar isolates is required. This aspect has to be further investigated.

References

Baker, R.C. en D.S. Kline, 1984. Acceptability of frankfurters made from mechanically deboned poultry meat as affected by carcass part, condition of meat, and days of storage. Poultry Science 63: 274-278.

Dawson, P.L., B.W. Sheldon, H.R. Ball, 1989. Pilot plant washing procedure to remove fat and color components from mechanically deboned chicken meat. Poultry Sei. 68:749-753

Hernandez, A., R.C. Baker en J.H. Hotchkiss, 1986. Extraction of pigments from mechanically deboned turkey meat. J. Food Sei. 51: 865-867, 872.

Kijowski, J., 1989. Attempts at obtaining the wet concentrate of myofibrils from chicken breast and mechanically deboned poultry and its functional properties. Acta alimentaria polonica 15,4:317-326.

McCready, T.S. and F.E. Cunningham, 1971. Salt soluble proteins of poultry meat. 1. Composition and emulsifying capacity. Poultry Sei. 50:243-248

Lanier, T.C., 1984. Suitability of red hake, Urophycis chuss, and silver hake, Merluccius bilinearis for processing into surimi. Marine fisheries review 46: 43-48.

Lanier, T.C., 1986. Functional properties of surimi. Food Technol. 40: 107-114. Lee, CM., 1984. Surimi process technology. Food Technol. 38: 69-80. Lee, CM., 1986. Surimi manufacturing and fabrication of surimi based products. Food

Technol. 40: 115-124. Lyon, CE. , B.G. Lyon, CE. Davis and W.E. Townsend, 1980. Texture profile analysis

of patties made from mixed and flake-cut mechanically deboned poultry meat. Poultry Science 59: 69-76.

Mackie, I.M., 1982. New approaches in the use of fish proteins. In: Developments in food proteins - 2, pp. 215-262. Hudson, B.J.F. (Ed.). London: Applied Science.

Mast, M.G., T.G. Uijttenboogaart, A.R. Gerrits and A.W. de Vries, 1982. Effect of auger- and press-type mechanical deboning machines on selected characteristics of mechanically deboned poultry. J. Food Sei. 47:1757-1766

McCurdy, S.M., P. Men, P. Fedec and D.F. Wood, 1986. Laboratory and pilot scale recovery of protein from mechanically separated chicken residue. J. Food Sei. 51:742-747,753

181

Ozimek, G., P. Jelen, L. Ozimek, W. Sauer and S.M. McCurdy, 1986. A comparison of mechanically separated and alkali extracted chicken protein for functional and nutritional properties. J. Food Sei. 51:748-753

Scott, D.N., R.W. Poter, G. Kudo, R. Miller, B. Koury, 1988. Effect of freezing and frozen storage of Alaska pollock on the chemical and gel-forming properties of surimi. J. Food Sei. 53,2:353

Wray, T., 1987. Surimi: a protein of the future. Food Manuf. 62, 48-49 Young, L.L., C.E. Lyon, G.K. Searcy and R.L. Wilson, 1987. Influence of sodium

tripolyphosphate and sodium chloride on moisture-retention and textural characteristics of chicken breast meat patties. J. Food Sei. 52,3:571-574.

182

Washing step

MD PM

II

III

IV

water : MDPM 0.5 : 1 5 min blender 1000 rpm

0.1M bicarbonate buffer pH 9.2 2 : 1 60 min slowly mixing

water 2 : 1 + IN HCl adjust to l)pH 5.5; 2)pH 6.0

water 2 : 1 mix 10 min and separate conn, with strainer d> 1.5 - 2 mm

Centrifuge 3000 rpm 10 min.

Supernatant I (fat, soluble proteins)

Centrifuge 3000 rpm 10 min

Supernatant II

Centrifuge 3000 rpm 10 min.

Myofibrillar Protein Isolate

l

Supernatant III

Centrifuge 3000 rpm 10 min.

Supernatant IV

Diagram 1 Extraction method cf MPI from MDPM

183

MPI isolated at

pH5.5 pH6.0

Unfrozen Frozen at - 21 C

Without cryoprotectants

With cryoprotectants

Nr 1

4% sorbitol 4% saccharose

Nr 2

0.5% monosodium glutamate 0.3% tetra sodium pyrophosphate

Diagram 2 Experimental set up of the freezing experiment.

184

Table 1 Characteristics of MDPM used.

Dry solids % pH

Color

MDPM 24.7 6.63 51.0 19.4

Table 2 Yields of the MPI extraction processes (n=6) (%).

Fractions of MDPM

pH

5.5 x s

6.0 x s

Myofibrillar Protein Isolate (MPI)

36.5 6.4

45.0 7.6

P>0.001

Connective Tissue

12.0 1.3

11.5 1.3

n.s.

Fat fraction

10.5 0.9

11.0 1.1

n.s.

Oil fraction

2.0 0.3

1.7 0.3

n.s.

Soluble fraction

39.0 6.7

30.8 6.2

P&0.05

Table 3 Functional properties of MPI, extracted at pH 5.5 and 6.0 (n = 12).

Parameter

pH

5.5 x s

6.0 x s

Dry solids in MPI (%)

30.5 7.1

24.6 6.7

L*

67.1 2.4

61.7 1.9

Color a*

2.7 0.4

5.5 0.8

Emulsion capacity* (%)

269.5 40.4

372.3 70.1

WHC

16.7 3.1

14.0 2.9

* ml oil/g dry solids.

185

Table 4 Heating losses of MPI extraction at pH 5.5 and 6, with or without cryoprotectants (n = 12).

pH Raw Without material cryoprot.

Frozen material Addition of Addition of 4% Sorbitol 0.5% Glut.A-Na 4% Saccharose 0.3% Na-PP

5.5

6.0

X

s

X

s

14.5b

4.7

7.0d

2.1

18.9a

4.5

11.4° 3.6

15.0b

3.9

7.5d

2.7

15.5b

4.1

8.1d

2.4

Table 5 Objective Textural-Analysis.

Unfrozen MPI Frozen MPI (extract pH 6.0) Without Cryoprot. Cryoprot.

pH 5.5 pH 6.0 Cryoprot. nr. 1 nr. 2 Parameter

Max. force during pressure 31.75 44.85 35.85 42.20 41.10

Deformation at max. force 49.2 52.0 47.2 51.2 51.2

Elasticity 13.7 13.6 12.8 13.9 13.4

Shear force 7.96 8.36 3.8 6.04 5.74

186

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187

SESSION M3

METHODS FOR MEASURING QUALITY CRITERIA

189

190

METHODS FOR MEASURING FUNCTIONAL PROPERTIES OF POULTRY MEAT

G.W. Froning

University of Nebraska, Department of Food Science and Technology, Lincoln, NE 68583-0919 USA

Abstract

With the growth of the further processing poultry industry, we have seen many new products in the market place such as sausage products, roasts, meat patties, nuggests, etc. The diet conscious consumer is also demanding more products which are convenient and low in fat, salt, cholesterol and calories. As these new products are developed, the maintenance of desirable functional and sensory properties becomes increasingly important and sometimes more difficult. This presentation will review methods of measuring functional properties as they may relate to desirable properties. Such functional properties as emulsification properties, binding properties, water holding capacity, gelation, juiciness, viscosity and color will be emphasized. The relationship of muscle protein constituents to these functional attributes will also be discussed.

Introduction

Functional properties of poultry meat are important concerns for the food scientist. The organoleptic attributes of foods directly relate to their physical and chemical properties. These physical and chemical properties of proteins are known to affect meat systems in processing, storage, preparation and consumption (Kinsella, 1982). Thus, functional properties are important measures of the consumer's perception of food quality. Kinsella (1982) reviewed functional properties of foods with specific emphasis on food proteins (Table 1,2). Acton et al. (1983) provided an in-depth review of functionality of muscle constituents in processing of comminuted meat products. Their primary emphasis related to water binding (protein-water interaction), fat holding (protein-lipid interaction), emulsification (protein-lipid interaction) and gelation (protein-protein interaction).

With respect to measurement of functional properties of poultry meat products, Froning et al. (1986) reported on recommended procedures. Methods reported included emulsification properties, color, water holding capacity, viscometric properties, tenderness, binding properties and flavor.

191

Emulsification Properties

Model systems of protein extracts and meat homogenates have been routinely utilized to measure emulsification properties of poultry meat systems. Swift et al. (1961) developed the "emulsion capacity" test for meat systems. This procedure involves mixing meat slurries or protein extracts with IM NaCl and a small amount oil, followed by addition of oil at a constant rate and mixing at high speed until the emulsion breaks. Emulsifying capacity is reported as ml of fat emulsified by 2.5 g of meat. Several factors have been shown to affect emulsifying capacity test including the proportion of saline phase, the rate of addition of fat, mixing speed and temperature conditions (Cunningham and Froning, 1972). If these factors are kept constant, this measurement has value in comparing emulsifying capacity of poultry meat under different treatments.

Emulsion stability likely provides a better measure of emulsifying ability in a heated meat system (Townsend et al., 1968). This method involves stuffing emulsions into stoppered polycarbonate syringes and cooking the emulsion to an internal temperature of 68.8°C. The amount of fat, gel-water and solids released per 100g of meat is recorded after centrifugation in a graduated centrifuge tube. Table 3 compares emulsion capacity and emulsion stability tests when studying prerigor and postrigor turkey breast meat (Froning and Neelakantan, 1971).

Fat melting profiles have been studied in meat systems also as an influence on emulsifying ability (Acton et al., 1983). Since fat in poultry meat has a lower melting point as compared to red meats, this factor plays a role in emulsifying capabilities. For example, comminution temperatures of mechanically deboned poultry meat are generally recommended to be lower (12°C) than that of hand-deboned sources (Froning, 1970).

Binding Properties

As more poultry meat has been further processed into rolls, roasts or similar products, binding of meat particles together has become increasingly important. Vadehra and Baker (1970) reviewed the many factors affecting the binding properties of poultry meat in cooked systems. Binding ability is usually measured by tensile strength or sensory panel evaluation (Acton and Dick, (1978). (Acton and Dick 1978) measured tensile strength using a shear press equipped with a tensile cell to determine the effect of added skin. They also used a trained panel which rated binding strength on a 9 point scale with a score of 9 indicating one "extremely good bind" and an "extremely poor bind". Their results are shown in Table 4. Likely, it would be preferable to use both the objective and subjective measurements when determining binding ability.

192

Water Holding Capacity and Juiciness

Water holding properties (WHC) of poultry muscle has been an important consideration with regard to product quality and consumer acceptance. Fennema (1990) provided a comprehensive review on this area in which he defined WHC, free exudate, expressible moisture and water binding potential (Table 5). Fennema categorized methods for measuring WHC as those involving no force, an applied force such as a press or centrifugation and other tests such as NMR (Shanbhag et al., 1970). With respect to poultry muscle, Jauregui et al. (1981) developed a simple and reproducible method using centrifugal force (Table 6). Kauffman et al. (1986) recently described a simple filter paper method which involves placing laboratory grade filter paper against a cut surface of meat and weighing the fluid accumulation.

Juiciness of poultry meat is more difficult to assess since it is likely associated with both fat and moisture relationships in the muscle. Wesley et al. (1958) developed a test for measuring juiciness. This test involved placing a 15 to 25 g sample in a Carver hydraulic press which was preheated to 110°F. Pressure (10,000 lbs per sq. in.) was applied for 10 minutes after which the percent juice expressed is calculated. When measuring juiciness with an objective test such as this Carver method, the researcher should combine it with a sensory evaluation also. Froning et al., 1986 reviewed several references on sensory evaluation.

Gelation

Thermal gelation of muscle proteins particularily myosin is important in further processed poultry meat. Gels impart many desirable attributes including viscoelastic properties, juiciness and texture (Kinsella, 1982). Acton et al. (1983) reviewed gelation.of muscle proteins as related specifically to comminuted products.

Saliba et al. (1987) described a method for measuring gelation. Later Foegeding (1990) adapted this test to measuring gelation properties of raw turkey muscle proteins. True stress and true shear strain were measured using a torsion test. Cooked gels were formed into a dumbbell shape with a minimum diameter of 10 mm. Samples were then twisted to failure of 2.5 rpm using a torsion fixture attached to a Brookfield 5XHB TD viscometer. True shear stress and strain were calculated. Table 7 shows the relationship of protein concentration to gelation properties.

193

Viscosity

Acton et al. (1983) reviewed various aspects of viscosity measurement and some important considerations for meat systems. Flow properties of raw meat batters prior to heat processing have been studied to relate with protein functionality. Since meat is a discontinuous mixture, measurement of viscosity becomes more complicated. Hamm (1975) indicated that sausage batters follow pseudoplastic flow behavior.

Viscosity is defined as the ratio of shear stress to shear rate. Viscosity of pseudoplastic materials (Non-Newtonian) show a dependency upon the rate of shear applied (Acton et al., 1983). Thus, it is inappropriate to determine viscosity using a single shear rate. Acton et al. (1983) indicated that measurement of relative or apparent viscosity might be utilized for comparative purposes as long as there are no major material differences within the samples evaluated. Here again, he explained that entirely different results may be possible at different shear rates.

Color

Color is another important consideration with relation to consumer acceptance. With the advent of more further processed poultry products abnormal pink color problems have become particularly troublesome to the poultry processing industry. Meat color is normally determined using reflectance instrumentation such as the Gardner or Hunter Color Difference Meter (Lyon et al., 1976; Froning et al., 1968). Color difference values L, aL and bL values are commonly reported. L values denote lightness, aL values indicate degree of redness (increasing positive aL values are associated with increasing redness) and bL values are an expression of the degree of yellowness (increasing positive bL values indicate more yellowness). Several factors may influence the accuracy of color measurements (Table 8). Spectrophotometric reflectance measured in the visible region (400-700 mm) can also provide utilized effectively particularly when ascertaining the degree of doneness of cooked meat (Froning et aL, 1968).

References

Acton, J.C., Ziegler, G.R. and Bürge, D.L., 1983. Functionality of muscle constituents in the processing of comminuted meat products. Editor Thomas E. Furia Critical Reviews in Food Science and Nutrition CRC Press Inc. Boca Raton, Florida.

Acton, J.C. and R.L. Dick, 1978. Effect of skin content on some properties of poultry meat loaves. Poultry Sei. 57:1255-1259.

194

Cunningham, F.E. and Froning, G.W., 1972. A review of factors affecting emulsifying characteristics of poultry meat. Poultry Sei. 51:1714-1720.

Fennema, O.R., 1990. Comparative water holding properties of various muscle foods. J. of Muscle Foods 1:363-381.

Foegeding, E.A., 1990. Development of a test to predict gelation properties of raw turkey muscle proteins. J. of Food Sei. 55:932-941.

Froning, G.W. and Neelakantan, 1971. Emulsifying characteristics of pre-rigor and postrigor poultry muscle. Poultry Sei. 50:839-845.

Froning, G.W., 1970. Poultry meat sources and emulsifying characteristics as related to processing variables. Poultry Sei. 49:1625-1631.

Froning, G.W., Acton, J.C., Ball, H.R., Brekke, C.J., Hasiak, R.J. and Cox, N.A., 1986. Recommended methods for the analysis of eggs and poultry meat. An annotated bibliography. North Central Regional Research Bulletin No. 307.

Froning, G.W., Hargus, G. and Härtung, T.E., 1968. Color and texture of ground turkey meat products as affected by dried egg white solids. Poultry Sei. 47:1187-1191.

Hamm, R., 1975. On the rheology of minced meat. J. Texture Stud. 6:281-296. Kauffman, R.G., Eikelenboom, G., van der Wal, P.G., Merkus, G. and Zaar, M., 1986.

The use of filter paper to estimate drip loss of porcine musculature. Meat Science 18:191-200.

Kinsella, F.H., 1982. Relationships between structure and functional properties of food proteins. In Food Proteins. Editors Fox, P.F. and Condon, J.J. Applied Science Publishers London and New York.

Lyon, CE. , Townsend, W.E. and Wilson, R.L., 1976. Objective color values of non-frozen and frozen broiler breasts and thighs. Poultry Sei. 55:1307-1312.

Saliba, D.A., Foegeding, E.A. and Hamann, D.D., 1987. Structural failure and nondestructive rheologocial analyses of frankfurter batters: Effects of heating rates and sugars. J. of Textural Studies 18:241-259.

Shanbhag, S., Steinberg, M.P. and Nelson, A.I., 1970. Bound water defined and determined at constant temperature by wide-line NMR. J. of Food Sei. 35:612-615.

Swift, C.E., Lockett, C. and Fryar, 1961. Comminuted meat emulsions - the capacity of meats for emulsifying fats. Food Technol. 15:468-473.

Vadehra, D.V. and Baker, R.C., 1970. The mechanism of heat iniatiated binding of poultry meat. Food Technol. 24:42-55.

Wesley, R.L., Korslund, HJ. , and Stadelman, W.J., 1958. The effect of hormonization on juiciness and tenderness of chicken meat. Poultry Sei. 37:1443-1446.

195

Table 1 Typical functional properties performed by functional proteins in heat systems (Kinsella, 1982).

Functional property

Water absorption and binding

Viscosity

Gelation

Cohesion-adhesion

Elasticity

Emulsification

Fat absorption

Flavour-binding

Mode of action

Hydrogen bonding of water; Entrapment of water (no drip)

Thickening; Water binding

Protein matrix formation and setting

Protein acts as adhesive material

Disulphide links in gels

Formation and stabilisation of fat emulsions

Binding of free fat

Adsorption, entrapment, release

Meat system

Meat, Sausages

Soups, Gravies Meat Batters

Meats

Meat, Sausages

Meats

Sausages, Bologna

Meats, Sausages

196

Table 2 Functions of ingredient protein in meat-based products (Kinsella, 1982).

Improves uniform emulsion formation and stabilisation

Gelation improves firmness, pliability and texture

Facilitates cleaner, smoother slicing

Reduces cooking shrinkage and drip by entrapping/binding fats and water

Prevents fat separation

Enhances binding of meat particles without stickiness

Improves moisture-holding and mouthfeel

May impart antioxidant effects

Table 3 The effect of post- and prerigor turkey breast muscle on emulsifying capacity, emulsion stability and tensile strength of prepared emulsions (Froning and Neelakantan, 1971)'.

Age of bird at slaughter

Weeks

22

24

26

State of rigor

Pre Post

Pre Post

Pre Post

Emulsifying capacity per 2.5 g. meat

ml.

145a 133d

161b 130d

185c 137d

Gel water per 100 g. emulsion

ml.

9.73a 13.45c

8.94a 10.58d

4.46b 9.70c

Fat per 100 g. emulsion

ml.

0.44a 0.60c

0.37a 0.61c

0.06b 0.57c

Solids per 100 g. emulsion

0.58a 0.53a

0.45a 0.27b

0.42a 0.21b

'Means not having the same subscripts in the same column are significantly different at the .05 level of probability.

197

Table 4 Effect of skin content on binding and tensile strengths of cooked meat loaves (Acton and Dick, 1978).

Percent skin

0 20 33 42 50

Binding strength11

6.3a

5.6a

8.1° 7.4bc

6.4ab

Tensile strength (kg/cm2)

. 1347ab

. 1227a

.1401bc

.1458bc

.1487°

a,b,cAny two means within a column having the same letter are not significantly different (P>.05). dBinding strength scale: 9 = extremely good bind; 1 = extremely poor bind.

Table 5 Definitions associated with water holding capacity (Fennema 1990).

Water Holding Capacity (WHC): A general term referring to the ability of a defined sample to retain intrinsic or extrinsic fluids under specified conditions.

Free Exudate (or Free Drip or Thaw Exudate): Amount of intrinsic fluid that exudes from a defined sample under specified conditons.

Expressible Moisture (EM): Amount of intrinsic fluid expressed from a defined sample by the application of a specified external force under specified conditions.

Water-Binding Potential (WBP): Amount of fluid expressed from a defined sample following the addition of an aqueous fluid and the subsequent application of a specified external force under specified conditions.

198

Table 6 Comparative water holding capacities of fresh fish, chicken and beef (Jauregui etal., 1981).

Sample type

Beef, sirloin tip

Chicken light dark

Trout, rainbow

Initial water content (%)

75.8

77.1 75.9

76.9

Expressible moisture" (%)

38.2 ± 1.7

22.9 ± 1.2 21.2 ± 1.7

39.0 + 1.9

"1.5 g ground samples, centrifuged at 30,900 x G at 2°C

Table 7 Effects of protein concentration on texture and water-holding ability of turkey breast meat (Foegeding, 1990).

Protein cone. (%)

Experiment 1 17 14 11

Experiment 2 13 10 7

Shear stress at failure (kPa)

25.5a

11.6b

4.8e

14.2a

4.8b

_e

Shear strain at failure (m/m)

1.22a

1.17b

1.16b

1.19a

1.07b

-

Cooking yield (%)

95.7a

91.5b

81.3e

88.5a

76.4b

49.0e

Held-water (g water/g protein)

_d

--

1.45" 1.40a

1.29a

Experiment 1 was conducted with one pooled source of meat and the values represent the average of three gel preparations. Experiment 2 was conducted with three lots of meat. There were three gel preparations for each meat source so the values are the means of 9 gel preparations.

acMean values within columns of each experiment with different superscripts are significantly different (P<0.05). dHeld-water was not determined in experiment 1. The 7% protein gels were too frail for rheological testing.

199

Table 8 Factors affecting meat color measurement.

1. The surface of the meat should be smooth and of uniform thickness.

2. Measurements should be made on the same muscle for comparative purposes (eg breast muscle).

3. Measurements should be made on freshly sliced samples.

4. The reference plate used should be close to the color of the meat.

200

FUNCTIONAL PROPERTIES OF POULTRY MEAT, POSSIBILITIES FOR MEASURING WATER-BINDING CAPACITY

S.H.V. Erdész1, S. Erdész1 and F.J. Jankóné2

1 Association of Poultry Producers, Akadémia u. 1-3, Budapest, Hungary 2 Academic Faculty of University of Horticulture and Food Industry, Moszkva krt.

7, Szeged, Hungary

Abstract

Water holding and binding capacity play an important role among functional properties of (poultry) meat. Several methods are available for determination of the water binding eg. pressure, capillary and centrifugal methods. Two other different methods are possible: based upon glycerol extraction followed by determination of the refractive index of the extract and determination of humidity of the air space above the sample. All methods are evaluated.

Introduction

Functional properties of meat are crucial in the further processing. Functional properties are the totality of those features which present valuable information on changes during processing or those features which help, make possible or render difficult meat processing. The properties are primarily related to change of state of water and fat. Some of these properties are: - water absorption - water holding - bound water - emulsion making - emulsion capacity - stabilization of emulsion - emulsifying activity All these properties play an important role in relation to sensory properties which affect quality of both raw material and finished product. This contribution deals with water absorbing ability and the possible methods of determination.

201

Water is bound in meat - so in poultry meat - in different ways. One part of water is bound tight, other part is bound weak. The weakly bound water is most responsible for water binding properties of meat. Water binding or - absorbing capacity is the property of muscle tissue or meat - protein to hold its own water and added water. This water is not released through smaller mechanical effects, eg. pressure etc. The water binding properties can be affected by various factors like time, heat etc.

Possibilities for measuring water-binding capacity

A method of determination of the water-binding capacity consists of two parts. In the first stage quantity of water is added to the meat sample in different ways. In the second stage this sample is submitted to a treatment and water release is measured. The measurement at this second stage, the treatment and consequent water release, is reliable if it fits the actually added and bound water quantity. It is a method for determination of lightly bound or extraneous water. Several methods for determining absorbed water exist. Some of them are: 1. GRAU-HAMM method

The method is based on pressing a sample (muscle tissue, meat pulp, etc.) and measuring the quantity of released liquid by planimetry or weighing.

2. HOFFMANN method This method is based on capillar-volumetry, by a suction effect of a porous gypsum body. Weight on this body may be between 50-2000 g.

3. BOUTON method This method uses a standardized centrifugal power to separate water. The quantity is an indication of weakly bound water.

Basic principle of these methods is measuring released water after a pressure treatment on sample. Two further methods must be mentioned which use a different basic principle. These are: 4. Extraction by glycerine

Samples are extracted by pure glycerine for a certain time at a certain temperature. Mixture is strained and water content of this glycerine-water solution is determined.

5. Sample is held in a closed space at a certain temperature. The relative humidity or partial vapor pressure is continuously measured.

202

Next the mentioned methods are evaluated.

1. Grau and Hamm method. The filter paper is stored during at least 24 hours in an exsiccator. A sample of 200-300 mg of meat or meat pulp is placed on a filter paper. The paper sample is put between glass plates and loaded by 1000 g for 5 minutes after which the quantity of released liquid is determined by measuring the area or, by weighing. Depending on measuring method the waterbinding capacity is obtained as follows:

Water binding planimetered area (mm2) capacity (mm2/mg) =

muscle tissue (g)

Water binding weight of (filter paper + water) - weight of filter paper capacity (%) =

weight of measured sample

2. Hoffmann method. Measuring the water binding by this method is based on a suction effect of a porous gypsum body with dimensions 2.5 cm o and about 1 cm height. This body is set in a mounting and connected air-thight to a vertical tube of glass which is "U" shaped and filled with coloured liquid. The piece of meat to be measured is placed on the surface of a gypsum body. Lightly bound water present in sample will push away the air from this gypsum body. This air-volume theoretically corresponds to the volume of meat-liquid and causes elevation of coloured liquid in the tube. Reading may be conducted both on micro graduated scale and on a simplified three-coloured graduation in which the range 0-50 is green meaning good water binding while the red range 70-115 means bad binding. The yellow coloured intermediate zone is in the middle. This method is only an approximation. Benefits are: - very simple - weighing of sample is not necessary - quickly obtained results - good reproducibility

Evaluation of result: The value of the capillary volumeter graduation = lightly bound water (mg). For obtaining reproducible results following points are important: - no significant variation in results are obtained in relation of thickness of samples,

0.25-1.75 cm is suggested; - the result should read from the scale after 2 minutes; - some authors uses expedient pressure load ranging to 1000 g to obtain higher

values, however, experience shows that suction effect of gypsum capillary has only a minor role.

203

3. Establish water binding capacity by centrifuge. About 2 g of sample, weighed with analytical precision is put in a centrifuge tube and centrifuged at high speed for 30 minutes. After centrifuging the sample is taken off from meat liquid pressed-out, dried with filter paper and weighed. After this the dry solids content of the sample is determined.

Evaluation of result:

WHC % = released water quantity (g)

1 total water content (g)

WHC = Water Holding Capacity

Some results of comparing mentioned methods are presented here:

Ultra-X Capillar volumetry (X)

Measuring time 60 sec

Measuring time 120 sec

Centrifugal method Ultra-X (Y)

r = 0.77xx

log y = 3.88-2.59X

r = 0.82xx

log y = 4.31-2.92X

Pressure method Ultra-X (Y)

r = 0.56xxx

y = -70.59+15.01X

r = 0.62xxx

y = 113.86+24.25X

Some reservations have to be made for all methods mentioned above. The obtained results differ from actual lightly bound water content, specially from picked up water. In some cases methods provide less, in other cases bigger values of picked up and bound water than what is actually present. For determining of extraneous water content there are some other methods too in the area of quality control. For instant the German and Danish method which are used in the European Community determine water content of poultry based upon the physiological relation of water and protein. Same problems related to these methods exist and, besides these problems, these methods are complicated and can very hard be put into practice. The results sometimes differ from actual extraneous water content.

Glycerol - extraction method It is well known that glycerol mixes excellently with water and because of it affinity to water it is very suitable for migration of water from solid phases to glycerol. In first stage of extraction solely the lightly bound water will be extracted totally by glycerol, if adequate extraction time choosed. After the extraction the sample should be separated from the glycerol-water blend and its water content determined. This is

204

equal to the quantity picked up and lightly bound water. For adequate precision a relatively big amount of sample should be used. For the examination a accurately weighed 50 g sample is put into Erlenmeyer retort and 60 ml pure glycerol is added. This blend is shaked for 12 minutes at temperature 22 °C and after that filtered through a filter paper. Refractivity of filtrate is determined using a ABBE refractometer with sodium spectral lamp. Previously a calibration graph of the glycerol content and the refractivity of the glycerol-water mixture has to be made. Based on this the extracted water can be calculated from the refractivity data. Referring this quantity to weight of the given sample, the final result is calculated. This method is very simple, quick, indulgent and it can be repeated well.

Determination of bound water by determination of relative humidity of air space. Sample should be put in an instrument specially made for this purpose. The temperature of the air space should be 68°C and controlled by a thermostat. Relative humidity from first moment should be measured continuously by a sensor. According to data from literature there is tight correlation between final relative humidity developed in air space and water activity. Humidity of the air space rises steeply but after this the slope decreases becomes more and more flat. The line shows a well determinable point of inflexion. According to our studies time period from beginning of measure to reaching of inflexion shows very good correlation with picked up water quantity. According to our measurements, quantity of bound water, determined this way, approaches best actually added water quantity.

The last two methods are only possibilities, which in other fields work reliable. Use for purposes mentioned above need further research which seems to be worthwhile.

References

Grau, R., 1960. Fleisch und Fleischwaren. A.W. Hayn's Erben Verlag Berlin. Grau-Hamm, 1954. Brühwurst qualität und Bestimmung der Wasserbindung. Fleisch und

Fleischwirtschaft 6, 36. Hamm, R., 1960. Biochemmistry of meat hydration. Advances in food research. 10, 336. Husipari Kézikönyv, 1973. Hungarian handbook of meat industry. Mezogazdasâgi

könyvkiadó Budapest. Mc Waters, K. and Cherry, J.P., 1981. Protein functionality in foods. Washington DC

217.

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206

REAL-TIME ULTRASONIC SCANNING FOR THE ESTIMATION OF BREAST MUSCLE WEIGHT IN CHICKEN

M.A. Grashorn and P. Komender1

470 Dept. of Poultry Science, University of Hohenheim Garbenstr. 17, 7000 Stuttgart 70, Germany, 'institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzebiec, 05-551 Mrokow, Poland

Abstract

The main criterion in broiler meat production is to produce carcasses with a high proportion of meat, especially of breast meat and leg meat. Using a real-time ultrasonic scanner allows to estimate these proportions and weights. An experiment with 265 male broilers was started to estimate correlations between the ultrasonically measured breast thickness and the weights and percentages of breast meat and valuable parts. The correlations between the thickness of breast meat and the weight of breast meat and between the thickness of breast and the weight of valuable parts was 0.64 and 0.55, respectively. The multiple regression approach led to a multiple correlation of 0.89 by using the slaughter weight as an additional trait. The multiple correlation to the weight of valuable parts was 0.97. In both cases the partial correlation coefficient for the breast thickness was low. It was concluded that estimating the area or the volume of breast muscle may increase the correlations.

Introduction

The main objective in meat production is to produce carcasses with a high proportion of meat. The improvement of meatiness is done by breeding strategies. For the genetic selection parameters are used which are highly correlated to meatiness, for example the proportions of the valuable parts breast and thighs achieved by dissection of the carcasses or the measurements of the length, the width and the angle of the breast. Another way is to measure the thickness of the breast by inserting a needle or by using an ultrasonic equipment. The traditional ultrasonic equipment was a one-channel device which revealed a graph with peaks at the transitions from one tissue to the other. It was quite difficult to interpret the results and the received value described only the thickness of the breast depending on where the scanner was put on the surface. Therefore, the correlation between the ultrasonically measured breast thickness and the breast weight or percentage of breast was not superior to the other supporting parameters (Table 1).

207

Table 1 Correlations between amount of breast meat and some other supporting parameters (Scholtyssek, 1987).

Measurements

breast angle length width thickness

(ultrasonic) (needle)

LBx WB LB x WB x THUS

(AB) (LB) (WB)

(THUS) (THN)

Living

0.45 0.50 0.54

0.52 -

0.68 0.84

Slaughtered

0.50 0.53 0.58

0.59 0.60

0.72 0.90

Higher correlations may be achieved by combining different parameters. But this means that two or three measurements have to be done to get a good estimate for the breast meat.

Meanwhile, the evolution in computer technics allowed for the development of a new type of ultrasonic equipment which may give the estimate of the area of breast muscle at a fixed point besides the thickness of breast muscle. Former investigations have revealed favourable correlations (0.6 - 0.7) between the area of breast muscle measured by living and slaughtered birds and the weight of the breast meat (Komender and Grashorn, 1990a,b).

In this paper the results of using the real-time ultrasonic scanner for estimating the weight and the percentage of breast meat and thighs by measuring the carcasses will be described. The intention for the investigation was to test whether this system will be able to give reliable values for the percentage of valuable parts which may be used for grading the carcasses according to their meat content in the slaughter process.

Materials and Methods

For this experiment 265 male broilers of different genetic background were used. The broilers were reared on deep litter for 41 days under standard conditions. The birds were fed a diet with 230 g crude protein and 14 MJ metabolizable energy/kg ad libitum. At the end of the fattening period live weights were recorded. After evisceration carcasses were

208

weighed and air-cooled. The cooled carcasses were weighed again and the measurement of the thickness of breast muscle was done by ultrasonic device. Afterwards the carcasses were dissected in the wings, legs and breast.

For ultrasonic measurements the Echoscan-system of 'animal scanning systems', Stuttgart - Germany, was used. The system consisted of the scanner, a digitalizing card and an AT personal computer with special video-processing software. The scanner was a linear-array transducer using an ultrasonic frequency of 3.5 megahertz with a water pad for improving the contact with the skin.

The measurement was conducted by putting the scanner on the breast of the bird in an angle of 90° to the axis of the body. Starting caudal the scanner was moved on this axis cranial till the sternum and the ribs were visible as one line on the screen. The picture was stored for further analysis.

The pictures were analysed afterwards by using the video processing software. The program first determines the centre of the breast and then fixes the marks of the breast in the range mean +/- a (a = about 3 cm) (Figure 1). The angles at the marks Bj and B2 and the thickness of muscle at these points were calculated to allow for a test of symmetry of the breast. By doing this the deformation of the breast is considered which may bias the estimation of the area of the breast. This is a requirement for an automatic analysis of the pictures. The system of automatic analysis may be used in the slaughter process for the very short time needed. The whole procedure takes two to three seconds per carcass.

In this experiment the average of the two measurements of breast thickness (b1; b ^ were used for statistical analysis. The results from estimating the area of breast muscle (cut) are in preparation.

Results

The values for the different traits for carcass quality are summarized in Table 2. The mean live weight was 1908 g and the mean slaughter weight was 1240 g resulting in a slaughter yield (without head, feet and giblets) of about 65 %. The coefficients of variation were rather high except for slaughter yield. The weights and the percentages of valuable parts were in a common range. The high variations for the weight and the percentages of the breast meat were due to the inhomogeneous material and the technique of dissection. The estimate of breast muscle thickness was 25.6 mm with a rather high coefficient of variation.

209

Table 2 Live weight and slaughter traits (N = 261).

Mean coefficient of variation

live weight (g) 1908 11.0 slaughter weight (cold) 1240 12.5 slaughter yield (%) 65.4 3.1

weight of breast meat (g) 221 17.1 weight of legs (g) 439 12.8 weight of wings (g) 163 10.0 weight of valuable parts (g) 661 13.4

breast meat in % of carcass 17.7 7.8 legs in % of carcass 36.0 3.6 wings in % of carcass 13.7 5.6 valuable parts in % of care. 53.2 3.5

thickness of breast m. (mm) 25.6 8.6

The correlations between traits were different depending on the traits compared (Table 3). Close correlations were observed for the weights of valuable parts and the slaughter weight. The correlation between breast meat weight and the percentage of the breast meat was not as high as expected which may be due to the dissection. The correlations between the percentage of breast meat and the other traits were low. The relations between the ultrasonic breast thickness and the carcass traits were in a middle to high range. The highest correlation (r = 0.64) was estimated for the weight of breast meat.

Table 3 Correlations between slaughter traits and breast muscle thickness measured ultrasonically.

2

1 slaughter weight 0.90 2 weight of wings 1.00 3 weight of thighs 4 weight of breast meat 5 percentage of breast 6 weight of valuable parts 7 breast thickness

3

0.96 0.89 1.00

4

0.89 0.74 0.80 1.00

5

0.34 0.18 0.22 0.72 1.00

6

0.97 0.88 0.97 0.92 0.43 1.00

7

0.53 0.44 0.46 0.64 0.51 0.55 1.00

210

The multiple regression approach using slaughter weight in addition to breast thickness to estimate breast meat weight led to a better coefficient of determination (r2 = 79.2 %). The coefficient of multiple correlations was 0.89 (Table 4) and this result was better than in former experiments. Nevertheless, including the slaughter weight was more informative than including breast thickness which is obvious in the partial correlation coefficient of 0.20.

Table 4 Multiple regression between breast weight, thickness of breast and slaughter weight. :

Coefficient of regr.

error of coef.

F-value partial corr.

constant slaughter weight breast thickness

19.5 0.182 4.1

12.7 0.008 0.53

74.8 509.6 51.1

*** ### ***

0.87 0.20

N = 261; multiple corr. = 0.89; *** : P ä 0.1 %

The multiple correlation to the percentage of breast meat was quite poor (r = 0.50), however, which may be due to the use of the slaughter weight twice in the calculations.

The results for estimating the weight of valuable parts by slaughter weight and breast thickness are summarized in Table 5. The correlation between slaughter weight and valuable parts was very high, therefore, the additional information of the breast thickness was poor. The estimated partial correlation was 0.04 although the coefficient of regression was significant. The multiple correlation between the percentage of valuable parts, slaughter weight and breast thickness was lower (r = 0.31) than between the weight of breast, slaughter weight and breast thickness.

Table 5 Multiple regression between the weight of valuable parts, slaughter weight and breast thickness.

coefficient of regr.

error of coef.

F-value partial corr.

constant slaughter weight breast thickness

76.7 0.551 2.1

15.2 0.008 0.68

25.5 3240.0

9.3

*** *** **

0.97 0.04

N =261 ; multiple corr. = 0.97; *** : P <; 0.1 %; ** : P £ 1 %

111

Altogether, the experiment revealed quite good correlations between the ultrasonically measured breast thickness and the weight of the breast was well as the weight of valuable parts. Nevertheless, combining the breast thickness with the slaughter weight to a multiple correlation gives a good evidence for estimating breast weight. The same applies for the weight of valuable parts. Improving the technique of the ultrasonic equipment and estimating the area or the volume of the breast muscle may lead to better correlations to the desired traits. These calculations are in preparation.

References

Komender, P. and Grashorn, M.A., 1990a. Ultrasonic measurement of breast meat. Poultry International 29, 36-40.

Komender, P. and Grashorn, M.A., 1990b. Automatische Bestimmung des Fleischanteils beim Broiler: Zukunftsmusik für Züchter und Vermarkter. DGS 42, 1139-1142.

Scholtyssek, S., 1990. Geflügelprodukte. In S. Scholtyssek 'Geflügel', Eugen Ulmer Verlag, Stuttgart, 81 - 137.

212

Figure 1 Schematic description of measuring the thickness and the area of breast muscle. A = centre of the breast B!,B2 = left and right border a!,a2 = distances between the borders and the centre of the breast (about 3

cm) b!,b2 = thickness of muscle left and right MF = are of muscle a = angle of breast ß = angle of comparison

213

214

NUTRITIONAL AND GENETIC EFFECTS ON CARCASS FAT IN BROILERS, WITH EMPHASIS OF NIRS FOR QUALITY CONTROL

G. Huyghebaert1, J.L. De Boever2 and G. De Groote1

1 Rijksstation voor Kleinveeteelt (C.L.O.-Gent), Merelbeke, Belgium 2 Rijksstation voor Veevoeding (C.L.O.-Gent), Melle, Belgium

Abstract

A multifactorial experiment (treatment x sex) was designed to investigate the effect of selective breeding (lean strain vs. commercial strain) as well as dietary manipulations (nutrient density, early feed restriction, ...) on the fat content in the main edible parts of broilers slaughtered at 45 and 52 days of age, with emphasis of NIRS for quality (fat) control. Fat content of the edible parts was affected to a variable degree by genotype, sex, age and dietary manipulations. Prediction accuracy with NIRS depended on the kind of carcass part and was relatively low (esp. for drumsticks and thighs). In spite of the non-homogenecity of the meat samples, the results of this study indicated the potential use of NIRS for chicken carcass analysis.

Introduction

Carcass and meat quality are of increasing importance. One of the major concerns in the broiler industry is carcass fatness, since there is little doubt that the fat content of broilers has increased in recent years. Whatever the cause of this fat increase, it is clear that genetic selection against fatness offers an effective way of solving the problem on a longterm schedule (Leenstra, 1987). Until such genetic change has been brought in practice, nutritional factors can be manipulated to some extent to modify body composition: protein-to-energy ratio, phase feeding for energy and/or protein, (early severe) feed restriction (Fisher and Wilson, 1974; Plavnik and Hurwitz, 1985; Huyghebaert et al., 1989). Interactions with slaughter age as well as sexual dimorphism may thereby not be overlooked.

Nutritional research in poultry often requires chemical carcass analysis for assessing the nutritive effect of dietary manipulations. Conventional analyses for fat are time-consuming, laborious, need toxic chemicals and produce polluting wastes.

215

During the last decade, near infrared reflectance spectroscopy (NIRS)-analysis has become a full-fledged analytical tool: NIRS is quick, allows several constituents of a sample to be analysed simultaneously and is friendly to the environment. Recently, NIRS-analysis has been used to analyse poultry carcasses (Steverink et al., 1988; Valdes et al., 1989). The objectives of this study were: 1. to evaluate the effects of some dietary manipulations, relative to those of genotype, on the fat content in the main edible parts of male as well as female broilers, slaughtered at 45 & 52 days of age and 2. to indentify wavelengths in the NIR spectra related to the fat content and to develop and evaluate NIRS-calibrations for the main edible parts.

Materials and Methods

For this experiment, 900 male and 900 female day old broiler chickens were randomly allotted to 60 floor pens, under conventional housing conditions. This experiment was designed two-factorially: 8 treatments (Table 1) x 2 sexes. The different treatments consisted of: 1. lean type broilers (selected for feed eff.), 2. phase feeding for protein ( + amino acids), 3. no phase feeding, 4. cfr. treatment 3 (but with extra supplementation with L-lysine & DL-methionine), 5. phase feeding for nutrient density (Low energy (LE) at Metabolizable energy (MEn) = 12.54 MJ/kg; High energy (HE) at MEn = 13.17 MJ/kg), 6. phase feeding for MEn & protein (amino acids), treatments 7 & 8 early (6-11 days) feed restriction at resp. high and low nutrient density (Huyghebaert et al., 1990).

At 45 and 52 days of age, resp. 3 birds per pen were slaughtered in a local slaughter house. The cooled, eviscerated carcasses have been cut into more edible parts and less edible parts. The fat content was determined in duplo by Soxhlet extraction with petroleumether on pooled (from 3 broilers per pen), mixed, lyophilized samples from the 3 main edible parts: breast meat (=BM), deboned (anatomical) thigh (with skin: = TM) and deboned drumstick (with skin: = DM). The fat content is expressed as a percentage of pooled fresh weight. All results were subjected to a two-way factorial analysis of variance: 8 treatments (= A) x 2 sexes (= B), each with replications (4 or 3) (Snedecor and Cochran, 1967). Factorial means were compared with each other by means of Duncan's multiple range test (Duncan, 1955).

NIRS-analysis was carried out with a Technicon-500 monochromator, scanning the 1100-2500 nm region with 4 nm-steps, interfaced with a IBM-AT-PC and using IDAS-software (De Boever, 1990). The meat samples were loaded in closed cups and packed three times as the material appeared very heterogeneous. Approximately the same number (=n) of samples (of BM, DM & TM resp.) were used for calibration and validation sets. The samples (of which spectra of 3 packings were averaged) in the calibration sets were selected to represent the range of values encountered for the fat parameter. The prediction equations were tested (on 3 individual packings in order to calculate repeatability, R:

216

mean SD of 3 replicates) with samples drawn from the same populations, but not used in the calibration sets (independent validation).

Results and Discussion

The main results are summarized in Tables 2-3 and Figure 1. Fat content of the edible parts was affected to a variable degree by genotype, dietary manipulations, sex and age: the magnitude however depending on the kind of carcass component. Selective breeding (e.g. for feed efficiency) is very effective to reduce the fat deposition. The influence of dietary manipulations, except for early feed restriction (treatment 7 & 8), on fat deposition was rather limited, moreover diminishing with age. The fat content of the edible parts increased with age and was higher in females than in males. The increase in fatness with age was more pronounced in the female broilers than in the male broilers. Moreover, the sex-linked difference in fat content was more pronounced in fat-rich retail cuts (TM > DM > BM). Especially in females, a major increase in the subcutaneous fat depots of the thigh has been observed from 45 to 52 days of age. This fat depot represents a waste product to the consumer since it results in extra cooking losses.

Table 1 Experimental design.

Treatment

1 2 3 4 5 6 7 8

Type of broiler

COVP (feed eff.) ROSS (growth) ROSS ROSS ROSS ROSS ROSS(*) ROSS(*)

Type of diet 0-2 Id

HE-NAA HE-HAA HE-NAA HE-N(LSA)AA LE-NAA LE-LAA HE-NAA LE-NAA

21-45 (&52d)

HE-NAA HE-LAA HE-NAA HE-N(LSA)AA HE-NAA HE-NAA HE-NAA HE-NAA

Number of replications (for each sex)

4 4 4 4 4 4 3 3

(*) early undernutrition from 6 to 11 days of age.

217

Table 2 The fat content (%) of edible parts (at 45 & 52 days).

Analysis of variance F-values

* treatments (A) * sex (B) * A x B

Factorial means - treatment 1 2 3 4 5 6 7 8

S.E.(n=8/6)

- sex male female

S.E.(n=30)

BM 45 d

1.18 2.97 0.37

1.96a 2.28a 2.14a 2.09a 2.11a 2.06a 2.26a 2.17a

0.14/0.17

2.03a 2.23a

0.07

52 d

7.61*** 5.69(*) 0.02

2.58e 3.58ab 3.34abc 3.63a 3.19abcd 3.06bcde 2.73de 3.00cde

0.13/0.15

3.04a 3.27a

0.07

DM 45 d

449***

3.04(*) 0.05

5.92c 7.48ab 7.60a 7.14ab 6.52abc 6.38bc 6.39bc 6.53abc

0.28/0.32

6.57a 6.95a

0.14

52 d

6.92*** 25.70*** 0.39

6.34c 8.00ab 8.48a 8.12ab 7.83ab 7.94ab 7.34bc 7.16bc

0.25/0.29

7.21b 8.15a

0.13

TM 45 d

23.07*** 15.13*** 0.13

11.82c 19.26ab 18.78ab 19.30ab 19.64a 18.41ab 17.03b 17.90ab

0.53/0.61

17.03b 18.54a

0.27

52 d

28.06*** 90.44***

3.11*

13.66d 22.41a 21.64ab 21.40ab 20.48ab 20.52ab 18.15c 19.79bc

0.52/0.60

18.00b 21.62a

0.27

* F-values with ***, **, * = significantly different resp. at P: 0.001, 0.01 and 0.05. * S.E. = pooled standard error (n = number of observations = 8, 6 or 30). * Means with the same letter are not significantly different from each other at P: 0.05.

The chemically determined fat content varied from 2 to 14 % for breast meat, from 15 to 29 % for drumstick and from 30 to 58 % for thigh. The wavelengths selected in the calibration are given in Table 3. These "so-called" fat specific wavelengths (selected by means of combination search) fell in the lower NIR-region (1100-1600 nm), but depended on the kind of poultry meat (although a similar fatty acid profile). Prediction accuracy decreased with increasing fat content of the meat-type: from breast meat over drumstick to thigh. Compared with the lab-fat determination, NIRS-repeatability was relatively low, especially for drumstick and thigh. On the other hand the biases (= differences between lab-means and NIRS-means) were relatively low: -0.08, -0.12 and -0.27 for resp. BM, DM and TM. These results are particularly interesting when the physical characteristics of the lyophilized poultry carcass parts are taken into account: clear differences in particle size, particle uniformity as well as packing density into the holding cup. Consequently, the particle homogeneity (for fat-rich samples !) should be improved. Nevertheless, the results of this study confirm previous suggestions on the potential use of NIRS for chicken carcass analysis.

218

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References

De Boever, J.L., Huyghebaert, G., Boucqué, C.V. and De Groote, G., 1990. Prediction of fat content in broiler meat by NIRS. The 3th Int. Conf. NIR-spectroscopy (25-29 June, Brussels).

Fisher, C. and Wilson, B.J., 1974. Response to dietary energy concentration by growing chickens. In "Energy Requirements of Poultry" (T.R. Morris and B.M. Freeman, Eds.), pp 151-184. Published by B.P.S. Ltd, Edingburgh.

Huyghebaert, G., Scheele, C.W., De Munter, G. and De Groote, G., 1989. The utilization of the metabolizable energy from carbohydrates and fats by broiler chicks. In "Proceedings of the 11th Symposium on Energy Metabolism of farm animals (Lunteren, The Netherlands): 9-12.

Huyghebaert, G., De Munter, G., Leenstra, F.R. and De Groote, G., 1991. The effects of dietary factors and of genotype on performances and carcass quality of broiler chickens. Arch. f. Geflügelk. (in press).

Leenstra, F.R.,1987. Ph. D. "Fat deposition in a broiler sire strain", COVP uitgave No. 462.

Steverink, A.T.G., Steunenberg, H., Frankhuizen, R. and Tusveld, M., 1988. Toepassing van nabij infrarood reflectie spectroscopie (NIRS) als analyse techniek voor de bepaling van het vetgehalte van slachfkuikens. COVP-uitgave No. 487.

Valdes, E.V., Atkinson, J.L., Hilton, J.W. and Leeson, S., 1989. Near infrared reflectance analysis of fat, protein and gross energy of chicken and rainbouw trout carcasses. Can. J. Anim. Sei., 69: 1087-1090.

220

PLOT FOR BREAST MEAT PLOT FOR ORUrtSTTCX

PLOT FOR THIQM

31 35 39 A7 51 55 53 S3

Figure 1 Prediction of fat content by NIRS.

221

222

CARCASS WEIGHT AND ULTRASONICS TO SELECT BROILERS FOR BREAST MEAT YIELD

M. Kooij-Krijgsman and C.H. Veerkamp

Spelderholt Centre for Poultry Research and Information Services, Agricultural Research Service (DLO), 7361 DA Beekbergen, The Netherlands

Abstract

A good prediction of the breast meat weight is possible from carcass weight (^=0.85). The prediction of breast meat weight is improved by using the multiple regression based on carcass weight and ultrasonic value (r2=0.90).

Introduction

In poultry industry the quantity of breast meat is important because it is the most valuable part of the broiler. Breast meat yield is therefore an interesting aspect in paying the growers. For process tuning prediction of the breast meat weight is desired for selecting uniform carcasses at each production line for cutting. The amount of breast meat should thus be known at an early stage of processing. Presently the decision to cut the carcasses mainly depends on the carcass weight.

Selection criteria for birds to cut up can be for example carcass weight, breast length, breast width or breast thickness (Gühne, 1969). Another method of measuring breast thic­kness is ultrasound. Preliminary investigations at the Spelderholt (Krijgsman 1987; Kooij-Krijgsman and Veerkamp, 1989) with ultrasonic measurements to estimate the breast meat yield of broilers were carried out. These measurements were quite encouraging for predicting the yield of breast meat for flocks of broilers. The prediction of the individual breast meat weight was more accurately then the breast meat yield (correlation coefficients of about 0.70 respectively 0.55, Komender and Grashorn, 1990). The same magnitude of correlations was found in our own experiments. Measurements on different flocks and a large number of birds should result in more reliable equations for prediction of breast meat content. A combination of ultrasonic measurement and carcass weight could improve the correlation with breast meat weight or percentage for individual carcasses. The ultrasonic measurement or the carcass weight was checked for sufficient relationship with the amount of breast meat to select individual broiler carcasses for cutting.

223

Materials and Methods

Random samples of 40 birds each were collected from 48 broiler flocks of different breeds. Sexes were equally represented in the samples. The breast meat weight and breast meat yield was estimated according to the standard method of the WPSA, European Federation working Group V (Fris Fensen, 1984). After cutting the breast meat in this way, the remaining parts of the breast meat are removed from the carcass to estimate the total amount of breast meat accurately. The breast meat yield was calculated as percentage of the individual live weight of the broiler. The carcass was defined as the eviscerated carcass including abdominal fat, without neck and neckskin.

The principle of the ultrasonic measurements is: the transmitted beam of ultrasound waves is partly reflected by a boundary between two différent tissues. The reflected part is received and converted in an electrical signal and shown as a peak on the display of the equipment. The ultrasonic measurements were done with a Krautkrämer USM2 head (d = 13 mm). The measuring locus was at the left side of the highest point of the breastbone (Figure 1). This locus was used, because previous measurements showed the best correlation with breast meat yield there (Krijgsman, 1987).

Single and multiple regressions were calculated between breast meat (as weight and as a percentage) as dependent variables and ultrasonic value and/or carcass weight as the independent variables.

Results and Discussion

The mean carcass and breast meat weights for the flocks are presented in Table 1. The correlations within flocks are presented in Table 2. The correlation within flocks between breast meat yield and carcass weight is hardly ever significant. The correlation between breast meat yield and ultrasonic value within flocks is significant for all flocks except for 7 flocks. The correlation between breast meat weight and ultrasonic value is significant within flocks, except two flocks. The correlation between breast meat weight and carcass weight within flocks is significant for all flocks.

The results of the regression calculations for individual broilers are shown in Figures 2 -5, as well as the linear regression equation and the 95 % reliability interval. Carcass weight predicts breast meat weight better than breast meat yield. Ultrasonic value also indicates breast meat weight better than breast meat yield.

224

The regression equations are :

bmg = 0.215 * cw - 11.35 (^=0.85) bmg = 66.95 * uv - 52.53 (r2=0.49) bm% = 0.0015 * cw + 12.07 (r2=0.06) bm% = 1.482 * uv + 7.483 (r2=0.35)

bmg = breast meat weight (g), bm% = breast meat percentage (%), uv = ultrasonic value, cw = carcass weight (g)

Calculations of the regression equations (Rincker and Veerkamp, 1989) do not confirm the results of preliminary experiments (Kooij-Krijgsman and Veerkamp, 1989) which showed high correlation between mean ultrasonic value and average breast meat yield of flocks. The results of regression calculations on individual broilers presented in this paper are in agreement with the results of earlier research (Krijgsman, 1987; Komender and Grashorn, 1990). Increasing the number of flocks and total number of measurements (comparing this experiment with earlier results) has no effect on the reliability of the prediction of breast meat yield or weight. The best prediction of breast meat weight is from carcass weight. The prediction is ± 35 g using a reliability interval of 95 %.

The following multiple regression equations are calculated :

bmg = 0.179 * cw + 26.62 * uv - 84.2 (r2=0.90) bm% = -0.00068 * cw + 1.634 uv + 7.6 (r2=0.35)

Comparing these multiple regression equations with the linear regression equations it can be concluded that : - Breast meat weight is best predicted by carcass weight and ultrasound combined. Using

the multiple regression equation the calculated amounts of breast meat are compared with the actual values. This is shown in Figure 6. The calculated value is within ± 29 g comparing the actual value with a reliability of 95 %. This means an improvement of 17 % for the prediction of breast meat weight comparing the linear regression equation based on carcass weight.

- Breast meat yield prediction is not increased by using multiple regression compared with the linear regression equation based on ultrasonic values. The prediction of the breast meat yield of individual carcasses is + 1.9 % with 95% reliability.

225

Conclusion

Breast meat weight of individual broiler carcasses can be predicted at ± 35 g with a reliability of 95 % from carcass weight. The prediction is ± 29 g if carcass weight and ultrasound are used.

References

Gühne, W.A.E., 1969. Die Beurteilung der Brustmuskulatur von Broilern mit Hilfe von Konformationsnoten und mechanische Messverfahren. Dissertation der Hohen Agrarwissenschaftlichen Fakultät der Universität Hohenheim.

Fris Jensen, J., 1984. Method of dissection of broiler carcasses and description of parts. WPS A European Federation working group V.

Komender, P., Grashorn, M., 1990. Ultrasonic measurement of breast meat. Poultry International 54, 3, 36-40.

Kooij-Krijgsman, M., Veerkamp, C.H., 1989. Ultrasonic measurement of breast meat yield. Poultry International 53, 12, 44-48.

Krijgsman, M., 1987. Ultrasone bepaling van de bevleesdheid. COVP Uitgave 473, Spelderholt Centre for Poultry Research and Information Services, 7361 DA Beekbergen, The Netherlands.

Rincker, A.H.H., Veerkamp, C.H., 1989. Het voorspellen van het percentage borstvlees van slachtkuikens met behulp van een ultrasoon bepaling. COVP-uitgave no. 515, Spelderholt Centre for Poultry Research and Information Services, 7361 DA Beekbergen, The Netherlands.

226

Table 1 Means of flocks.

Flock

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

Live weight

1904 1651 1690 1536 1408 1634 1802 1717 1770 1862 1638 1685 1645 1692 1921 1783 1771 1905 1976 1917 1979 1635 1862 2748 1790 1724 1844 1768 1701 1709 1522 1250 1538 1460 1567 1570 1785

Carcass weight

1289 1106 1143 1032 934 1129 1222 1181 1235 1283 1108 1164 1126 1140 1323 1206 1203 1312 1363 1308 1320 1086 1251 1196 1204 1169 1248 1198 1140 1162 1013 819

1039 945 1027 1027 1190

Breast meat weight

268.4 224.1 238.0 208.1 190.1 224.1 242.8 241.8 240.5 265.1 225.0 236.9 233.3 218.9 270.5 235.2 237.6 277.1 264.6 266.3 276.7 218.0 259.6 251.4 246.5 238.5 258.6 245.4 229.7 254.5 204.2 158.6 226.7 187.2 208.3 221.1 240.1

Breast meat yield

14.11 13.62 14.08 13.55 13.50 13.70 13.48 14.03 13.58 14.23 13.74 14.07 14.18 12.92 14.06 13.20 13.41 14.55 13.37 13.89 13.91 13.32 13.92 14.35 13.75 13.81 14.05 13.86 13.53 14.88 13.41 12.66 14.72 13.27 12.78 14.08 13.42

Ultrasonic value

4.672 4.085 4.324 4.057 3.998 4.300 4.290 4.496 4.141 4.403 4.353 4.532 4.174 4.056 4.492 4.216 4.187 4.465 4.257 4.664 4.715 4.157 4.568 4.111 4.395 4.311 4.412 3.867 4.113 4.705 4.144 3.682 4.578 3.847 4.132 4.305 4.008

227

Table 1, continued

Flock

38 39 40 41 42 43 44 45 46 47 48

Live weight

1399 1558 1517 1499 1588 1490 1496 1358 1822 1938 1969

Carcass weight

933 1041 1033 1008 1069 1001 1017 900 1239 1350 1368

Breast meat weight

183.6 216.6 204.1 201.1 211.8 190.4 197.6 200.6 278.5 290.3 307.0

Breast meat yield

13.12 13.84 13.48 13.41 13.35 12.80 13.21 14.72 15.23 14.97 15.59

Ultrasonic value

3.808 4.185 3.969 3.941 3.985 3.721 3.885 4.535 4.915 4.870 4.864

228

Table 2 Correlations within flocks.

Breast meat yield Flock Ultrasonic Carcass

value weight

Breast meat weight Ultrasonic Carcass value weight

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

.478**

.584***

.588***

.448**

.563***

.430**

.454**

.694***

.392*

.237

.470**

.408**

.442**

.533***

.275

.335*

.545***

.109 743*** 446***

700*** .488** .500** .391* .766*** .453 .583*** .505*** .566*** ß2\***

.070

.501** 577***

.142 -.094 .493**

.098 -.184 .085 .031 .079 .213 -.085 .323 -.090 .0112 .083 -.142 .062 .165 -.281 -.128 .146 .025 -.073 .134 499**

.062

.269

.265

.313

.302 -.056 .203 .010 .121 .174 .313 .204 .057 .165 .146

.655***

.683*** 7]Q***

.535***

.612***

.486**

.538***

.801***

.276

.462**

.663***

.530***

.568***

.620***

.403*

.566***

.676***

.583***

.570***

.684*** 782***

.605***

.753***

.540*** ^74***

.518**

.492**

.470**

.517** 729***

.088

.561***

.669***

.800***

.629***

.556***

mo***

744*** g73***

.866*** 782*** gg7*** gß2***

.935*** gg7***

.828*** g7j***

.853*** g97***

.854*** 772***

.880*** 930*** 915*** g7j*** g7Q***

920*** .840*** 903*** 915*** g79***

908*** .814*** 910*** gg7***

916*** .806*** .895*** 939*** 929***

.858*** 915***

229

Table 2, continued

Breast meat yield Flock Ultrasonic Carcass

value weight

Breast meat weight Ultrasonic Carcass value weight

37 38 39 40 41 42 43 44 45 46 47 48

* p ** p *** p

< < <

0.10 0.05 0.01

.575*** 473** 740***

.417**

.538***

.581***

.352* 559***

.662***

.722*** 593***

.368*

.286

.016

.389* -.104 .230 -.021 -.068 .058 .437** 542***

.361* -.027

645*** 550*** 690*** 487** 709*** 410** ,492** 509***

805*** 760*** 784*** 79***

g99*** .906*** 910***

.860*** 9J4***

.812***

.850***

.869*** 929*** 954*** 904*** 904***

230

Figure 1 Measuring locus for ultrasonic measurements on the breast.

460

350

260

150

50

breast meat (q)

_i_

700 900 1100 1300 1500 1700 1900

carcass (g)

Figure 2 Results of regression calculations between carcass weight and breast meat weight for individuals.

231

2 0

18

16

14

12

10 h

breast meat (%)

, ------'-*•>'-'?'-i?~t'f&'ï''/"'-"-'ri•"'

J I I I I I I I l_ 8 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1600 1 8 0 0 2 0 0 0

carcass (g)

Figure 3 Results of regression calculations between carcass weight and breast meat yield for individuals.

4 0 0

3 0 0

2 0 0

breast meat (g)

100

« . ' " '""

• * * < . • * " * ' .

* " * * ' * * ^t******"^

! . _ - - ! ' " : : . i i ' . '• ^ ^ " ^

'. . .ù-1-i's" • , - ' ' " ' • ! : !

.-

i i i

- ' ,-

•"% ' ; : • i • ; i - ' .

. - - ' i . i . i , i , i ,

3.0 3.5 4.0 4.5 5.0 5.5 6.0

ultrasonic value

Figure 4 Results of regression calculations between ultrasonic value and breast meat weight for individuals.

232

20

18

breast meat (%)

10 3.00 3.50 4.00 4.50 5.00 5.50 6.00

ultrasonic value

Figure 5 Results of regression calculations between ultrasonic value and breast meat yield for individuals.

4 0 0

3 0 0

actual breast meat (g)

2 0 0

4 0 0

calculated breast meat (g)

Figure 6 Comparing calculated brest meat weight and actual breast meat weight for individuals.

233

234

CRITERIA OF SELECTION FOR HIGHER BROILER CHICKEN BREAST YIELD

A. Migineishvili

Poultry Research Institute, Kostinbrod 2230, Bulgaria

Abstract

Results from an investigation aiming to assess the criteria of selection for higher breast meat yield in broiler chickens are reported. Six hundred chickens of line 66, White Cornish sire strain reared up to the age of 7 weeks were used. Three methods for in vivo prediction of breast meat yield were tested: measurement of breast muscle depth by needle perforation (BMD), of breast length (BL) and of length of breast bone keel (LBBK) measured with a band. Tlie correlation of BMD with breast weight was higher (r=0.61-0.66) than the correlation of BL and LBBK (r= 0.02-0.34). It was concluded that BMD could be successfully used as an in vivo criterion for breast meat yield. Regression equations and BMD values could be applied as predicting indexes for breast meat yield of broiler chickens. After these preliminary studies the same broiler size strain was diverged into two lines according to the BMD index (HD and LD) and observed in Fj at age 7 weeks. Tire diverged selection for BMD with mean F, values 14.61 mm (body weight 1939 g) for males and 14.50 mm (live body weight 1572 g) for females led to the following results in

1. Chickens from the HD line had 20-30 higher body weights than those from the LD line and better feed conversion (2.12 versus 2.16).

2. Breast meat yield of the HD line was 0.2-0.5% higher than that of the LD line but the percentage of abdominal fat was lower (0.1-0.3%).

BMD is considered a useful criterion in broiler stock selection due to its correlation with higher breast meat yield.

Introduction

Selection for higher broiler productivity is based mainly on growth rate. This is one of the characters determining chicken body weight and meat yield. Most recent trends in chicken meat production are determined by the marketing of: whole chickens, cut-up form chicken meat and boneless meat. Poultry breeders have to take into consideration the requirement of these markets. Therefore a number of breeding programs focus their attention not only on yield and body weight, but also on body shape and quantity of meat from the separate parts.

235

Production of chickens with lower yield and lower breast muscle percentage is considered unprofitable both for breeders and for broiler chicken meat producers. Body weight, output and breast meat yield are mutually correlated indices. In poultry processing the output increases along with the increase of body weight. The same correlation exists between body weight and breast muscle. Body weight, slaughter weight and breast weight increase linearly from the 28th to the 70th day (Perreault and Leeson, 1987). Breast muscle weight in cutting-up depends on body weight, hybrid and sex. At equal body weight female chickens have higher relative share of breast muscle. It must be noted that using slaughter indices for breeding is a very labour consuming process because cutting up of the separate parts of the carcass is manually performed. Therefore, at present the question of determining (predicting) meat yield characteristics in vivo is of great importance. Among these characteristics breast meat weight ranks first. Up to the present practical poultry breeding predicts breast muscle quantity after the following methods: evaluation of the musculature using a scale determining the breast angle; measurement width and length of breast muscle and of the breast bone. These measurements have low, unsatisfactory correlations with breast meat weight. Breast meat yield can be predicted also by the depth of the breast muscle. Bochno (1979) reports that in vivo evaluation of breast muscle depth is an objective index for turkey breast musculature. The author found a high positive correlation between the depth and weight of breast muscle (r=0.6). Pingel and Heimpold (1983) selecting ducks by body weight and breast depth (determined by perforation) in the course of 7 years, found that the breast muscle's depth increase 0.04 cm per generation. Along with that body weight increased by 72 g per generation. The result of this selection led to a higher relative share of breast meat in the carcass. High correlations were found by ultrasonic measurements of breast meat and breast meat yield (Kooij-Krijgsman and Veerkamp, 1989; Komender and Grashorn, 1990). The aim of the present study was to assess the possibility of using breast muscle measurements as criteria for increased breast meat in broiler chicken breeding.

Material and Method

The study was carried out at the Poultry Research Institute, Kostinbrod. Six hundred chickens chosen at random from the White Cornish sire strain were reared up to age 7 weeks. The following indices were observed. 1. Live weight of the chickens at age 7 weeks. 2. Breast muscle depth (BMD) in mm. This index was determined by a graded needle

especially constructed for the purpose with an allowance of 1 mm. The spot where the depth value was measured was on the left hand side and the perforation was made directly to the top of the breast bone.

3. Length of breast bone keel (LBBK) in mm, measured with a band from the anterior to the posterior of the breast bone's keel.

236

4. Breast length, mm, measured with a band from the front of the breast line to the back end of the breast bone's keel (BL).

5. Breast weight, g, measured in 120 randomly chosen chickens intended for slaughter analysis with indices near to the average values for the whole group of chickens (Table 1). Breast meat was weighed without the skin and the breast bone was removed.

After breast measurement evaluation of the chickens the population was diverged into two lines according to BMD in Fl generation - HD (high depth of breast muscle) and LD (low depth of breast muscle). In F, the selection pressure for BMD was 22% at -0.6 mm selection difference for LD line and +0.8 mm selection difference for HD line. The poultry progenies (two broods) of the diverged lines were tested for body weight, feed conversion and BMD (Table 3). In F, generation selection pressure was the same as selection difference for LD line 0.7 mm and for HD line 0.6 mm. Two broods were produced by these lines (F3), which were tested in small boxes sized 1.0 x 0.8 m and fed ad libitum with feeds containing 12.1 MJ/kg and 221 g/kg protein up to age 7 weeks. The same indices percentage of breast and abdominal fat involvement in respect to body weight and feed conversion were measured (Table 4).

Results and Discussion

Data about results concerning chicken body weight and the other measurements are presented in Table 1.

Table 1 Mean values and standard deviations of body weight and breast measurement in 7 weeks old chickens (F,).

Characters Sex

Body g

BME mm

LBB1 mm

BL mm

Breaj

S

weight

)

!C

>t meat

male female

male female

male female

male female

male female

280 288

280 288

280 288

280 288

60 60

1939 ± 183 1572 ± 166

14.6 ± 1.0 14.5 ± 0.9

109.3 ± 6.3 144.6 ± 6.7

149.2 ± 6.2 142.4 ± 6.0

233 ± 29 190 ± 21

237

Differences between mean breast measurement values of the male and female chickens for BMD were small and statistically insignificant but for BL and LBBK they were statistically significant (p<0.0001). Correlations between these measurements for body weight and breast meat weight were positive, a fact indicating the possibility for indirect selection for the indices BMD, BL and LBBK which could lead to increased yield of breast meat.

Table 2 Correlations between body weight and breast measurements1.

Female Male

BDM 0.66"* 0.60"* LBBK 0.28* 0.06 BL 0.34* 0.02

1 n=60, "* p<0.001, * p<0.05.

Poultry breeders today are certain that mass selection for body weight is not sufficient and know also that a quick improvement of a characteristic could be attained when selection for that characteristic is performed. However, direct selection for higher breast meat yield is impossible, because this characteristic is assessed by slaughter analysis. Therefore any other characteristic predicting it by measurements on live chickens would be promising in indirect selection for breast meat yield. The presented hypothesis aiming to assess the possibilities of using breast muscle measurements as a criterion in selection for higher breast meat yield has a positive response to BMD: a. BMD had higher phenotypical correlation values with breast meat (r=0.61 for males

and 0.66 for female chicks). The correlations of LBBK and BL were of very low value.

b. BMD was quickly assessed (by perforation), a fact of great practical importance in mass selection.

c. BMD could be used also in predicting breast meat yield in broiler chicken production. The following regression equations were estimated in our experiment: c v y = 141.6 + 8.9 x ?? y = 115.1 + 8.7 x x = BMD values y = breast meat

238

After diverging the two experimental lines according to BMD their progeny differed in body weight (statistically insignificant differences) and for BMD in the first brood with 0.5 mm in male chickens and 1.6 mm in female chickens, as well as 0.4 mm in the second brood for both sexes in favour of the HD line.

Table 3 Mean values and standard deviations of body weight, BMD and feed conversion1 (F2).

Characters

Body weight

g

BMD mm

Sex

male female

male female

Feed conversion per kg

1st brood HD

1914 + 190 1555 ± 119

14.6 ± 0.8 13.6 + 0.9

2.21

LD

1880 ± 215 1530 + 119

141. + 1.1 12.0 ± 0.9

2.20

2nd brood HD

2211 ± 209 1767 ± 127

14.7 ± 0.9 13.8 ± 0.8

2.09

LD

2158 ± 192 1722 ± 146

14.3 ± 0.9 13.4 ± 0.8

2.18

1 = 50 chickens per group.

In the second brood - HD line and feed conversion was 90 g lower. The following generation was also tested by progeny in two broods.

239

Table 4 Mean values and standard deviations of the characters in the diverged lines1

(F3).

Characters

Body weight

g

BMD (mm)

LBBK (mm)

BL (mm)

Sex

o"

¥

o*

?

0*

¥

0*

?

1st brood HD

1947 ± 114 1601 ± 94

16.3 ± 1.7 14.7 ± 1.3

104.0 ± 6.2 99.0 ± 6.1

146.5 ± 6.5 141.4 + 6.4

LD

1931 + 113 1573 + 99

14.8 + 2.3 13.9 + 1.19

104.0 + 5.1 98.9 ± 3.8

148.5 + 6.0 140.0 ± 5.5

2nd brood HD

1999 ± 144 1627 + 127

16.4 ± 1.3 16.0 + 1.8

104.3 + 5.4 97.7 ± 6.1

143.4 ± 6.5 134.4 + 6.7

LD

1919 ± 61 1588 ± 41

16.1 + 1.2 15.1 ± 1.2

102.8 + 4.2 95.8 ± 3.9

143.5 ± 4.2 136.4 ± 6.5

% of breast meat in respect to body weight

¥

% of abdominal fat respect to body wei;

0"

¥

Feed conversion kg

12.3 ± 1.0 12.8 + 1.0

in ght

1.7 + 0.6 2.1 + 0.8

2.12

12.1 + 0.9 12.5 + 1.0

1.8 ± 0.5 2.3 ± 0.6

2.16

12.0 + 1.0 12.3 ± 1.0

2.0 ± 0.8 2.5 ± 0.7

2.01

11.5 ± 0.9 11.8 + 1.0

2.2 + 0.6 2.8 + 0.9

2.02

1 _ 60 chickens per group.

A trend was observed toward higher meat qualities of HD line as compared to the LD line. Body weights of HD line chickens were higher than those of LD line (statistically significant differences only for male chickens from 2nd brood (psO.001). Almost no differences were found in data about the two lines for the indices BL and LBBK, but the values for BMD of the HD line were statistically significant (excepting male chickens of the 2nd brood). This could be explained by the divergent selection for this index. It leads to higher indices of breast meat yield. The percentage involvement of breast meat in body weight was higher in the HD line (by 0.2-0.5), while that of abdominal fat was lower as compared to the LD line.

240

Feed conversion produced higher results in chickens of the HD line. Results of the studies with broiler chickens concerning breast measurements in vivo substantiate the conclusion that BMD could be used as a criterion in selection for higher breast meat yield. Selection for BMD could produce a positive effect in breeding programs for broiler lines with higher breast meat yield.

References

Bochno, R. and Michalik, D., 1979. Roczniki Naukowe Zootechniki 6 (1), 45-54. Komender, P. and Grashorn, M., 1990. Ultrasonic measurement of breast meat. Poultry

Int. 54, 3, 37-40. Kooij-Krijgsman, M. and Veerkamp, C.H., 1989. Ultrasonic measurement of breast meat

yield. Poultry Int. 53, 12, 44-48. Perreault, N.A. and Leesen, S., 1987. Demand for breast yield to increase. Poultry 3 (2). Pingel, H. and Heimpold, M., 1983. Effektivität der Selection auf Lebendmasse und

Brustfleischanteil bei Enten. Arch. Tierzucht 26 (5), 435-444.

241

242

NEAR-INFRARED SPECTROSCOPY (NIRS) AND (POULTRY) MEAT ANALYSIS

A.T.G. Steverink

Spelderholt Centre for Poultry Research and Information Services, Agricultural Research Service (DLO), 7361 DA Beekbergen, The Netherlands

Abstract

A near-infrared spectroscopy (NIRS) calibration curve for a fast screening of the linoleic acid content of poultry meat was developed. Using the partial least squares (PLS) regression technique a correlation coefficient (R) (between NIRS and gas chromatography) of 0.976 and a standard error of calibration (SEC) of 2.17% were obtained. Validation gave R- and SEP (standard error of prediction) of 0.969 and 2.00 respectively.

For whole broiler carcasses (including feathers and bones) NIRS calibration curves for the analysis of moisture, fat and protein were developed. PLS-regression yielded R values of 0.988, 0.989 and 0.924 and SEC values of 0.35, 0.38 and 0.031, respectively. The respectively validation values for R and SEP were 0.988 and 0.40, 0.984 and 0.54 and 0.595 and 0.047.

Introduction

After the introduction of eggs with a significant higher linoleic acid content, a broiler production chain with a similar idea was set up (Terbijhe, 1991). To control whether or not is met the requirements, a fast screening method for the determination of the linoleic acid content of whole dressed broiler carcasses, legs and wings was developed. As near-infrared spectroscopy has proved its abilities for similar analysis of eggs (Steverink et al., 1990), it was likely that this technique should work for the determination of the linoleic acid content of (poultry) meat (parts) as well. The development of the calibration curve is described in this paper.

243

Although the determination of the moisture, fat and protein content of meat with NIRS belongs to the very first applications of this elegant technique (Ben-Gera and Norris, 1968), the prediction of those parameters for whole poultry carcasses, feathers and bones included, has not been published yet. Results of NIRS analysis of whole rabbit carcasses, including skin and bones, (Steverink and Steunenberg, 1990), indicate that NIRS analysis of this type of (inhomogeneous) samples is possible. Preliminary results of the development of calibration curves for whole poultry carcasses are given as well.

Materials and Methods

Linoleic acid

For the development of the calibration curve for the determination of linoleic acid in poultry meat, broilers were raised on diets with a linoleic acid content (on fat basis) between approximately 25 and 60%. The legs of these broilers were used for analysis. Prior to analysis, the legs of the slaughtered animals were homogenized with a cutter (Alexanderwerk SNZ 20) and a mincer (Hobart N-50). The homogenized samples were scanned in duplicate with a NIRSystems 6500 (Perstorp Analytical Company), using a "high-fat high-moisture" sample eel. Reference analysis were performed in fat extracted from the scanned samples, according to a specially modified extraction procedure (Steverink et al., 1991). Linoleic acid was analyzed gas chromatographically, as described by Badings and De Jong (1983), using a Carlo Erba Mega GC equipped with a cold on-column injector, a 50 m x 0.32 mm ID fused silica column (CP-Wax 52 CB, Chrompack) and a flame ionization detector. The averaged spectral data and the average GC data were used for PLS regression analysis.

Moisture, fat and protein

For the development of calibration curves for the moisture, fat and protein content of whole carcasses 96 samples, consisting of 3 animals each, were used. The killed animals were frozen, ground with a cutter (Alexanderwerk SSK 45) and further homogenized with a mincer (Kilia H-82). Next each samples was scanned in duplicate as described in the previous section. Reference analysis were performed according to the usual procedures (NEN 3440, 3442 and 3443).

244

Results

Linoleic acid

From the overall sample set a calibration set was randomly selected. PLS-regression using 1 -15 factors gave correlation coefficients (R) from 0.320 - 0.986 (Table 1). According to an optimization program the regression equation of 8 factors should be used. The corresponding standard error of calibration (SEC) is 2.17. The advised equation applied to the validation set (= overall set - calibration set) resulted in an R-value of 0.969, only slightly lower than that of the calibration set (0.976) and a standard error of prediction (SEP) of 2.00, even better than the SEC-value. These results show, that the calibration is almost perfect.

Moisture, fat and protein

For the moisture, fat and protein content, the R- and SEC-values from the PLS-regression developed as shown in Table 2. For all three parameters the optimization program advised the use of the regression equation obtained with 14 factors. Using these equations for the validation set the R- and SEP-values are 0.983 and 0.48, 0.984 and 0.54 and 0.573 and 0.048, respectively. Before the installation of the optimization program our selection involved only 5 factors for moisture and fat and 9 for protein. The corresponding equations gave the R- and SEP-values presented in Table 3. Both values are shown in this table. Using 14 factors yields for all 3 parameters a higher R and a lower SEC. However, the predictive value with 5 factors is better. Both R- and SEP-values differ only slightly for the calibration and the validation set, using 5 factors. Obviously, more work needs to be done for protein, since R-values drop tremendously for the validation set.

Conclusions

To distinguish "normal" broilers from those with a higher linoleic acid content (< 30% versus > 40%), the developed calibration curve is almost perfect. For the determination of the moisture and fat content of whole broiler carcasses, including feathers and bones, very acceptable calibrations curves have been obtained. For the estimation of the protein content, calibration needs improvement.

245

References

Badings, H.T. and C. de Jong (1983). Glass capillary gas chromatography of fatty acid methyl esters. A study of conditions for the quantitative analysis of short- and long-chain fatty acids in lipids. J.Chromatogr., 279, 493-506.

Ben-Gera, I. and K.H. Norris, 1968. Direct spectrophotometric determination of fat and moisture in meat products. J.Food Sei., 33 (1), 64-67.

NEN 3440, 1968. Determination of the moisture content of meat and meat products. Nederlands Normalisatie Instituut, Delft, The Netherlands.

NEN 3442, 1968. Determination of the nitrogen content of meat and meat products. Nederlands Normalisatie Instituut, Delft, The Netherlands.

NEN 3443, 1968. Determination of the fat content of meat and meat products. Nederlands Normalisatie Instituut, Delft, The Netherlands.

Steverink, A.T.G. and H. Steunenberg, 1990. Determination of the composition of whole rabbit carcasses by means of near-infrared reflectance spectroscopy (NIRS). Proceedings Third International Conference on Near-Infrared Spectroscopy, Brussels. In press.

Steverink, A.T.G., H. Steunenberg and J.K. Waltmann, 1990. Determination of the linoleic acid (CI8:2) content in eggs by means of near-infrared reflectance spectroscopy (NIRS). Proceedings Third International Conference on Near-Infrared Spectroscopy, Brussels. In press.

Steverink, A.T.G., A.J.N. Bisalsky & H. Bleumink, 1991. The extraction of fat from products with a high polyunsaturated fatty acids content. Spelderholt Report Nr. 550.

Terbijhe, R.J., 1991. Quality controlled meat: NATUPUR - an integral production chain surveillance concept. Symposium on Quality of Poultry Products, Vol. Ill Safety and Marketing Aspects, May 12-17, Doorwerth, The Netherlands.

246

Table 1 Correlation coefficients (R) and standard errors of calibration (SEC) during PLS-regression analysis for linoleic acid (89 samples; linoleic acid range 21.3 -51.8%).

Factor

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15

R

0.320 0.636 0.854 0.915 0.953 0.970 0.975 0.976 0.979 0.981 0.981 0.984 0.985 0.985 0.986

SEC

9.13 7.48 5.07 3.96 2.99 2.40 2.22 2.17 2.09 1.98 1.97 1.86 1.80 1.78 1.75

Table 2 R- and SEC-values for moisture, fat and protein content. Calibration set: 67 samples. Ranges: moisture 59.4 - 69.2%, fat 8.7 - 19.6%, nitrogen (protein) 2,74 - 3.08%.

Factors

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15

Moisture R

0.863 0.976 0.980 0.985 0.988 0.989 0.992 0.995 0.996 0.996 0.997 0.998 0.998 0.999 0.999

SEC

1.09 0.48 0.44 0.38 0.35 0.34 0.28 0.23 0.22 0.20 0.18 0.17 0.15 0.13 0.12

Fat R

0.868 0.977 0.983 0.985 0.989 0.990 0.992 0.994 0.995 0.996 0.996 0.997 0.998 0.998 0.999

SEC

1.25 0.54 0.47 0.44 0.38 0.37 0.34 0.30 0.28 0.26 0.24 0.21 0.19 0.16 0.14

Protein R

0.638 0.701 0.721 0.769 0.795 0.833 0.879 0.900 0.924 0.936 0.953 0.958 0.970 0.978 0.983

SEC

0.058 0.054 0.053 0.049 0.047 0.043 0.037 0.035 0.031 0.028 0.025 0.024 0.020 0.017 0.016

247

Table 3 Comparison of R- and SEC/SEP-values for calibration and validation set, using 5 (9) and 14 factors.

Moisture Fat Protein

5 (9) Calibration

R

0.988 0.989 0.924

SEC

0.34 0.37 0.028

factors Validation R

0.998 0.984 0.595

SEP

0.40 0.54 0.047

14 factors Calibration

R

0.999 0.998 0.978

SEC

0.12 0.14 0.016

Validation R

0.983 0.984 0.573

SEP

0.48 0.54 0.048

248

SESSION M4

FACTORS RELATED TO PRODUCT QUALITY

249

250

LITTER CONDITION AND CONTACT DERMATITIS IN BROILER CHICKENS

N.J. Lynn1, S.A. Tucker2 and T.S. Bray3

1 Agricultural Development Advisory Service, Ministry of Agriculture Fisheries and Food, Government Buildings, Lawnswood, Leeds LS16 5PY United Kingdom

2 Gleadthorpe Experimental Husbandry Farm, Meden Vale, Mansfield, NG20 9PF United Kingdom

3 Agricultural Development Advisory Service, Ministry of Agriculture Fisheries and Food, 122a Thorpe Road, Norwich, NR1 1RN United Kingdom

Abstract

The lesions of contact dermatitis are unsightly brown-black erosions that occur on the breast, thigh, hock and foot skin of broiler chickens and turkeys. These lesions can be of economic importance to the broiler industry if they reduce the acceptability of the carcass and will be detrimental to bird welfare, especially if they result in impaired mobility. Experimental work has identified 3 conditions of the litter surface which are associated with an increased incidence of contact dermatitis. These conditions are wet litter, greasy litter, and high litter nitrogen. Deterioration of the litter surface is a multifactorial problem affected by the environment control, nutrition, house design, litter material and depth, flock health, and stocking density.

Introduction

"Contact dermatitis" is the collective term for a number of conditions that share common aeteological factors. These conditions are similar in histopathology and include hock burns, breast blisters or faecal burnspots, pododermatitis and scabby-hip syndrome (Green et al., 1985, Hemminga and Vertommen, 1985, Randall et al., 1984, Harris et al., 1978, Page, 1974). The lesions have been described as "unsightly brown-black erosions which occur on the breast, hock and foot skin" (Green et al., 1985). Histopathological examination of these lesions reveals acute inflammation and necrosis of the epidermis, which in severe cases penetrates as far as the upper dermis. Once damaged in this way the skin is open to microbiological invasion. Although a variety of bacteria and fungi have been isolated from hock and breast lesions, there is no apparent difference between the flora of damaged and undamaged skins (Green et al., 1985). In the fattening turkeys secondary invasion of hock

251

lesions resulted in inflammation of the tendon sheaths and subsequent damage to the joints (Martland, 1984). Plantar pododermatitis in turkeys is quite clearly painful and can lead to an increased incidence of lameness (Martland, 1984). Contact dermatitis has a similar effect on broiler chickens (Martland, 1985). The incidence of contact dermatitis in the UK broiler flock is difficult to estimate. A longitudinal survey indicated that approximately 20% of broilers are afflicted with hock lesions and 0.3% with breast lesions. This has serious implications for both the profitability of a broiler enterprise and bird welfare (Mcllroy et al., 1986). The financial cost of contact dermatitis can be estimated in terms of a loss of carcass quality. Grade B carcasses, downgraded due to hock burn, are worth 9p/kg less than premium carcasses (Pattison, 1987). In addition to being blemish free, premium grade carcasses must be of a high microbiological quality. Very scabby carcasses may have a high microbiological count and in some cases could present food hygiene problems (Fehlhaber et al., 1987). Contact dermatitis is sometimes associated with a depression in bird weight (Bray and Lynn, 1986, Martland, 1985, Martland, 1984). Consequently, the producer has to bear the added financial penalty of lower growth rates and poorer feed conversion efficiency. The cost of contact dermatitis in terms of bird welfare is increased suffering due to the pain resulting from damaged areas of skin (Martland, 1985, Martland, 1984). There is also lameness, especially in turkeys (Martland, 1984), which leads to impaired mobility and further skin damage.

Lesion aeteology

The incidence of contact dermatitis has been closely linked with poor litter condition (Pattison, 1987, Bray and Lynn, 1986), which can be defined using a number of factors. Experimental work at Gleadthorpe EHF, Nottinghamshire, UK, and elsewhere (Bray and Lynn, 1986, Hemminga and Vertommen, 1985, Martland, 1985) has identified 3 conditions of the litter surface which are strongly correlated with the incidence of contact dermatitis and especially hock burn in both male and female broilers. These conditions are wet litter, greasy litter, and high litter nitrogen (Diagram 1).

Wet litter

Litter moisture is the key to the burnt hock problem (Bray and Lynn, 1986, Martland, 1985, Martland, 1984). Broilers and turkeys kept on artificially wet litter developed severe foot and hock lesions (Martland, 1985, Martland, 1984), which recovered once the birds were moved on to dry shavings, Experimental data (Bray, 1985, Lynn and Spechter, 1987), and field experience (ADAS personal communication) shows that when the litter

252

moisture exceeds 46% the litter surface will become wet and unfriable. An unfriable litter surface will produce pressure induced lesions at the hock joint where bony prominences lie just below the skin. Severe cases of hock burn are rarely seen in the absence of high litter moisture.

Greasy litter

A greasy cap on the litter surface may form when the litter ether extract exceeds 4.5% (Bray, 1985). High oil levels do not appear to cause damage to the birds. However, litter that has a high ether extract will cap at a lower moisture level. It is the reduction in friability that can lead to an increase in hock and foot damage (Bray and Lynn, 1986).

Litter nitrogen

The most severe cases of hock burn and plantar pododermatitis are associated with levels of nitrogen in excess of 5.5% in the litter surface (ADAS unpublished data). Deterioration of litter friability due to high litter moisture or greasy litter will cause faecal material to accumulate on the litter surface. It is possible that contact with irritant substances in this material can precipitate contact dermatitis. There is some evidence to implicate faecal enzymes in this role (Berg et al., 1986, Buckingham and Berg, 1986).

Factors affecting litter condition

Deterioration of the litter surface is a multifactorial problem affected by environmental control, nutrition, house design, litter material and depth, flock health and stocking density.

Environmental control

Poor litter condition is more likely to occur when the relative humidity within the poultry house exceeds 72% (Payne, 1967). Environmental control can be used to regulate the house water balance in order to control litter moisture. Air is the vehicle for removing water, and litter moisture can be reduced by increasing the heat input and the ventilation rate.

253

The ventilation system should be capable of delivering a minimum ventilation rate of 1.6.10"4 m3 of air per second per kilogram of metabolic body weight. It is necessary to adjust the ventilation system regularly, since the minimum amount of air required by the birds increases in line with their metabolic body weight. Thermostatic control of the ventilation system should operate between the minimum ventilation rate and the maximum rate of 1.4.10"3 m3 of air per second per kilogram of metabolic body weight. The maximum ventilation rate is determined by the birds' peak requirement for air, which is usually just prior to their removal for slaughter. Air inlets should be correctly designed, ensuring that the air distribution within the building remains stable over a wide range of outside weather conditions. Draughts and cold spots within the building can be focal points around which the litter begins to deteriorate. All the ventilation equipment should be maintained to a high standard. Small defects resulting from poor construction, or wear and tear can seriously restrict the performance of the whole system. For example, a fan correctly fitted in the manufacturers bell mouth will supply 10-15% more air than one fitted in a home made wooden mounting ring. The post-brooding temperature should be maintained at the economic optimum, usually between 21 °C and 23°C in UK conditions. In winter it may be necessary to supply extra heat in order to maintain these temperatures without encountering litter quality problems.

Nutrition

Nutritional faults are directly linked to the formation of wet litter, greasy litter and high litter nitrogen. Any dietary factor that increases the birds' water intake will lead to an increase in litter moisture. Such factors include increased sodium, potassium, amino acid and salt levels, the use of ingredients like barley, manioc and soya at above recommended levels, and the use of poor quality protein sources. Table 1 illustrates the effect of different protein sources, amino acid, and sodium levels on the moisture content of the litter surface (ADAS unpublished data). Litter moisture is clearly affected by all 3 factors, and the resulting deterioration in the litter surface led to a reduction in product quality due to increasing hock damage (figure 1). Bird quality was assessed using a 5 point subjective scoring system (0-4), possible downgrades were those birds that fell into scores 3 and 4. The wrong grades or excess quantities of fat in the feed may lead to capped and greasy litter when poorly digested by the birds (Bray, 1985). The effect of increasing the oil level in the litter is to cause it to become unfriable at a lower moisture level. In this way the risk of encountering poor litter conditions and the resulting reduction in product quality is increased.

254

High levels of nitrogen in the litter surface are directly related with dietary protein quantity and quality (Table 2). The precise mechanism by which this nitrogen causes damage to the birds' skin is not known. High levels of nitrogen in the litter may indeed be an artifact related to the reduction in friability that occurs when the litter becomes wet. An unfriable litter surface will be subject to a rapid build-up of faecal material, whereas if the litter is friable this faecal material will be incorporated. However, nitrogenous compounds are known to precipitate irritant reactions in the skin of other species (Mahzoon et al., 1977). In addition, the close association between dietary protein quality and quantity and hock burn (figure 1), ensure that the role of litter nitrogen should not be ruled out. Care should be taken over the inclusion levels of poorly digested ingredients such as poultry offal meal and meat and bone meal.

House design and equipment

The specific environmental conditions can only be met if the building is properly designed. The optimum environmental temperature will not be achieved in cold weather unless the insulation value of the structure is 0.5 W/m2 °C or better. Water spillage from poorly designed or managed drinkers has been shown to result in reduced litter surface friability and wet litter (Lynn and Spechter, 1987). Experimental work has shown that small cup-type drinkers reduce water wastage and improve litter friability. All types of drinkers must be properly installed and regularly adjusted to give good results.

Litter material and depth

The most effective litter material for broiler chickens is wood shavings. Experimental work and field trials have shown that there are alternatives, but these usually require a greater management input (Lynn and Spechter, 1986). This work also suggests that litter conditions are improved if the depth or quantity of litter used is increased. The fresh litter material acts as a diluent for the broiler faeces. Reducing litter depth will result in a proportional increase in litter moisture, oil and nitrogen levels.

Flock health

There are several infectious and non-infectious diseases and conditions that may increase the severity of hock burn, pododermatitis and breast blisters. No one condition is likely to precipitate lesions but the presence of one or more of the following diseases and conditions combined with other known factors is cause for concern.

255

Any condition that reduces the birds mobility increases the risk of hock burn and pododermatitis. This is largely because the bird will spend more time inactive, prolonging the contact with the poor litter surface. Enteritis may be localized to the gut, eg coccidiosis. Alternatively, diarrhoea can be a clinical sign of a systemic disease, eg malabsorption syndrome (runting and stunting syndrome). In either case a bird with diarrhoea will excrete excess water and undigested fats and protein all of which will contribute to the deterioration of the litter. In the case of malabsorption syndrome the accompanying skeletal abnormalities, arthritis and stunting, will reduce the birds mobility and increase the risk of lesions.

Stocking density

Increasing the stocking density has a direct effect on the concentration of droppings in each square metre. Although high stocking densities per-se will not precipitate the condition, increasing the stocking density directly increases the risk of encountering burnt hocks and pododermatitis (Proudfoot et al., 1979, ADAS unpublished data).

Field investigations

Experimental work and data collected on commercial operations has allowed ADAS to formulate an approach to solving litter quality problems. A series of litter quality standards have been produced and these can be used to interpret data collected in field studies. By comparing the real values collected in such a study with standard curves it has become possible to determine whether a problem is likely to be due to one particular factor, or a combination of factors. Unfortunately most litter quality problems are investigated after the event and most producers in the UK do not keep extensive records of the environmental conditions or feed composition provided for each flock. Consequently, any investigation must be carried out in a subsequent flock. The information required for an assessment of the litter quality problem includes environmental, litter (litter nitrogen, litter moisture and oil contents) and feed (nitrogen and oil contents) data. The critical period in the development of litter quality problems is, in UK conditions, when the birds are between 21 and 35 days of age. However, to build a complete picture it may be necessary to collect information throughout the growing cycle.

256

Conclusion

The incidence of contact dermatitis is largely influenced by litter condition. The development of poor litter condition is a multifactorial problem relating to the housing, husbandry, and health of the stock. A panacea is not available because of the complex nature of the problem.

References

Berg, R.W., Buckingham, K.W. and Stewart, R.L., 1986. Etiologic factors in diaper dermatitis: the role of urine. Pediatric Dermatology 3, (2), 102-106.

Bray, T.S., 1985. The effects of nutrition on broiler litter condition. Pigs and Poultry 1984, Reference Book 231 (84), MAFF publications, UK Bray, T.S. and Lynn, N.J., 1986. Effects of nutrition and drinker design on litter condition and broiler performance. Br. Poult. Sei. 27, (1), 151.

Buckingham, K.W. and Berg, R.W., 1986. Etiologic factors in diaper dermatitis: the role of faeces. Pediatric Dermatology 3, (2), 107-112.

Fehlhaber, K., Bergmann, V., Scheer, J., Willsch, K. and Valentin, A., 1987. Food hygiene evaluation of skin changes on broiler carcasses. Monatshefte für Veterinaermedizin 42, (6), 206-209.

Greene, J.A., McCracken, R.M. and Evans, R.T., 1985. A contact dermatitis of broilers - clinical and pathological findings. Avian Pathol. 14, (1), 23-38.

Harris, G.C., Musbah, M., Beasley, J.N. and Nelson, G.S., 1978. Development of dermatitis (scabby-hip) on the hip an thigh of broiler chickens. Avian Dis. 22, 122-130.

Hemminga, H. and Vertommen, M.H., 1985. Faecal burnspots upon the breast skin of broiler chickens. Pluimveehouderij 15, 12-14.

Lynn, N.J. and Spechter, H.H., 1986. The effect of litter material and depth on broiler performance and aspects of carcass quality. MAFF Internal Report FAC 497.

Lynn, N.J. and Spechter, H.H., 1987. The effect of drinker type and design on broiler performance, water usage, litter moisture and atmospheric ammonia. MAFF Internal Report FAC 488.

Mahzoon, S., Yamamoto, S. and Greaves, M.W., 1977. Response of skin to ammonium persulphate. Acta Dermatovener 57, 125-126.

Martland, M.F., 1984. Wet litter as a cause of plantar podo-dermatitis leading to foot ulceration and lameness in fattening turkeys. Avian Pathol. 13, (2), 241-252.

Martland, J.F., 1985. Ulcerative dermatitis in broiler chickens: the effects of wet litter. Avian Pathol. 14, (3), 353-364.

257

Mcllroy, S.G., Goodall, E.A. and McMurray, C.H., 1986. A longitudinal survey of contact dermatitis in broilers. Proceedings of the Society for Veterinary Epidemiology and Preventive Medicine, 2-4 April 1986 (ed Thrusfield, M.V.) Edinburgh, UK, 164-173.

Page, R.K., 1974. Scabby hip disease in broilers. Poult. Digest 33, (392), 431-432. Pattison, M., 1987. Problems of diarrhoea and wet litter in meat poultry. Recent

Advances in Animal Nutrition, 1987 (ed Haresign, W. and Cole, D.J.A), 27-37. Payne, G.C., 1967. Factors influencing environmental temperature and humidity in

intensive broiler houses during the post brooding period. Br. Poult. Sei. 8 (2), 101-118.

Proudfoot, F.G., Hulam, H.W. and Ramey, D.R., 1979. The effect of four stocking densities on broiler carcass grade, the incidence of breast blisters and other performance traits. Poult. Sei. 58, (4), 791-793. Randall, C.J., Meakins, P.A., Harris, M.P. and Watt, D.J., 1984. A new skin disease in broilers. Vet. Rec. 114, (10), 246.

258

Table 1 The effect of protein quality and quantity at 2 salt levels on the moisture level (%) of the litter surface at 48 days.

Sodium (%) 0.129 0.267

Sodium (%) 0.129 0.267

Amino acid levels (lysine/methionine (%)

1.10/0.40 41.99 53.01

Good 42.54 53.64

1.26/0.45 45.50 53.55

Protein quality

Mixed 44.02 53.36

1.46/0.53 47.21 53.27

Poor 48.14 52.83

Table 2 The effect of protein quality and quantity at 2 salt levels on the nitrogen level (%) of the litter surface at 48 days.

Sodium (%) 0.129 0.267

Sodium (%) 0.129 0.267

Amino acid levels lysine/methionine (%)

1.10/0.40 5.75 5.98

Good 5.72 6.08

1.26/0.45 6.68 6.77

Protein quality

Mixed 6.43 6.60

1.46/0.53 7.25 7.48

Poor 7.53 7.55

259

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G - Good quality M — Mixed quality P - Poor quality E — Excessive A - Adequate D — Deficient H - High salt

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i — i — i — i — i — i — i — i — i — i i — r M G M G P P P G M M P P A D D A E A A E E A D E

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262

THE INFLUENCE OF DIET AND STOCKING DENSITY ON CARCASS QUALITY OF BROILERS PROCESSED UNDER SOFT- AND HARD-SCALD CONDITIONS

S.F. Bilgili, W.H. Revington, E.T. Moran, Jr., and R.D. Bushong

Department of Poultry Science and Alabama Agricultural Experiment Station, Auburn University, Alabama 36849-5416, U.S.A.

Abstract

In two experiments, a total of 2880 male broilers was reared under a 2x3 factorial arrangement of diet (DD) and stocking density (SD). Birds were provided high and low density diets under three SD (. 08, .07 and . 06 m2/bird). At 42 d, one-half of the broilers (720I experiment) were processed under either soft (53° C) or hard (59° C) scald temperatures (ST). Following slush-ice chilling (static and agitated chill in Experiment I and II, respectively) carcass yield and defects, water uptake and weepage following fresh holding and freeze-thaw were determined.

The ST significantly affected water uptake and weepage; higher for carcasses scalded at 53 °C and chilled under agitation as compared to those scalded at 59° and chilled under static conditions. Significant and linear SD effect was observed for thigh scratches and back bruises. Soft-scald temperatures and associated picking stress increased carcass defects (tears on wings and back, and broken wings). Processing variables appeared to influence the carcass quality attributes to a greater extent than the practical ranges of DD and SD utilized in this study.

Introduction

Carcass downgrading continues to exert economic losses for the broiler industry. Broiler downgrades averaged 46% in the U.S. with an estimated economic loss of $207 million in 1988 (Bilgili, 1990). Factors contributing to broiler carcass down- grading, although numerous can be classified into five broad categories; breed/strain-cross disposition, environment/management, nutrition, bird handling and processing (Bilgili, 1990). However, under commercial conditions live production and processing factors often interact to influence the incidence and severity of carcass defects. Fletcher and Thomason (1980) and Sams et al. (1990) have reported a significant impact of scalding temperatures on the appearance of oily-bird and scabby-hip syndromes, respectively. The present study

263

evaluated the influence of diet and stocking density on carcass quality attributes of male broilers processed under soft- and hard-scald conditions.

Materials and Methods

Two experiments (Exp.) were conducted (Exp. I: September 20 - November 1; Exp. II: December 27 - February 7). In each Exp. a total of 1440 male broilers was reared under a 2x3 factorial arrangement of diet (DD) and stocking density (SD). Birds were provided a high density (22.64, 20.62 and 18.62% CP and 3246, 3291 and 3335 kcal ME/kg) and low density (21.42, 19.52 and 17.71% CP and 3071, 3116 and 3160 kcal ME/kg) starter (1-21 d), grower (21-35 d) and withdrawal (35-42 d) diets, respectively, under three SD of .08, .07 and .06 m2/bird. At 42 days of age 20 birds were selected at random from each replicate pen (6 pens/DD and SD; total 36 pens), wing banded and weighed individually. Following 6 h of feed and water withdrawal (cooped) one-half of the birds were processed at the Department of Poultry Science Research Processing Plant using either soft (53 °C) or hard (59 °C) scald water temperatures for 82 sec. The birds were processed using manual exsanguination (without stunning) with 90 sec bleed-time and 45 sec picking time. The carcasses were individually weighed after final wash (hot carcass weight) and after-chilling (chilled carcass weight) which consisted of static slush-ice (24 h at 2°C) in Exp. I and agitated slush-ice (4 h at 2°C) in Exp. II. The CCW and abdominal fat weights (Exp. I, only) were obtained after 5 min of drip time. Carcass defects (bruises, scratches, tears, broken bones) were noted individually by location (wings, breast, back, thighs, drums) post-chill on all carcasses in Exp. I. Following carcass evaluations one-half of the carcasses were either fresh stored (24 h at 2°C) or frozen (7 d at -10°C) -thawed (at 2°C) to determine the extent of moisture loss (weepage).

Data from both experiments were subjected separately to analysis of variance using the General Linear Models procedure of statistical analysis system (SAS Institute, 1982). Polynominal contrasts (linear and quadratic) were used to separate effects due to SD.

Results and Discussion

The influence of DD and SD on live performance of male broilers from both experiments are summarized in Table 1. Body weights and feed efficiency was significantly affected by the DD only in Exp. I. Significant SD effect was observed for 42 d body weights (linear) in Exp. I which agrees with previous reports (Proudfoot et al., 1979; Weaver et al., 1982). Feed efficiency differences between the diets existed only in Exp. I. There was no DD*SD interaction in either experiments. The apparent live performance differences between the two experiments may be attributed to chick size (47 and 38 g for Exp. I and

264

II, respectively) due to breeder flock age differences and to much colder environmental temperatures encountered during the Exp. II.

Increasing the SD resulted in improved (linear) carcass yields (Table 2) in both experiments, indicating an optimum expression of this trait at medium placement density (Mahapatra and Mohapatra, 1989). There were no differences in abdominal fat content (both in g and percent of live weight) in Exp. I for either DD or SD (data not shown). Significant DD*SD interactions were observed for processing live weights and chilled carcass weights only in Exp. II. These interactions, which were attributed to bias in sampling birds for processing were inconsistent and did not appear as biologically meaningful.

The scald temperature (ST) treatments significantly affected percent water uptake when the carcasses were slush-ice chilled under static (Exp. I) and agitated (Exp. II) conditions. Under static slush-ice chill conditions the hard-ST (59 °C) resulted in higher moisture uptake as compared to soft-ST (53°C), whereas the converse was true for the agitated slush-ice chill. High ST results in removal of the cuticle layer and protein coagulation of the skin and hence impede water absorption during chilling (Gwin et al., 1950). Water uptake was significantly higher in birds that were soft-scalded and chilled under agitated slush-ice conditions in Exp. II, which agrees with previous observations (Thomason, 1981). A significant (P<.05) DD*ST interaction was present in Exp. II for percent water uptake. The extent of water uptake was greater under soft-ST for high density as compared to low density diets (19.5 and 17.4%, respectively). Whereas, water uptake did not differ between the two DD under hard-ST (14.9 and 14.3% for high and low DD, respectively). Essary and Dawson (1965) have reported that the extent of moisture pick-up during chilling was associated with carcass fat deposition. Diet density had no effect on abdominal fat content in Exp. I. Although not measured, it is conceivable that observed DD*ST interaction in Exp. II may be due to diet related differences in carcass fat content.

Diet, SD, ST and chilling method effects on fresh-holding and freeze-thaw weepage are summarized in Table 3. A significant and quadratic SD effect was present for fresh-holding weepage in Exp. I. The ST treatments had a pronounced effect on both fresh-holding and freeze-thaw weepage in both experiments. The nature of weepage somewhat parallel the extent of water uptake during chilling. However, in Exp. I both fresh-holding and freeze-thaw weepage exceeded moisture uptake during static chilling. This difference may be explained by additional water uptake which may have occurred during final wash (Thomason, 1981). In Exp. II, hard-ST resulted in greater frozen-thaw weepage as compared to soft scald, which agrees with previous observations (Arafa et al., 1978). Significant and linear SD (thigh scratches and back bruises) and ST (breast bruises, thigh scratches, wing tears, broken wings and back tears) effects were observed in Exp. I (Table 4). The reduction in carcass grade with increasing SD have been reported (Proudfoot et al., 1979). Thigh scratches increased linearly with increasing SD and were more prevalent under hard-ST. Proudfoot and Hulan (1985) reported similar SD effect on the incidence of

265

scabby-hip syndrome in broilers. Similarly, Sams et al. (1990) observed that soft scalding resulted in fewer scab-containing scratches than hard-ST. The linear reduction in the incidence of back bruises may be explained by a reduction in overall activity (i.e., walking, pecking and scratching) of birds under higher SD (Blokhuis and Van der Haar, 1990). The incidence of breast bruises were higher under hard-ST, possibly enhancing appearance of bruises due to loss of skin color (Heath and Thomas, 1973). Soft scald resulted in significantly higher incidence of wing and back tears and broken wings as compared to hard scald treatment. These effects are attributed to picking stress since picking efficiency was maintained when the soft-ST were used.

Diet and SD levels chosen in this study represented practical extremes utilized under commercial conditions in the U.S. Under these terms, superimposing processing treatments have significantly influenced objective as well as subjective carcass quality attributes. In the present study, processing variables (i.e., ST, chilling methods, picking severity) appeared to affect carcass quality of male broilers to a greater extent than live production variables, a finding supported by Fletcher and Thomason (1980).

References

Arafa, A.S., Wilson, H.R., Janky, D.M. and Oblinger, J.L., 1978. Quality characteristics of bobwhite quail scalded at different times and temperatures. J. Food Sei. 43, 870-873.

Bilgili, S.F., 1990. Broiler quality: grades are posted. Broiler Ind. 53, (1), 32-40. Blokhuis, H.J. and van der Haar, J.W., 1990. The effect of the stocking density on the

behavior of broilers. Arch. Geflugelk. 54, (2), 74-77. Essary, E.O. and Dawson, L.E., 1965. Quality of fryer carcasses as related to protein and

fat levels in the diet. 1. Fat deposition and moisture pick-up during chilling. Poultry Sei. 44, 7-15.

Fletcher, D.L., and Thomason, D.M., 1980. The influence of environmental and processing conditions on the physical carcass quality factors associated with oily bird syndrome. Poultry Sei. 59, 731-736.

Gwin, J.M., Pigeon, R.E., Packer, F.A., 1950. The effect of dressing temperatures of poultry on water absorption. Poultry Sei. 29, 761.

Heath, J.L. and Thomas, O.P., 1973. The xanthophyll content and color of broiler skin after scalding. Poultry Sei. 52, 967-971.

Mahapatra, CM., and Mohapatra, S.C., 1989. Effect of stock density on meat yield and quality of broilers. Indian J. of Anim. Sei. 59, (7), 903-904.

Proudfoot, F.G., and Hulan, H.W., 1985. Effects of stocking density on the incidence of scabby hip syndrome among broiler chickens. Poultry Sei. 64, 2001-2003.

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Proudfoot, F.G., Hulan, H.W., and Ramey, D.R., 1979. The effect of four stocking densities on broiler carcass grade, the incidence of breast blisters, and other performance traits. Poultry Sei. 58, 791-793.

Sams, A.R., Hargis, B.M., Hyatt, D.T., and Breger, C.R., 1990. Research Note: Scalding conditions can improve the appearance of broilers with scabby-hip syndrome. Poultry Sei. 69, 1006-1008.

SAS Institute, 1982. SAS User's Guide: Statistics. SAS Institute, Inc. Cary, North Carolina, U.S.A.

Thomason, D.M., 1981. Moisture uptake, weepage in broiler carcasses. Broiler Ind. 44, (5), 42-46.

Weaver, W.D., Jr., Beane, W.L., and Cherry, J.A., 1982. Effect of light, feeding space, stocking density and dietary energy on broiler performance. Poultry Sei. 61, 33-32.

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272

NUTRITION AND PRODUCT QUALITY

J.P. Holsheimer

Spelderholt Centre for Poultry Research and Information Services, Agricultural Research Service (DLO), 7361 DA Beekbergen, The Netherlands

Abstract

Eighteenhundred male and female broiler chicks, separated per sex, were offered a low density starter diet for the first 2 weeks. In the experimental period between 2 and 7 weeks of age five iso-energetic diets were offered. The low-fat diet 1 contained 4.4% crude fat. The high-fat diets 2 to 5 contained 11.3% crude fat which for 8% came from the inclusion of animal fat, rapeseed oil, sunflowerseed oil and coconut fat respectively. In a separate experiment the metabolizable energy values, fat and fatty acid digestibility of the experimental diets were determined. Gain per ME intake of the chicks on the low-fat diet was lower than on the high-fat diets. Energy and protein efficiency of males was better than of females and decreased by increasing age. Carcass composition and percentage fat in legs and breast meat were not affected by the dietary treatments. Male chicks had a higher percentage carcass protein and lower percentage carcass fat and leg fat than females. Fat deposition per ME intake was highest in the chicks on the high-fat diets. Dietary fatty acid composition affected the carcass fatty acid composition to a great extent. Between sexes fat composition was similar. Fat composition of legs and breast meat per dietary treatment were also similar. Lowest skin plus fat yields were obtained with the chicks on diets with rapeseed oil and sunflowerseed oil.

Introduction

Cheng et al. (1949), Renner and Hill (1961) and Young et al. (1980) found evidence that saturated fatty acids, in particular palmitic acid and stearic acid are digested less efficiently than unsaturated fatty acids. In experiments of Corino et al. (1980) and Sibbald and Kramer (1980) these findings were confirmed. Young and Garrett (1963) reported that oleic acid appears to play a direct role in facilitating the absorption of saturated fatty acids. Increasing the amount of oleic acid in relation to palmitic acid resulted in a linear increase of palmitic acid absorption.

273

There is some disagreement about the effect of dietary fat and especially unsaturated fatty acids on the quantity of body fat. Bartov et al. (1974), Griffiths et al. (1977) and Whitehead (1985) reported that addition of fat to a diet, without changing the total dietary energy content, has little influence on the quantity of deposited body fat. March et al. (1984) found that isocaloric substitution of corn oil for starch had no significant effect on the amount of abdominal fat, adipocyte numbers, or adipocyte size in chicks fed diets with 20 and 30% protein. In contrast to these reports Mickleberry et al. (1966) found that modifying the dietary lipid content resulted in a marked change in both quantity and fatty acid composition of broiler carcass lipids. The carcass fat was found to be similar in fatty acid composition to the derived fat. Abdominal fat was found to be least resistant to change, with the lipid content of the liver most resistant to change. The diets used contained 10% cerelose, corn oil, lard and coconut oil. Liver lipid was found to contain much higher levels of stearic acid and arachidonic acid and lower levels of oleic acid than abdominal lipid, regardless of the dietary treatments. O'Hea and Leveille (1969) have shown that 90 to 95% of total fatty acid synthesis occur in the liver. Further experiments of Leveille et al. (1975) and Borron and Britton (1977) confirmed these results. Leveille et al. (1975), Tanaka et al. (1983) and Donaldson (1985) reported that vegetable oils such as soybean oil are known to affect lipogenesis negatively. Yeh et al. (1970), Pearce (1974) and Whitehead (1985) reported that fat supplemented diets will depress hepatic lipogenesis. Balnave and Pierce (1969) and Infield and Annison (1973) reported that the nature of dietary fat, and in particular its linoleic acid content, may have an important influence on the control of fatty acid synthesis and desaturation in the bird. In an experiment of Bottino et al. (1970) it was found that when broilers are offered a fat-free diet, the predominant fatty acids synthesized in the course of de novo lipogenesis were the long chain fatty acids palmitic acid and oleic acid. Percentages in the fat were about 25 and 58% respectively. Bartov (1988) described that in the lipogenesis, mainly from carbohydrates, fatty acids are yielded without double bonds or with only one double bond, i.e. relatively saturated fat. The unsaturated fatty acids originated from the diets, mainly from vegetable sources and fish products and are unchanged in carcass fat. In birds given a fat supplemented diet, the carcass fat is composed of a mixture of dietary fatty acids, which are deposited without being metabolized (Salmon and O'Neil, 1973; Bartov et al., 1974), and fatty acids synthesized form carbohydrates. Salmon and O'Neil (1973) found that by increasing the dietary fat content, the deposited carcass fat closely resembles that of the dietary fat in composition of the fatty acids. Edwards et al. (1973) and Fuller and Rendon (1977) also reported that the level and degree of saturation of the added fat will influence the fatty acid composition of the carcass fat. In an experiment of Jones (1986) it is concluded that by feeding vegetable oils with high levels of unsaturated fatty acids, the broiler carcasses contained less saturated fatty acids than by feeding diets with high levels of saturated fatty acids. Whitehead and Griffin (1986) reported that by adding 5 % vegetable oil to a diet, the proportions of linoleic acid and oleic acid increased at the expense of palmitic acid, palmitoleic acid and stearic acid. Whilst greater body fatness increased the proportion of palmitoleic acid at the expense of linoleic acid.

274

The objective of this investigation was to study the distribution of fatty acids in the broilers' carcass, breast meat and legs of birds fed a low-fat diet and diets containing similar quantities of animal fat, rapeseed oil, sunflowerseed oil and coconut fat, all having a different fatty acid composition.

Materials and Methods

Eighteenhundred one day old broiler chicks, separated by sex, were housed in 120 floor pens. At 1 day of age the chicks were vaccinated against Infectious Bronchitis, at 1 week against Newcastle Disease and at 2 weeks against Gumboro. During the first 3 weeks there was continuous light, after that, a regime of 1 hour light and 3 hours dark was maintained. The first 2 weeks a low-energy starter diet with 12.13 MJ ME/kg and 12.5 g/kg lysine was offered. In the experimental period between 2 and 7 weeks 5 diets with the same ratio energy/first limiting amino acid were offered ad libitum. Diet 1 had a crude fat content of 4.4%; diets 2 to 5 had a crude fat content of 11.3% of which 8% came from animal fat, rapeseed oil, sunflowerseed oil and coconut fat respectively. A separate experiment was carried out to determine the metabolizable energy values, fat and fatty acid digestibility of the 5 experimental diets. Chick weight and food consumption was determined at 2, 6 and 7 weeks. At 2 weeks 6 males and 6 females were removed at random from 12 pens for analyses of N and crude fat of the carcasses, at 6 and 7 weeks 3 chicks per pen. At 6 and 7 weeks 3 female chicks per pen were slaughtered to determine yield. Each bird was weighed just prior to slaughter and yield was calculated as a percentage of live bodyweight (Uijttenboogaart and Gerrits, 1982). Legs and breast meat were collected for analyses of fat and fatty acids. Male birds were also collected for analyses of N and crude fat of total carcass, legs and breast meat. Per sex 10 samples of legs and 10 samples of breast meat were collected. Food was withdrawn at least 4 hours before slaughter. Data were subjected to analyses of variance using the Genstat Program (Genstat Manual, 1977).

Results

The analyses of the experimental diets are presented in Table 1. Table 2 presents the digestibility of fat and fatty acids. Gain, food intake, food/gain ratio and gain per MJ intake are presented in Table 3. In Table 4 percentages of crude protein and fat of carcasses, legs and breast meat are presented. Fat deposition figures are given in Table 5. Table 6 presents values of the fatty acids deposited in the carcasses. In Table 7 values of the analyzed fatty acids in carcasses, legs and breast meat of mixed sexes are given.

275

Differences in yields are presented in Table 8 and 9.

Discussion

Diets and fat digestibility

In the digestibility experiment it was found that the determined ME of diets 3, 4 and 5 were almost equal however, ME of diet 1 was 2% higher and of diet 2 was 5% lower than the mean value (Table 1). The differences are partly explained by the digestibility figures in Table 2, showing an equal fat digestibility of diets 3, 4 and 5 but also for diet 1. The low ME value of diet 2 is due to the low fat digestibility figure. In all diets lauric- and myristic acid were well digested, even considering the high values in diet 5 with coconut fat. In diet 1 (low-fat) and diet 5 (added coconut fat) the percentages of palmitic- and stearic acid in the fat are about the same. However, diet 1 contains 3 times more linoleic acid. This could explain the better digestibility of palmitic-and stearic acids in the high linoleic acid content in diet 1. Diet 2 (added animal fat) and diet 5 (added coconut fat) contain relatively low percentages of linoleic acid. Digestibility of the saturated fatty acids palmitic- and stearic acids in these diets are the lowest compared with the diets containing more linoleic acids. Cheng et al. (1949), Renner and Hill (1961), Young et al. (1963), Corino et al. (1980) and Sibbald and Kramer (1980) reported that the saturated fatty acids palmitic- and stearic acid are less efficiently digested compared with unsaturated fatty acids. Our findings agree with these observations with the remark that the determining factor could be the content of linoleic acid. Digestibility of oleic acid in the 5 diets was equal despite the different levels in the diets. Dietary linoleic acid values varied strongly, but did not affect the digestibility.

Performance

In the experimental period from 2 to 6 weeks, chicks on the low-fat diet 1 showed the highest gain, but also the highest food intake (Table 3). Gain per ME intake was the lowest. These differences were not found to be significant at 7 weeks. Male chicks had always a higher gain, food intake and better food/gain ratio than female chicks. Gain per ME intake was also better which means that they are more efficient growers.

276

Carcass analyses

The dietary treatments had no significant effect on the protein and fat content of the carcasses and on the fat content of legs and breast meat. Mean figures of the dietary treatments only are therefore presented in Table 4. Males had more carcass protein than females but for both sexes it did not increase between 6 and 7 weeks. Females had more carcass fat than males and this increased between 6 and 7 weeks more by females than by males. Fat content in legs of females was higher than of males. It increased for both sexes between 6 and 7 weeks. The increase in females was higher than in males. Fat content in breast meat was relatively low for both sexes.

Fat deposition in carcasses

Chicks on the low-fat diet 1 had the highest fat deposition (Table 5). No differences were found between the other 4 treatments. Fat deposition calculated per MJ intake resulted in no different fat deposition values between the low-fat diet 1 and high-fat diets 2 to 5. These findings agree with the results of Bartov et al. (1974), Griffiths et al. (1977) and Whitehead (1985). Food consumption times dietary fat content times fat digestibility shows that chicks on diet 1 absorbed 164 g fat from dietary fat. In the carcasses 358 g fat was deposited which means that at least 50% of the body fat originated from dietary carbohydrate and protein sources. Calculations of the four high-fat diets show that fat deposition in the carcass and g absorbed fat intake were nearly the same. Fat deposition per energy intake was higher in females than in males and decreased by increasing age.

Fatty acids deposition in carcasses

Considering lauric-, myristic-, palmitic-, stearic-, oleic-, linoleic- and linolenic acid, the dietary treatment had always an effect on the deposition of these fatty acids in the broiler carcass (Table 6). This agrees with findings by Edwards et al. (1972) and Fuller and Rendom (1977) that the level and composition of added fat will influence the fatty acid composition of the carcass fat. The main fatty acids in the carcass of the chicks fed the low-fat diet 1 were palmitic- and oleic acid, which confirms the findings of Bottino et al. (1970). Deposition of linoleic acid was low.

277

Diet 2 with animal fat was relatively rich in palmitic acid, oleic acid and linoleic acid. Deposition of these fatty acids in quantity were similar compared with deposition in the carcasses of the chicks on diet 1. Diet 3 with rapeseed oil contained relatively high levels of oleic acid and linoleic acid. The deposition of oleic acid in the carcasses was relatively high, but not so of linoleic acid. Diet 4 and 5 with sunflowerseed oil and coconut fat contained less oleic acid than diet 2 and 3 with animal fat and rapeseed oil. Deposition in the carcasses showed the same differences. Diet 4 with sunflowerseed oil contained the highest level of linoleic acid. Deposition of this fatty acid in the carcasses was also the highest compared with the other dietary treatments. Diet 5 with coconut fat contained high levels of lauric- and myristic acid. The carcasses contained also high levels of both fatty acids. These findings confirm the results of Salmon and O'Neil (1973) and Jones (1986) that the carcass fat resembles the dietary fat. Percentage linoleic acid in the fat of diets 2, 3 and 4 increased (Table 1). Total deposition of the saturated fatty acids in diets 2, 3 and 4 decreased (Table 6), from 79 g (diet 2) to respectively 46 and 51 g. The observations of Balnave and Pearce (1969) and Infield and Annison (1973) that desaturation of chicks is affected by increasing linoleic acid content is therefore partly true. Deposition of myristic- and linolenic acid were not different between males and females. Deposition of fatty acids in the carcasses increased between 6 and 7 weeks but was affected by the diet.

Fatty acid composition in carcasses, legs and breast meat

Diet 5 with coconut fat with high levels of short chain lauric- and myristic acid gave also high levels of these fatty acids in both carcasses, legs and breast meat (Table 7). Between the other dietary treatments, differences were small. Palmitic-, stearic- and oleic acid in carcasses of all dietary treatments were higher than in legs and breast meat. For linoleic- and linolenic acid the figures show the opposite. Legs and breast meat of all groups contained at least twice as much linoleic acid as the whole carcasses. Diet 3 with rapeseed oil gave much more linolenic acid in legs and breast meat than in the whole carcass. Legs and breast meat had the same fatty acid composition.

278

Yields

The dietary treatments had only little effect on yields (Table 8). Differences were found in griller- and skin plus fat yield. Griller yield was highest in birds fed the low-fat diet 1 and diet 5 with coconut fat. Lowest skin plus fat yields were found by birds on the diets with rapeseed oil (diet 3) and sunflowerseed oil (diet 4). Between 6 and 7 weeks, yields of edible organs, breast meat and skin plus fat increased and yields of legs, wings, neck plus neck skin and rest carcass decreased.

References

Balnave, D. and Pearce, J., 1969. Adaptation of the laying hen (Gallus domesticus) to dietary fat. Comp. Biochem. Physiol. 29: 539-550.

Bartov, L, Bornstein, S. and Lipstein, B., 1974a. Effect of calorie to protein ratio on the degree of fatness in broilers fed on practical diets. Br. Poul. Sei. 15: 107-117.

Bartov, I., Lipstein, B. and Bornstein, S., 1974b. Differential effects of dietary acidulated soybean oil soapstock, cottonseed oil soapstock and tallow on broiler carcass fat characteristics. Poult. Sei. 53: 115-124.

Bartov, I., 1988. Fats in poultry nutrition. Poult. Int. Oct.: 70,72. Borron, D.C. and Britton, W.M., 1977. The significance of adipose tissue and liver as

sites of lipid biosynthesis in the turkey. Poult. Sei. 56: 353-355. Bottino, N.R., Anderson, R.E. and Reiser, R., 1970. Animal endogenous triglycerides: 2.

Rat and chicken adipose tissue. Lipids 5: 165-170. Cheng, A.L.S., Morehouse, M.G. and Deuel, H.G., 1949. The effect of the level of

dietary calcium and magnesium on the digestibility of fatty acids, simple triglycerides and some natural and hydrogenated fats. J. Nutr. 37: 237-250.

Corino, C , Dell'orto, V. and Pedron, O., 1980. Effect of the acid composition of fats and oils on the nutritive efficiency of broiler feeds. Zootec. Vet. 2: 94-98.

Donaldson, W.E., 1985. Lipogenesis and body fat in the chick: effect of calorie-protein ratio and dietary fat. Poult. Sei. 64: 1199-1204.

Edwards, H.M., Denman, F., Abou-Ashour, A. and Nugara, D., 1973. Carcass composition studies. I. Influences of age and type of dietary fat supplementation on total carcass and fatty acid composition. Poult. Sei. 52: 934-948.

Fuller, H.L. and Random, M., 1977. Energetic efficiency of different dietary fats for growth of young chicks. Poult. Sei. 56: 549-557.

Genstat Manual, 1977. Genstat, a general statistical program. Numerical Algorithms Group, Oxford, England.

Griffiths, L., Leeson, S. and Summers, J.D., 1977. Influence of energy system and level of various fat sources on performance and carcass composition of broilers. Poult. Sei. 56: 1018-1026.

279

Infield, J.M. and Annison, E.F., 1973. The metabolism of palmitic, stearic, oleic and linoleic acids in broiler chickens. Br. J. Nutr. 30: 545-554.

Jones, R.L., 1986. Nutritional influences on carcass composition in the broiler chicken. Proc. Nutr. Soc. 45: 27-32.

Leveille, G.A., Romsos, D.R., Yeh, Y.Y. and O'Hea, E.K., 1975. Lipid biosynthesis in the chick. A consideration of site of synthesis, influence of diet and possible regulatory mechanisms. Poult. Sei. 54: 1075-1093.

March, B.E., McMillan, C. and Chu, S., 1984. Characteristics of adipose tissue growth in broiler-type chickens to 22 weeks of age and the effects of dietary protein and lipid. Poult. Sei. 63: 2207-2216.

Mickleberry, W., Rogier, J. and Stadelman, W., 1966. The influence of dietary fat and environmental temperature upon chick growth and carcass composition. Poult. Sei. 45: 313-321.

O'Hea, E.K. and Leveille, G.A., 1969. Lipid biosynthesis and transport in the domestic chick {Gallus domesticus). Comp. Biochem. Physiol. 30: 149-159.

Pearce, J., 1974. The interrelationships of carbohydrate and lipid metabolism. WPS A J. (30)2: 115-128.

Renner, R. and Hill, F.W., 1961. Utilization of fatty acids by the chicken. J. Nutr. 74: 259-264.

Salmon, R.E. and O'Neil, J.B., 1973. The effect of the level and source and of a change of source of dietary fat on the fatty acid composition of the depot fat and the thigh and breast meat of turkeys as related to age. Poultr. Sei. 52: 302-314.

Sibbald, LR. and Kramer, J.K.G., 1980. The effect of the basal diet on the utilization of fat as a source of true metabolizable energy, lipid, and fatty acids. Poult. Sei. 59: 316-324.

Tanaka, K., Ohtani, S. and Shigeno, K., 1983. Effect of increasing dietary energy on hepatic lipogenesis in growing chicks. 2. Increasing energy by fat or protein supplementation. Poult. Sei. 62: 452-458.

Uijttenboogaart, Th.G. and Gerrits, A.R., 1982. Method of dissection of broiler carcasses and description of parts. Report 370, Beekbergen, The Netherlands.

Whitehead, C.C., 1985. Influence of nutritional factors on fat in poultry, quantitatively and qualitatively. 7th Eur. Symp. Poult. Meat Qual. Vejle, Denmark: 26-35.

Whitehead, C.C. and Griffin, H.D., 1986. Development of divergent lines using plasma very low density lipoprotein concentration as selection criterion: results over the fourth generation and lack of effect of dietary fat on performance and carcass fat content. Br. Poult. Sei. 27: 317-324.

Yeh, Y.Y., Leveille, G.A. and Wiley, J.H., 1970. Influence of dietary lipid on lipogenesis and on the activity of malic enzyme and citrate cleavage enzyme in liver of the growing chick. J. Nutr. 100: 917-924.

Young, R.J. and Garret, R.L., 1963. Effect of oleic and linoleic acids on the absorption of saturated fatty acids in the chick. J. Nutr. 81: 321-329.

280

Table 1 Calculated and analyzed composition of experimental diets.

Experimental diets

Ingredients (%) Maize Maize glutenmeal (64% CP) Maizestarch Wheat Wheatbran Feedsugar Animal meal (58.2% CP) Soybean meal (49% CP) Soybean oil Animal fat Rapeseed oil Sunflowerseed oil Coconut fat Vit.min.premix Dicalcium phosphate Lime L-lysine HCl DL-methionine Coccidiostat Ethoxyquin

Calculated composition ME MJ/kg Lysine % Meth. + cyst. % Crude fat %

Analyzed composition ME MJ/kg Crude protein % Crude fat %

Analyzed fatty acids in fat (%) C8:0-C15:0 C16:0 (palmitic acid) CI8:0 (stearic acid) C18-.1 (oleic acid) C18:2 (linoleic acid) C18:3 (linolenic acid) C19:0 - C24:0

1 Low-fat

44.897 13.6

10.0

6.21 4.0

16.9 1.0

2.5

.2

.5

.13

.05

.013

13.47 1.3 1.0 4.4

14.26 23.1 5.3

1.2 13.9 4.0

29.4 46.1 3.8 1.2

2 Animal fat

35.717 4.0

11.3 7.45

4.0 26.5

8.0

2.5 .05

.2

.22

.05

.013

13.47 1.3 1.0

11.3

13.28 22.9 11.4

4.9 22.4 11.0 34.8 21.5 2.1 1.2

3 Rapeseed oil

35.717 4.0

11.3 7.45

4.0 26.5

8.0

2.5 .05

.2

.22

.05

.013

13.47 1.3 1.0

11.3

13.91 22.9 11.7

0.8 8.8 2.7

48.0 30.0 7.0 2.3

4 Sunfl.seed oil

35.717 4.0

11.3 7.45

4.0 26.5

8.0

2.5 .05

.2

.22

.05

.013

13.47 1.3 1.0

11.3

13.97 23.0 11.4

1.4 9.7 4.6

24.4 56.7

1.1 1.9

5 Coconut fat

35.717 4.0

11.3 7.45

4.0 26.5

8.0 2.5

.05

.2

.22

.05

.013

13.47 1.3 1.0

11.3

13.97 22.8 11.5

53.1 12.1 3.6

14.0 15.4 1.1 0.4

281

Table 2 Digestibility of crude fat and fatty acids (%).

Crude fat C12:0 (lauric acid) C14:0 (myristic acid) C16:0 (palmitic acid) CI8:0 (stearic acid) C18:l (oleic acid) CI8:2 (linoleic acid)

Experimental diet 1

86.1" 90.5 87.2 90.1" 80.9" 94.7 95.2"

2

75.5" 90.6 86.1 70.9b

54.2b

88.7 87.9b

3

84.0" 87.5 82.4 85.4C

78.4° 90.5 89.5"

4

85.7" 85.7 82.5 84.6C

80.3e

91.3 92.4e

5

85.9" 95.2 87.5 76.8d

66.6d

90.3 88.5b

Mean

83.4 89.9 85.1 81.6 72.1 91.1 90.7

P-value

<.05 NS NS <.05 <.001 NS <.05

a'b'c) Means of fat or fatty acid per diet bearing different superscripts differ significantly. NS means not significantly different (P>.05).

Table 3 Gain, food intake, food/gain ratio and gain per MJ intake.

Diet

1 2 3 4 5

Mean

Mean males Mean females

Gain/g 2-6 wks

1680" 1606" 1612b

1618b

1589"

1621

1764" 1477b

2-7 wks

2045

2240" 1850b

Food intake/g 2-6 wks

3052" 2966b

2881e

2890e

2875e

2933

3106" 2760b

2-7 wks

3958

4205" 371 lb

Food/gain 2-6 wks

1.82

1.76" 1.87b

2-7 wks

1.94

1.88" 2.01b

g gain per MJ intake 2-6 wks

42.1" 45.4b

44.8" 44.8b

44.1e

44.9

45.6" 44.2b

2-7 wks

41.4

42.7" 40.0b

P-valuediet <.05 NS <.05 NS NS NS <.05 NS P-valuesex <.001 <.001 <.001 <.001 <.001 <.001 <.001 <.001

Blanc space means no significant differences observed.

282

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Period in Diet

1 2 3 4 5

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weeks Fat deposition (g) 2-6 2-7

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Fat deposition (g) per MJ intake

Mean 2-6 2-7

358a

308b

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324 8.12 7.93

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286

Table 8 Significant differences in yields of female broilers (mean of 6 and 7 weeks).

Diet Griller1 Skin + fat2

1 2 3 4 5

P-value diet

71.9a

71.0C

71.5b

71.4b

71.6ab

<.05

9.1a

8.5b

8. Ie

9.4a

<.05

8.4b'

1 carcass including neck, neck skin and abdominal fat. 2 skin and fat is skin from back and breast and abdominal fat and crop fat.

Table 9 Mean yields of female broilers.

Slaughter1

Griller Edible organs Breast meat Legs Wings Neck + neck skin Skin + fat Rest carcass

6 wks

85.2 71.4 3.9 14.2 23.2 8.0 3.5 8.1

13.9

7 wks

85.6 71.6 4.4 14.5 22.5 7.8 3.3 9.3 13.6

P-value age

<.001 NS <.001 <.05 <.001 <.001 <.001 <.001 <.001

100 minus blood, feathers, head and feet.

287

288

INCORPORATING OMEGA-3 FATTY ACID INTO CHICKEN PRODUCT LIPIDS1

H.W. Hulan

Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland, A1B 3X9

Abstract

A total of 1,200 day-old Acre broiler chickens was randomly assigned to 12 pens (50 males and 50 females/pen) and divided into three blocks of four pens each. Each of four different diets was fed ad libitum to one pen of birds within each block to determine the effect of feeding practical levels of redfish meal (RFM) on the incorporation of omega-3 fatty acid into the edible meat and skin lipids of broiler chickens. The four diets included 0% (control), 4.0%, 8.0% and 12.0% RFM. Feeding diets containing RFM had no effect on overall mortality or feed efficiency but resulted in decreased incidence of Sudden Death Syndrome and lower body weight (P<.01) and feed consumption (P<.05). Additions of RFM to the diets resulted in a substantial dietary enrichment of omega-3 fatty acids (especially eicosapentaenoic acid, EPA or 20:5 o>-3, and docosahexaenoic acid, DHA or 22:6ù)-3). Analyses (wt/wt%) revealed that breast meat (less skin) was lower (PK.001) in lipid and triglyceride but higher in free cholesterol (PK.001) and phospholipid (P<.001) than thigh meat (less skin). Dietary treatment had no effect on carcass lipid content or composition. Breast meat lipid contained more (P<.001) omega-3 fatty acids (EPA, DPA and DHA), and more total omega-3 (P<.001) than thigh meat or skin. The accumulation of (Ù-3 PUFA was primarily at the expense of two omega-6 fatty acids, linoleic (18:2Ù>-6)

and arachidonic acid (20:4a-6). It can be calculated from the data presented that the consumption of 100 g of chicken that has been fed 12.0% FRM would contribute approximately 197 mg of omega-3 fatty acids (EPA + DPA + DHA) in contrast with the 138 mg of omega-3 fatty acids which would be realized from the consumption of 100 g of white fish such as cod.

'This work was carried out while the senior author was a Principal Research Scientist at the Research Station, Agriculture Canada, Kentville, Nova Scotia.

289

Introduction

The biomedical effects of fish oils have been the subject of numerous reports during the past decade (for a review see Carroll (1986), largely as a result of studies on Greenland Eskimos which revealed that these people show very little evidence of cardiovascular disease in spite of the fact that they subsist largely on a diet which is high in fat and animal protein (Bang and Dyerberg, 1980; Dyerberg, 1982, 1986). Marine animals, including seals, whales, and fish make up a relatively large proportion of this diet.

Studies have focused on the lipid portion of the Eskimo diet because of the earlier documented evidence that dietary fat can significantly influence serum cholesterol levels and atherosclerosis. Phillipson et al. (1985), Herold and Kinsella (1986) and Norum and Drevon (1986) have shown that polyunsaturated fish oils are very effective in lowering serum cholesterol levels. Furthermore, Dyerberg (1982, 1986), Herold and Kinsella (1986), Norum and Drevon (1986) have demonstrated that diets containing fish oils have an inhibitory effect on blood clotting and this reduces the risk of thrombosis, often a major factor in heart attacks and strokes. Carroll (1986) in a review on this subject, presents a possible explanation as to how fish oil consumption may result in a reduction in serum triglycerides, cholesterol and blood clotting.

Most fish lipids and other marine lipids contain very little linoleic acid (18:2o>-6) or other o>-6 fatty acids (Paul and Southgate, 1978). The main polyunsaturated fatty acids in such fats are eicosapentaenoic acid (EPA; 20:5a>-3) and docosahexaenoic acid (DHA; 22:6a>-3). Several experiments with fatty fish, a principal source of EPA in the human diet (Singer et al., 1983; Harris et al., 1983; Goodnight et al., 1982) have shown that blood platelet aggregation is reduced by such a diet or supplement and these results indicate a link to the virtual absence of cardiovascular disease among Eskimos, thought to be most probably due to EPA (Dyerberg, 1982, 1986).

Until quite recently, the only rich natural source of EPA and DHA known to man was that in products of marine origin, i.e. fish and shellfish, especially the fatty fishes (mackerel, herring, pilchard, salmon) found in the colder oceans. However, the classical studies carried out 20 years ago by Neudoerffer and Lea (1966, 1967) showed a marked increase in EPA and DHA in the edible meat lipids of turkeys with fish oil consumption. In a more recent study (Hulan et al., 1984) of the effect of different dietary fat sources on carcass fatty acid composition of broiler chickens, we observed that EPA averaged 0.13%, DHA 0.17% and DPA 0.07% of the total carcass fatty acids irrespective or dietary fat source (unpublished results). Subsequent experimentation demonstrated that the DPA came from the presence of 5% white fish meal present in all the diets fed (Lamothe, 1984). Interestingly, the latest edition (U.S. Department of Agriculture, Composition of Foods, revised August, 1979) of the Agriculture Handbook No. 8-5 lists the EPA content of almost every type of chicken product as 0.01 g 100 g"1 edible portion which is less than a tenth of the EPA available in broilers fed 5% fish meal. All commercially available fish

290

meal contains 5-11% lipid, with EPA as 9-18% of the fatty acids in the lipid (Gunstone and Wijesundera, 1978).

Fish has long been the main source of EPA and DHA in the human diet. There have been, however, major changes in the type of fish consumed in the past 100 years. For example, in the United Kingdom, per capita consumption of fatty fish has dropped from 137 g wk"1 in 1848 to 22 g wk1 in 1978 (Rice, 1984) and the calculated intake of EPA from this source has accordingly dropped from 1.7 g wk"1 to 0.2 g wk"1. In both the United Kingdom and North America, "white" fish (e.g. cod, haddock) has become the major fish type consumed, partly because of consumer preference and partly because of the poor keeping quality of fatty fish in frozen storage. White fish typically contain 0.7 g of lipid 100 g 1 and 0.1-0.2 g EPA + DHA 100 g"1 (Ackman, 1980). Usually DHA is about twice as plentiful as EPA in white fish muscle. In 1989 the per capita consumption of fish in North America was 7 kg as opposed to 28 kg of chicken. Chicken consumption in the United States was expected to reach 30 kg per capita in 1990. Considering the levels of EPA and DHA found in broilers in our preliminary experiment, and these per-capita consumption figures, it can be calculated that at least half of the EPA and DHA in the North American diet in recent years has come from the consumption of chicken. Enhancement of the EPA and DHA content of chicken could make it the main source of EPA for humans. The effect of dietary fish meal on broiler tissue a>-3 polyunsaturated fatty acids, (w-3 PUF A) has not been documented thoroughly (Dean et al., 1969). Recently, Hulan et al. (1988) demonstrated that broiler chickens fed a diet containing 5.0% fish meal have substantial amounts of EPA, DHA, and other o>-3 PUFA deposited in the total carcass and edible meat lipids, and all u-3 PUFA are significantly increased by feeding higher levels of redfish meal (15 or 30%) or redfish oil (2 or 4%).

Taste panel tests in an unpublished study found "off-flavours" in the meat of birds fed 15 or 30% redfish meal or 4.2% redfish oil. The flavors detected in these samples were not described as "fishy" or as objectionable. An experiment was undertaken to determine whether smaller and more practical amounts of redfish (Sebastes sp.) meal fed to commercial broiler chickens might increase omega-3 fatty acids in the edible meat lipid.

Materials and Methods

A total of 1,200 (600 of each sex) day-old Arbor Acre broiler chickens was randomly assigned to 12 pens, each 2.5 m x 3.25 m. The sexes were divided equally so that each pen housed 50 males and 50 females. The twelve pens were divided into three blocks of four pens each. Each diet (Table 1) was fed ad libitum to one pen of birds within each block. Diet 1 served as the control Diets 2, 3 and 4 contained 4.0, 8.0 and 12.0% redfish meal (RFM), respectively. The protein content of the RFM and diets (Table 1) was determined analytically (Association of Official Analytical Chemists, 1984). The gross

291

energy of the diets was determined by adiabatic calorimetry (Parr Instrument Co., Moline, IL, Manual No. 153). The RFM was the product of one composite batch from a reduction plant and contained 60.4% CP and 10.1% lipid.

The diets were mixed weekly and stored at 0°C. However, during the hover period, diets were fed fresh daily, whereas for the remainder of the test, feed was added to the feeders each morning from cold storage. All diets were fed in mash form.

One male and one female bird were randomly selected from each pen at 42 days, killed by exsanguination, and samples of one whole breast (both sides) and one whole thigh and skin were taken for subsequent lipid analyses. The skin was removed from the breast and thigh prior to analysis. Fat lumps attached to the skin or meat were removed and discarded before extraction to attain uniformity because this study was designed to ascertain the distribution of omega-3 fatty acids in edible portions, and excess adipose tissue was not considered as part of the edible portion. In each case the total sample (breast or thigh) was homogenized and a 100-g aliquot was taken for lipid extraction. Lipids were extracted from the tissues according to the method of Bligh and Dryer (1959).

Lipid composition was determined of these extracts by Iatroscan thin layer chromatography/flame ionization detection (TLC/FID) on a "Chromarod-SII" as previously described (Hulan et al., 1984). Rods were developed in a tank containing hexane/diethyl ether/formic acid (97/3/1, vol/vol/vol). Area percentages of peaks were converted to weight percentages using appropriate conversion factors developed with authentic standards.

A small portion of each extracted lipid sample was converted to methyl esters by transesterification with 5% BF3-MeOH (Morrison and Smith, 1964). The resulting fatty acid methyl esters were analyzed on a Sigma 3B gas Chromatograph (GC; Perkin-Elmer Co., Ltd., Montreal, Quebec) equipped with a SUPEL-COMAX-10 fused-silica capillary column (30 m x .25 mm i.d., 175 C/10 psig) and FID. The injector/detector temperatures were 200 C/260 C; the carrier gas was helium. Temperature programming was used: Temperature 1 (190 C) was held for 8 min; the temperature was then increased for 10 min. Peak areas were measured using a Perkin-Elmer LCI-100 (Perkin-Elmer Co., Ltd.) computing integrator. These areas were converted to weight percentages using a computer program that incorporated the appropriate FID response factors for all of the fatty acids (Ackman and Eaton, 1978).

The total fatty acids of the diets were recovered by direct saponification with KOH/ethanol in the presence of an added internal standard, heptadecanoic acid (Serdary Research Laboratories Inc., London, Ontario). The internal standard was used to calculate the fatty acid composition expressed as milligrams of fatty acid/100 g diet. About 20 g of the diet was accurately weighted into a 250-mL round-bottom flask. To this was added 20 mg of accurately weighted internal standard. This mixture was saponified by refluxing for

292

2 h with 2 mL of 50% KOH and 25 mL of 96% ethanol. The unsaponifiable matter was extracted before fatty acid recovery according to the American Oil Chemists Society (1983) method. Fatty acids were converted to methyl esters and analyzed by the GC as described above.

An ANOVA was calculated on pen means according to the split-plot design for complete blocks (Snedecor and Cochran, 1980). The sum of squares for diets (the main plot factor) was partitioned into a set of orthogonal contrasts: control vs. RFM, linear, and quadratic polynomial regression components on the nozero levels of RFM in diet. The subplot factor (sex) interaction sums of squares with diets was partitioned by the same set of orthogonal contrasts.

For the analysis of the composite meat samples, the full factorial ANOVA was calculated; the four-factor interaction mean square was used as the error term for testing the significance of the main effects and lower order interactions. Diet effects were partitioned by the same orthogonal contrasts as the performance traits.

Results and Discussion

The composition of the diets is given in Table 1. The RFM was incorporated into the diets primarily at the expense of soybean meal. The diets were essentially kept isoenergic (3,075 kcal/kg AME) and isonitrogenous (22.0% CP) by making necessary adjustments in the amount of corn (wheat), poultry grease, and dibasic calcium phosphate resulting from the formulation of the diets by linear programming. Substitution of wheat for corn was confounded with the fish meal addition among the 4, 8, and 12% RFM levels.

The major and selected nutritionally important fatty acids of chicken diets expressed as milligrams per 100 g of diet are given in Table 2. Diets 1 and 2 were slightly enriched with w-o PUF A, especially that of 18:2o)-6, which is derived mainly from the corn and soybean meal, but in part from the poultry grease. The control (Diet 1) showed nutritionally important amounts of a>-3 PUFA (EPA or 20:a)-3; DPA or 22:5Ü)-3; and DHA or 22:6u-3), also derived from poultry grease. The major w-3 PUFA, however, was 18:3oo-3, derived mainly from soybean meal. The total of u>-3 PUFA in the diets was comparatively low; Diet 4 showed the largest amounts of EPA and DHA in proportion to the fish meal in the diet.

There was a significant (P<.05) deviation from the linear response for diet x sample (meat) for total lipid (Table 3). To assess the effect of RFM on the total lipid deposition in breast, thigh, and skin, logarithmic transformation was taken prior to analysis to stabilize the variance among the different deposition levels. The SE are expressed as a percentage of the means. Lipid content of the breast was .9%, of thigh meat, 2.2%; and

293

of skin, 30.6%. The RFM fed at 8% generally gave higher lipid levels than when fed at 4 or 12%. Additions of RFM did not significantly change the lipid levels in breast meat or in thigh meat over those of their respective controls, but increased the level in the skin. Breast meat contained less (P<.001) total lipid and triglyceride (TG) but more (P<.001) free cholesterol (CH) and PL than did thigh meat, confirming an earlier observation (Hulan et al., 1988). Lipids associated with the skin were made up entirely of TG.

Lesser amounts (P< .001) of saturated fatty acids but greater amounts (P< .05) of omega-3 PUFA were found in female carcass lipids (Table 4). Compared with thigh meat lipids, breast meat lipids contained more (P<.001) total saturates, w-6 PUFA, o>-3 PUFA, and total PUFA, but a lower level (P<.001) of total monoenes. Similar relationships were found for thigh and skin. Additions of RFM to the diet resulted in a linear (P<.001) increase in total saturates, monenes, and a>-3 PUFA and a linear (P< .001) decrease in w-6 PUFA and total PUFA as previously reported (Hulan et al., 1988).

Edible meat lipids of female broilers contained more (P<.05) 18:3«-3 and 22:o>-3 than edible meat lipids of males (Table 5). Lipids associated with breast meat contained less (P<.001) 18:3o)-3, but more (P<.001) 20:4<o-6, 20:5a>-3, 22:5^-3, and 22:6a>-3 than lipids associated with thigh meat. Similar differences were observed between thigh meat and skin. Additions of RFM to the diet linearly (P<.001) decreased 18:2w-6, 18:3a>-3, and 20:4o)-6, but linearly (P<.001) increased the omega-3 PUFA (20:5w-3, 22:5OJ-3, and 22:6&>-3) of the edible meat lipids.

In chickens, as well as in many other animals, long-chain PUFA are usually concentrated in the PL and to a lesser extent in neutral lipids (Marion and Woodroof, 1965; Hulan et al., 1988). Of the three edible tissues studies, the PL content was greater (P<.001) in breast meat than in thigh meat; skin was devoid of this lipid class (Table 3). The higher proportion of TG in the lipid of skin tissue resulted in total fatty acids that were richer in monoenes (Table 4) and poorer in PUFA of both types, than the fatty acids of breast lipid. The level (wt/wt %) of the omega-3 fatty acids-EPA (20:5a>-3), DPA (22:5a>-3), and DHA (22:6w-3)-in lipids associated with breast meat was at least double that of thigh meat lipids (Table 5), and DHA exceeded EPA in both breast and thigh meat lipids by a factor of two or more.

For human dietary considerations, it can be calculated from the data presented in Tables 3 to 5 that an average meal of 100 g (without skin) of chicken would contain 10.7% lipid and 46.2% PL (Table 3). Assuming 70% fatty acid containing 1.51% EPA, 1.17% DPA, and 3.00% DHA (Table 5), chicken that had been fed 12.0% RFM would contribute 52.3 mg EPA, 40.5 mg DPA, and 103.8 mg of DHA for a total of 196.6 mg of these three omega-3 PUF As. Cod flesh, for comparison, based on the data of Addison et al. (1968), contains .6% lipid, with about 70% PL estimated to be 70% fatty acids or 294 mg/100 (100 g x .006 lipid x .70 PL x .70 FA). The EPA and DHA are 17 and 30% of these fatty acids, so the total for these two a>-3 PUFA will then be about 138 mg/100 g fish,

294

made up 50 mg EPA (294 x .17) and 88 mg DHA (294 x .30), as DPA is so low as not to be a factor (Ackman, 1980). In the definitive 20-yr study of Kromhout et al. (1985), eating fish three times a week or a mean intake of approximately 150 mg of EPA/day reduced cardiovascular mortality by 50%.

Both thigh and breast lipids showed moderate amounts of DPA (Table 5). This fatty acid occupies an intermediate position in the interconversion of EPA and DHA, and is possibly a temporary storage form for these two fatty acids (von Schacky and Weber, 1985). Von Schacky and Weber suggested that DPA might be included in the potential health benefits of 60-3 PUFA. Not only did DPA in chicken meat lipids increase (P<.001) with increasing RFM in the diet, but the RFM dietary proportions relative to EPA or DHA (Table 2) were substantially augmented in broiler total fatty acids (Table 5). Chicken lipid fatty acids can be made to more closely resemble those of the seal-rich diet of the Eskimo than the fish lipids now in vogue (Ackman, 1988).

The increase of oo-3 PUFA in the tissues with increasing amounts of fish meal in the diet was at the expense of co-6 PUFA. It is apparent from the fatty acid profile in Table 5 that an inverse relationship exists between the distribution of these two classes of PUFA; in general, the accumulation of a>-6 PUFA in the tissues reflects the levels of these PUFA in the diet. The all-vegetable-protein diet (Diet 1) contained the largest amount of w-6 PUFA (primarily 18:2a>-6) whereas the high fish content diet showed smaller amounts of this fatty acid, with about the same 20:4a>-6 content. Others (Mohrhauer and Holman, 1963: Miller et al., 1967a, 1969) have demonstrated that fatty acids of the oi-3 family interfere with the synthesis of 20:4oo-6 from 18:2&J-6. The data presented here are consistent with the finding of these investigators.

From the data presented, it is concluded that the edible meat of chickens fed a diet containing 8% RFM contains amounts of co-3 PUFA, comparable to those provided by white fish muscle (Addison et al., 1968; Ackman, 1986). Therefore, consumers could benefit from chicken meat enriched in these acids via the addition of more fish meal to the diets. Chicken could become a supplemental or alternative source of o>-3 PUFA. Compared with the well-publicized fish and shellfish sources, chicken is popular, free of religious limitations, and already freely consumed world-wide.

References

Ackman, R.G., 1980. Fish Lipids, Part I. Pages 86-110 in: Advances in Fish Science and Technology. J.J. Connell, ed. Fishing News Books Ltd., Farnham, UK.

Ackman, R.G., 1986. Perspectives on eicosapentaenoic acid (EPA). o>-3 News 1:1-4.

295

Ackman, R.G., 1988. Some possible effects on lipid biochemistry of difference in the distribution on glycerol of long chain (u-3) fatty acids in the fats of marine fish and marine mammals. Atherosclerosis 7:171-173.

Ackman, R.G., and Eaton, C.A., 1978. Some contemporary applications of open-tubular gas-liquid chromatography in analyses of methyl esters of longer-chain fatty acids. Fette Seifen Anstrichm. 80:21-37.

Addison, R.F., Ackman, R.G., and Hingley, J., 1968. Distribution of fatty acids in cod flesh lipids. J. Fish Res. Board Can. 25:2083-2090.

American Oil Chemists Society, 1983. Official and Tentative Methods. Tentative method ca 66-53. 3rd ed. Am. Oil Chem. Soc., Champaign IL.

Association of Official Analytical Chemists, 1984. Methods of Analysis. 14th ed. Assoc. Off. Anal. Chem., Washington, DC.

Bang, H.O. and Dyerberg, J., 1980. Lipid metabolism and ischemic heart disease in Greenland Eskimos. Adv. Nutr. Res. 3:1-22.

Bligh, E.C. and Dyer, W.J., 1959. A rapid method of total lipid extraction and purification. Can. J. Biochem. Physiol. 37:911-917.

Carroll, K.K., 1986. Biological effects of fish oils in relation to chronic diseases, Lipids 21:731-732.

Dean, P.W.F., Aitken, Lamoreux, J.R., and Proudfoot, F.G., 1969. Flavor associated with fish meal in diets fed to broiler chickens. Can. J. Anim. Sei. 49:11-15.

Dyerberg, J., 1982. In S.M. Barlow and M.E. Standsby, eds. Nutritional evaluation of long-chain fatty acids in fish oil. Academic Press, New York. pp. 245-261.

Dyerberg, J., 1986. Linolenate-derived polyunsaturated fatty acids and prevention of atherosclerosis. Nutr. Rev. 44:125-134.

Edwards, H.M., Jr., and May, K.N., 1965. Studies with menhaden oil in practical-type broiler rations. Poultry Sei. 44:685-689.

Goodnight, S.H., Jr., Harris, W.S., Connor, W.E., and Illingsworth, Dr. R., 1982. Polyunsaturated fatty acids, hyperlipidemia and thrombosis. Arteriosclerosis 2:87-113.

Gunstone, F.D. and Wijesundera, R.C., 1978. The component fatty acids of the lipid in four commercial fish meals. J. Sei. Food Agric. 29:28-32.

Harris, W.S., Connor, W.E. and McMurray, M.P., 1983. The comparative reductions of the plasma lipids and lipoproteins by dietary polyunsaturated fats: salmon oils vs vegetable oils. Metabolism 32:179-184.

Herold, P.M., and Kinsella, J.E., 1986. Fish oil consumption and decreased risk of cardiovascular disease: a comparison of findings from animal and human feeding trials. Am. J. Clin. Nutr. 43:556-598.

Hulan, H.W., Proudfoot, F.G., and Nash, D.M., 1984. The effects of different dietary fat sources on general performance and carcass fatty acid composition and broiler chickens. Poultry Sei. 63:324-332.

Hulan, H.W., Ackman, R.G., Ratnayake, W.M.N., and Proudfoot, F.G., 1988. Omega-fatty acid levels and performance of broiler chickens fed redfish meal or redfish oil. Can. J. Anim. Sei. 68:543-547.

296

Kromhout, D., Bosschieter, E.B., Coulander C. de L., 1985. The inverse relation between fish consumption and 20-year mortality from coronary heart disease. N. Engl. J. Med. 312:1205-1209.

Lamothe, F.A., 1984. The transfer of eicosapentaenoic acid in nutrition. M.Sc. Thesis, Technical University of Nova, Halifax, Nova Scotia. 161 pp.

Marion, J.E., and Woodroof, J.G., 1965. Lipid fractions of chicken broiler tissues and their fatty acid composition. J. Food Sei. 30:38-43.

Miller, D., Leong, K.C., and Smith, P., Jr., 1969. Effect of feeding and withdrawal of menhaden oil on the a>6 fatty acid content of broiler tissues. J. Food Sei. 34:136-141.

Mohrhauer, H., and Holman, R.T., 1963. Effects of linolenic acid upon the metabolism of linoleic acid. J. Nutr. 81:67-74.

Morrison, W.R., and Smith, L.M., 1964. Preparation of fatty acid methylesters and dimethylacetals from lipids with boron trifluoride-methanol. J. Lipid Res. 5:600-608.

Neudoerffer, T.S. and Lea, C.H., 1966. Effects of dietary fish oil on the composition and stability of turkey depot fat. Br. J. Nutr. 20:581-594.

Neudoerffer, T.S. and Lea, C.H., 1967. Effects of dietary polyunsaturated fatty acids on the composition of the individual lipids of turkey breasts and leg muscle. Br. J. Nutr. 21:691-714.

Norum, K.R., and Drevon, CA., 1986. Dietary a>-3 fatty acids and cardiovascular diseases. Arteriosclerosis 6:352-355.

Paul, A.A., and Southgate, D.A.T., 1978. In McCance and Widdowson's The Composition of foods. 4th ed. Elsevier/North Holland Biomedical Press, Amsterdam, The Netherlands, pp. 297-299.

Phillipson, B.E., Rothrock, D.W., Connor, W.E., Harris, W.S., and Illingsworth, D. R., 1985. Reduction of plasma lipids lipoproteins and apoproteins by dietary fish oils in patients with hypertriglyceridemia. New Engl. J. Med. 312:1210-1216.

Rice, R.D., 1984. The effect of low doses of Max EPA for long periods. Br. J. Clin. Practise 38(5) Symp. Suppl. No. 31. 85-88.

Schacky, C. von, and Weber, P.C., 1985. Metabolism and effects on platelet function of the purified eicosapentaenoic and docosahexaenoic acids. J. Clin. Invest. 76:2446-2450.

Singer, P., Jaeger, W., Wirth, M., Voigt, S., Naumann, E., Zimontkowski, S., Hadju, L, and Oedicke, W., 1983. Lipid and blood pressure lowering effect of mackerel diet in man. Atherosclerosis 49:99-108.

Snedecor, G.W., and Cochran, W.G, 1980. Statistical Methods. 7th ed. Iowa Stat Univ. Press, Ames, IA.

U.S. Department of Agriculture, 1979. Composition of foods. Poultry products, raw, processed, prepared. Agriculture handb. no. 805. USDA, Science and Education Administration, Washington, D.C. p. 56. (NDB No. 05030).

297

Table 1 Composition of diets fed.

Redfish meal (%)

Ingredient 0 4 8 12 g/kg

Ground yellow corn Ground wheat Soybean meal (49% CP) Redfish meal (RFM 60% CP Poultry grease Salt (NaCl) Ground limestone Dibasic calcium phosphate Vitamin-mineral premix1

DL-Methionine L-Lysine HCl

Analysis Protein, % Gross energy, kcal/kg

504.5 50.0

349.3

47.9 3.8

17.4 13.2 10.0 2.8 1.1

21.78 4,112

552.9 50.0

291.4 40.0 30.9 2.9

13.1 6.5

10.0 2.3

22.21 4,081

38.4 657.0 165.0 80.0 37.0 2.2 8.3

10.0 2.1

22.34 4,132

6.7 722.3 103.2 120.0 30.0

1.3 4.8

10.0 1.7

21.93 4,127

'Supplied per kilogram of diet: 10,000 IU vitamin A, 2,000 ICU vitamin D3, 8 mg riboflavin, 15 mg d-calcium pantothenate, 15 ng vitamin B12, 4 mg menadione sodium bisulfite, 35 mg niacin, 2 mg folic acid, 20 IU vitamin E, 1,000 mg choline, 300 ^g biotin, 5 mg pyridoxine*HCl, 3 mg thiamine, 187.5 mg amprolium, 200 mg ethoxyquin, 80 mg manganese, 70 mg zinc, 8 mg copper, 90 mg iron, 350 ^g idoine, 100 ug selenium.

298

Table 2 Major and nutritionally important fatty acids of chicken diets.

Fatty acid1

Saturates

Monoenes

18:2o>-6 18:3(0-3 20:4a.-6 20:5o>-3 (EPA) 22:5^-3 (DPA) 22:6o>-3 (DHA)

u-6 PUFA 0--3 PUFA

PUFA Total FA, g/100 g diet

0

1,1811.5

3,103.9

2,661.9 149.9 19.9 10.4 6.4

15.9

2,714.3 196.2

2,932.3 7.84

Redfish meal {%) 4 8 (mg/100 g of (diet)

1,328.4

2,173.9

2,139.8 114.5 13.2 37.4 7.8

47.0

2,173.3 221.7

2,405.2 5.91

1,501.0

2,501.3

1,748.5 124.9 18.0 57.8 10.6 69.0

1,785.1 284.8

2,092.4 6.09

12

1,477.9

2,503.5

1,871.8 146.1 18.1

102.8 14.9

108.6

1,910.7 404.8

2,335.8 6.32

'EPA = Eicosapentaeonic acid; DPA = docosapentaenoic acid; DHA = docosahexaenoic acid; PUFA = polyunsaturated fatty acids; FA = fatty acids

299

Table 3 Effect of different dietary levels of redfish meal (RFM) on the lipid content and composition of broiler chickens.

Source of variation

Sex Male Female SEM

Sample Breast Thigh Skin SEM

Diet 0% RFM

4.0% RFM 8.0% RFM

12.0% RFM SEM

ANOVA, level of significance Sex Sample Diet

Contrasts within diets RFM Linear Deviations4

Total lipid

11.6 10.8 (2.8%)2

0.9 2.2

30.6 (3.5%)

10.2 11.1 12.8 10.7 (4.1%)

NS *** NS

NS NS

*

Lipid composition1

TG (wt/wt %)

52.4 57.0 2.00

36.6 72.8

(100.0)3

2.00

59.2 52.1 56.0 51.5 2.83

NS *** NS

NS NS NS

CH

1.65 1.69 .134

2.42 0.92 tr 0.134

1.66 1.68 1.52 1.83 .190

NS *** NS

NS NS NS

PL

45.7 41.1

1.95

60.6 26.2 tr 1.95

39.1 46.0 42.0 46.2 2.76

NS *** NS

NS NS NS

:Trace amounts (<.05%) of cholesterol esters were found in all samples. TG = triglyceride; CH = free cholesterol; PL = phospholipids; tr = trace amount (< .05). 2SEM expressed as percentage of mean. 3Lipids associated with the skin consisted entirely of TG with only trace amounts (< .01) of diglycerides (DG), cholesterol esters (CE), CH, and PL detected; therefore the data for skin was not included in the analysis. 4Principally due to the deviation effects of RFM on the diet x sample interaction (% SEM = 7.0%): results were for breast, .88, .95, .91, and .86; for thigh, 2.77, 1.95, 2.25, and 2.20; for skin, 26.87, 30.26, 35.10, and 29.20, for dietary RFM inclusion levels of 0, 4, 8, and 12%, respectively.

*P<.05. ***P<.001.

300

Table 4 Effect of different levels of redfish (RFM) on selected classes of fatty acids (FA) in broiler chickens.

Source of variation

Sex Male Female SEM

Sample Breast Thigh Skin SEM

Diet 0% RFM

4.0% RFM 8.0% RFM 12.0% RFM

SEM ANOVA, level

of significance2

Sex Sample Diet

Contrasts within diets RFM Linear

Saturates

34.0 33.0

.18

34.3 33.4 32.8

.22

31.3 33.5 34.3 34.9

.25

*** *** ***

*** ***

Monoenes (wt/wt %

42.5 42.9

.37

36.1 42.3 49.7

.45

41.5 41.7 43.4 43.8

.52

NS #*# ***

** ***

w-6 PUFA total FA)

18.7 18.9

.22

21.3 19.7 15.4

.27

23.7 20.4 16.4 14.7

.31

NS **# ***

*** ***

0.-3 PUFA

4.8 5.3

.16

8.3 4.7 2.1

.20

3.5 4.5 5.6 6.5 .23

* #** ***

*** ***

PUFA1

23.5 24.2

.34

29.7 24.4 17.5

.42

27.3 24.8 22.0 21.3

.48

NS NS #**

*** ***

'PUFA = Polyunsaturated fatty acids. 2No significant deviations or interactions were found.

*P<.05. **P<.01.

***P<.001.

301

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302

QUALITY OF BROILERS FOR FAST-FOOD DEEP-FAT FRYING: EFFECTS OF STRAIN, SEX, LIVE PRODUCTION PROCEDURE, AND LOCATION IN THE FLOCK POPULATION

E.T. Moran, Jr., N. Acar, W.H. Revington and S.F. Bilgili

Poultry Science Department and Alabama Agricultural Experiment Station, Auburn University, Alabama 36849-5416, U.S.A.

Abstract

Peterson x Arbor Acres (PxAA) and Ross x Ross (RxR) broilers were reared sexes-separate and combined to ages that would maximize carcass numbers in the 1077-1163 g weight range (41 days for males, 47 days for females and 44 days combined sexes). All birds received common feed and management. Final live weight was greater with PxAA than RxR; however, percentages of chilled carcass yield and residual fat in the body cavity for the whole populations in each pen were to the converse. Females had more abdominal fat than males.

Each pen's population was separated into top, middle and bottom thirds by weight of total parts to evaluate the significance of location. Strain differences in carcass yield, abdominal fat, and percentages of parts with a "9-piece cut" were not detected when the populations were divided. Chilled yield upon processing, abdominal fat, and the proportions of keel-cut breast and thighs all decreased as carcass weight within the population decreased, respective of sex. Strain source did not alter carcass quality for fast-food as much as sex, then males were preferred to minimize fatness. Marketing each sex 'such that carcasses within the desired weight range would come from the upper half of the flock was of advantage to the yield of high meat parts.

Introduction

A large part of the poultry industry's expansion in the US can be attributed to the increased needs for fast-food. Broilers intended for deep-fat frying are grown to ages that would maximize weights within a specific range (the "drop-out" range). Sex-separate rearing best accomplishes this need, but errors in marketing time can greatly increase the proportions of either under- or overweight carcasses. Mix-sex flocks cannot attain as high a proportion in the "drop-out" range because males and females have a bimodal weight distribution in the population, however, errors in marketing are not as acute.

303

Low carcass fat is of advantage in extending usage of cooking fat during product preparation (Moran, 1979). Body fat is known to increase with age, and females have more extensive depots than males. Expression of fatness can readily be influenced by genetics, in turn, strain sources can differ in this respect (Griffiths et al., 1978; Joubeit and Gregorowski, 1988). Cutting of the carcass is usually done to minimize size differences among parts, and consistency in this respect is important. Chilled carcass yield from the live bird increases with age as does the proportion of breast and thighs at the expense of appendages (Moran and Orr, 1969). Again, expression of these changes can be modified by strain (Moran and Orr, 1970).

In the present study, two commercial broiler strains known to differ in live performance were reared sexes-separate and combined to ages used in practice that maximize the number of carcasses in the drop-out weight range. Separating each pen's population into top, middle and bottom portions by carcass weight permitted evaluations of strain, sex, method of live production, and location in the flock as factors in quality for fast-food purposes.

Materials and Methods

Chicks from a commercial hatchery derived from 41 week old Peterson x Arbor Acres (PxAA) and Ross x Ross (RxR) breeder flocks were placed in floor pens of an open-sided house having temperature controlled curtains. The males and females were both separated and combined (50 birds/pen; 0.07 m2/bird; 10 replicate pens for each strain and rearing treatment; 3000 total birds). All birds received common feeds that were formulated to attain NRC (1984) specifications using corn, soybean meal, corn gluten meal, and fat as primary ingredients (0-3 weeks of age: 23% protein and 3200 kcal ME/kcal; 3-6 weeks: 20% and 3200 kcal; 6 weeks-market: 18% and 3200 kcal). Males and females reared separately were processed at 41 and 47 days of age, respectively, while an intermediate period of 44 days was designated for the combined sexes. Feed and water were ad libitum. Lighting was continuous. Experimentation ensued during the summer months of August and September.

Feed and water were accessible at the time of final weighing, then birds were held in shipping crates without the stresses of live haul until processing (ca. 12 h). On line processing was done at the University Research Farm (90 sec. bleed time; 80 sec. scald at 62°C; 40 sec. picking; ca. 6 min. from rehanging the carcass through automatic evisceration until chilling). Carcasses were placed in slush ice for ca. 3 hours, then each one was drained ca. 3 min. before weighing and removal of remaining depot fat in the abdominal cavity. A "nine-piece cut" as described by Hudspeth et al. (1973) was the basis of carcass separation (i.e. wings with part of the breast, breast with entire keel, split

304

breast associated with the rib cage and having the thoracic back, drumsticks severed from the thigh through the upper femoral epiphysis, and thighs with split back). Cutting of all carcasses was done by the same person and occurred between 5 and 10 hours after processing.

Treatments were evaluated by analysis of variance on the respective data as a factorial arrangement of the main factors. Turkey's multiple range testing was employed to measure differences among either three or more comparisons.

Results and Discussion

Chick weights at the initiation of experimentation were heavier with PxAA than RxR even though all eggs were from the same age of breeders and incubated together (Table 1). PxAA continued to have a body weight advantage at 3 weeks of age and when the respective rearing treatments were marketed. No differences between strains in feed conversion could be detected.

Final live body weights among the sexes-separate and combined treatments were all heavier at their respective ages when marketed than would optimize numbers specified for fast-food needs (1077-1163 g without neck, giblets and adhering abdominal fat). Such error is to be expected in practice and determines whether carcasses in the "drop-out" category may largely come from either the top, middle or lower portions of any one flock. Although RxR had advantages in the percentages of chilled carcass yield and abdominal fat that compensated for the greater weights of PxAA while live (Table 1), these differences observed on a whole population basis could not be statistically verified when analyses examined sub-population effects (Table 2).

Location of the carcass within the pen's population, respective of sex, had substantial influence on processing yield and extent of fatness (Table 2). As weight of total parts from birds in any one pen decreased, so also did the percentages of carcass yield and abdominal fat. Males reared together with females did not express this reduction in carcass yield to the same extent as females (Table 3). Conversely, abdominal fat decreased to greater extent with females reared separate to 47 days of age than did males marketed at 41 days while response of the sexes together at 44 days was similar.

The proportions of parts in a nine-piece cut did not differ between the two strains when location of each carcass in the pen population was considered (Table 4). Boukamp et al. (1973) also examined yield of parts with two commercial strains only an eight-piece cut was used as the basis for carcass separation. Although the strains differed in the proportions of breast, wings and drumsticks when taken as averages for the entire populations, these differences were not measurable when carcasses within 100 g weight ranges were compared.

305

Percentages of the parts were markedly altered by location of the carcass in the pen population (Table 4). Contributions of keel-breast and thighs decreased as weight of the total parts decreased while wings, drumsticks and split breast increased. These changes with drumsticks and split breast occurred to a greater extent with males than females when both sexes had been reared together and marketed at an intermediate age compared to when each was separate (Table 5).

Evaluation of strain and population effects in present experimentation is statistically appropriate, however, the comparisons involving rearing procedures are unavoidably confounded by possible unequal circumstances during each of the 3 days of processing and cutting. Present observations are expected to largely reflect the effects of rearing treatments because machinery and people performing each facet of production and processing were constant.

References

Boukamp, E. L., Bigbee, D. E., and Wabeck, C. J., 1973. Strain influences on broiler parts yield. Poultry Sei. 52, 1517-1523.

Griffiths, L., Leeson, S., and Summers, J. D., 1978. Studies on abdominal fat with four commercial strains of male broiler chickens. Poultry Sei. 57, 1198-1203.

Hudspeth, J. P., Lyon, C. E., Lyon, B. C , and Mercuri, A. J., 1973. Weights of broiler parts as related to carcass weight and type of cut. J. Food Sei. 38, 145-150.

Joubert, J. J., and Gregorowski, J. J., 1988. A comparison of slaughter characteristics of different commercial broiler strains, pp. 406-408. Proc. Eighth World's Poultry Sei. Assoc. Mtg., Nagoya, Japan.

Moran, E. T., Jr., 1979. Carcass sex and finish effects on pressurized dee-fat frying of broiler chickens. Proc. Poultry Sei. Assoc. Mtg., University of Florida, Gainesville.

Moran, E. T., Jr., and Orr, H. L., 1969. A characterization of the broiler chicken as a function of sex and age: Live performance, processing, grade and cooking yields. Food Technol. 23, 91-89.

Moran, E. T., Jr., and Orr, H. L., 1970. Influence of strain on the yield of commercial parts from the chicken broiler carcass. Poultry Sei. 49, 725-729.

National Research Council (NRC), 1984. Nutrient requirements of poultry. National Academy Press, Washington, D.C.

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Table 2 Yield and abdominal fat from carcasses having the weight of total parts distributed from the top, middle and bottom thirds of the population with broilers reared sexes separate and combined to attain similar weights for fast-food use1.

Pen carcass weight distribution

Top Middle Bottom SEM

Probability Sex (age) Distribution Interaction

% Carcass [Sex (age ; M(41D)

64.9bcd

63.7b

61.5"

yield2

at marketing)]4

C(44D)

65.7cde

65.3bcd

63.7b

0.58

* *** **

F(47D)

67.3e

66.1de

64.1bc

% Abdominal fat3

[Sex (age M(41D)

2.6ab

2.5ab

2.0s

at marketing)]4

C(44D)

2.5ab

2.6ab

2.5ab

0.04

*** ** *

F(47D)

3.4C

3.2bc

2.6ab

1 Experimentation involved 10 replicate pens of 50 birds/pen for each of two strains (Peterson x Arbor Acres and Ross x Ross) and three rearing treatments. Approximately 15-16 carcasses represented each weight distribution per pen. No significant strain differences (P>.05) occurred when statistical analysis included variance associated with the separation of pen population into parts nor were there interactions with the other main factors (P>.05), thus, data for both strains were combined. SEM has 2571 df.

2 Chilled carcass without giblets and neck as a percentage of the full-fed live weight. 3 Fat removed from the body cavity as a percentage of the chilled eviscerated weight. 4 M(41D) = males reared sex-separate to 41 days of age; F(47D) = females reared

sex-separate to 47 days; C(44D) = combined sexes reared to 44 days. a e Values, respective of measurement, not having a common letter are different

(P<.05). *P<.05. **P<.01. ***P<.001.

308

Table 3 Yield and abdominal fat from carcasses having the weight of total parts distributed from the top, middle and bottom thirds of the population with broilers reared sexes mixed to 44 days of age: evaluation of males and females1.

Pen carcass weight distribution

Top Middle Bottom SEM

Probability Sex Distribution Interaction

% Carcass yield2

Males

65.3a

64.9" 63.7"

0.68

NS *** **

Females

67.6b

65.4a

63.6a

% Abdominal fat3

Males

2.7 2.5 2.2

0.20

* ** NS

Females

2.9 2.7 2.5

1 Values are from 10 replicate pens of 50 birds/pen (25 male and 25 female) for each of two strains (Peterson x Arbor Acres and Ross x Ross). Approximately 7-8 carcasses represented each weight category and sex per pen. No significant strain differences occurred when statistical analysis included variance associated with the separation of pen population by weight, respective of sex, nor were there interactions of strains with the other main factors (P> .05), thus, data for both strains were combined. SEM has 822 df. Chilled carcass without giblets and neck as a percentage of the full-fed live weight. Fat removed from the body cavity as a percentage of the chilled eviscerated weight. Values not having a common letter are different (P< .05).

NS = non-significant, P>.05. *P<.05. **P<.01. ***P<.001.

2

3

a-b

309

Table 4 Proportion of parts with a "nine-piece cut" from carcasses having the weight of their total distributed in the top, middle and bottom thirds of the population with broilers reared sexes-separate and combined to attain similar weights for fast-food1.

Factor

Sex (Age)2

M(41D) C(44D) F(47D)

Distribution Top Middle Bottom SEM

Wings

** 15.4"b

15.0b

15.9"

***

15. lb

15.4"b

15.9" 0.18

% of total Drum­sticks

*** 18.2" 17.7b

16.9C

*

17.5b 17.5b

17.9" 0.15

"nine-piece cut" Keel-breast

* 22.3" 21.9ab

21.lb

#*#

22.9" 22.2" 20.2b

0.80

Split breast

*** 17.0b

18.2" 20.0"

**

17.7b

18.0"b

19.4" 0.79

Thighs

*** 27.2" 25.9b

26. lb

*

26.6" 26.5" 26. lb

0.35

1 Values are from 10 replicate pens of 50 birds/pen for each of two strains (Peterson x Arbor Acres and Ross x Ross) and rearing treatment. No significant strain differences occurred when statistical analysis included variance associated with separation of pen population by weight nor were there interactions among the main factors (P>.05). Data for the strains were combined, and the effects of rearing treatment and pen distribution presented as orthogonal comparisons. SEM has 2571 df.

2 M(41D) = males reared to 41 days of age; F(47D) = females reared to 47 days; C(44D) = combined sexes reared to 44 days.

"c Values, respective of part, not having a common letter are different (P < .05). *P<.05. **P<.01. ***P<.001.

310

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312

PERFORMANCE OF LAYING PULLETS FED DIFFERENT LEVELS OF COTTON SEED OIL AT VARIOUS AGES

A.A. El-Deek, M.A. Kosba, M. Farghaly and Y. Afifi

Department of Animal Production, Faculty of Agriculture, Alexandria University, Alexandria, Egypt

Abstract

A factorial experiment was designed, with three different ages of Alexandria laying pullets 26-38, 30-42 and 34-46 wks, and three dietary treatment included: 0, 2 and 4% of cotton seed oil at the expense of a basal diet. Thirty six laying pullets fed their diets ad libitum at each period of age. No significant differences due to oil levels or interaction was observed, but the effect of age was highly significant (P<0.01) on body gain. No adverse effect on egg production of added oil to the laying ration when the effect of age was overlooked. Feed consumed per bird decreased significantly with the increase of oil levels. The effect of age on feed consumption was highly significant. Feed efficiency was not significantly affected by adding different levels of oil, while it decreased as the age increased. Dietary oil level or age did not significantly affect blood, feather, carcass, liver, gizzard, abdominal fat, oviduct weight and length. No significant interaction between treatments and age was detected for carcass traits. The age of birds significantly affected the serum cholesterol level. Regardless of age, added oil to pullets diets increased serum cholesterol. Liver and abdominal fed cholesterol were also significantly increased by dietary supplements of cotton seed oil.

Introduction

Fat has been an important source of energy for poultry more than 25 years and the beneficial effect of supplemental fat on poultry performance have been documented. The use of fat and oil in laying hen rations has been relatively limited. Horani and Sell (1977) showed that supplemental fat increased the metabolizable energy values of laying hen diets more than would be expected from the dietary constituents. Likewise, Horani (1977) indicated that added fat increased net energy of laying hen rations primarily by increasing caloric gain in body tissue.

313

Factors such as breed, fatty acids included in the fat, minerals and age of bird could influence chickens' utilization of dietary fat. Variation in fat utilization with age was observed by Whitehead and Fisher (1975). The age or stage of egg production for hens fed oil supplemented diet was important. No previous studies have evaluated the effects of dietary oil supplementation initiated at different ages of production. This study was conducted to obtain information concerning the influence of feeding cotton seed oil on the performance of laying hens fed corn-soybean diet at various ages.

Materials and Methods

Five hundred Alexandria chicks were reared from one day to 16 weeks of age in floor pens. At 16 weeks of age two hundred birds were transferred to individual cages. At 26, 30 and 36 weeks 36 birds were randomized into three dietary groups with 12 birds each and then they were divided into 3 replicates with 4 birds each. Diet groups contained 0, 2 and 4% cotton seed oil added to the basal diet. The composition of diets are shown in Table 1. Each experiment period continued for 12 weeks. The following data were collected: body weight at the beginning of feeding oil and at monthly intervals, average body weight gain, feed consumption, feed efficiency, which was calculated as feed consumption per dozen eggs, mortality rate and egg number. At the end of the experiment period, nine birds from each treatment within each age were randomly chosen. Birds were individually weighed, slaughtered to complete bleeding and blood was collected in a dry clean tube. Giblets (heart, gizzard and liver) were weighed. Dressing percentage was calculated. Abdominal fat was collected and weighed. Oviduct length was measured. Shanks were cut out at the hick joint and weighed. Samples of flesh of breast and thigh were mixed and taken for analysis. Liver was weighed and subjected to the following analysis: moisture, ether extract, ash and crude protein. All analyses were carried out according to the official methods (AOAC, 1975). Total serum cholesterol was estimated according to the methods of Watson (1960). Total liver and abdominal fat cholesterol was estimated according to the method of Zlatkis et al. (1953). A factorial experiment was designed with three different age groups and three dietary treatments (Steel and Torrie, 1960). Duncan's multiple range test (1955) was performed to compare means of the different groups.

Results and Discussion

Body Weight Gain: No significant differences due to oil levels were observed. Age differences were highly significant (P<0.01). No significant interaction was observed between treatments and age groups for body weight gain. These results were in agreement with the findings of Voreck and Kirclgessner (1981), who found that body weight of

314

laying hens increased with increasing the level of fat or oil. On the other hand, March and Biely (1963) found that body weight was not significantly influenced by the level of fat in the rations of laying hens. Egg Production: The effect of age on the average of egg production (number of eggs/hen/month) was significant (Table 2). No significant differences were observed between the first age group and the second. However, the differences were significant (P<0.01) between the third group and the first and second group. These results are in agreement with the results of Horani and Sell (1977), who found that added fat had no significant effect on egg production. Furthermore, the results of Dammart and Giesslar (1982) are in agreement with the findings of this study. They found that number of eggs was affected by energy content of diet fed to Hisex or Alexandria hens. In contrast, Reddy et al. (1980) reported that increasing ME of diet fed to Hyline pullets significantly decreased egg production. Feed Consumption: Amount of feed consumed per bird decreased significantly with increasing oil levels from 0 to 4% (Table 2). The effect of age on feed consumption was highly significant regardless to the effect of oil level in diet. The decrease in feed consumption might be related to the decrease in rate of egg produced during the three age periods. These results are in agreement with results of Cunningham and Morrison (1977), who reported that addition of soybean oil, corn oil or tallow to diets of laying hens significantly decreased feed intake with increasing fat percentage in diet. Similar results were reported by Reddy et al. (1980) and Vogt (1983), who found that increasing the dietary energy resulted in a significant decrease in feed intake. It is well documented that poultry consume energy in amounts to meet their needs. Feed Efficiency: The efficiency of feed utilization (Kg diet/dozen eggs) was not significantly influenced by adding different levels of oil (Table 2). It is worth to note that feed efficiency decreased as age increased. These findings agree with the results obtained by Sell et al. (1976) and Abdel-Ghani (1986). It is evident from the results of this study that beneficial effects of fat on laying hen performance are closely associated with voluntary feed consumption and energy utilization. Such improvement in energy utilization upon fat supplementation may be attributed to the increase of the caloric density of the diet or an associated dynamic effect resulted from a lower heat increment and an extra metabolic effect caused by increased absorption and/or increased efficiency of dietary energy utilization. The results of Musharef and Vargas (1984) indicated that fat supplementation in layer diets could result in more caloric consumption. This energy could be utilized to increase rate of egg produced and consequently saving in feeding. Slaughter Traits: Regardless of age, dietary oil did not significantly affect weights of blood, feather, carcass, liver, heart, gizzard and abdominal fat (Table 3). No significant interaction between oil treatment and age was observed for the carcass traits. Abdel-Ghani (1986) found that increasing dietary oil level did not significantly affect dressed weight. It is clear from the present findings that increasing oil level to 2% or 4% resulted in an increase in abdominal fat by about 30% more than the control regardless the age.

315

Dry matter content of carcass was slightly increased with increasing the level of oil. The present results are in agreement with the results of Soliman (1983) and Abdel-Ghani (1986), who reported that moisture content of breast, thigh or liver in turkeys slightly decreased with increasing the level of dietary oil or fat. Further, the results indicated that protein percentage in thigh meat and liver gradually decreased with increasing oil level. However, protein percentage in breast meat increased with increasing the level of oil. These results are in agreement with the findings of Abdel-Ghani (1986), who found that protein percentage in liver decrease as a result of increasing the level of cotton seed oil in diet. Fat content of carcass tissues (breast, thigh and liver) increased with increasing the oil level from 0 to 2% and slightly increased by increasing the level of oil up to 4%. These results are in agreement with the results of Summers et al. (1965), who found that percentage of dry matter decreased and percentage of fat increased in the liver with increasing the level of dietary energy or the level of supplemental dietary fat. The different effects of dietary oil on the lipid accumulation observed in this study may be attributed to the fatty acids of the oil. The results are in agreement with the results of Bragg, et al. (1973) and Abdel-Ghani (1986) regarding fat accumulation in the liver of growing and laying hens fed saturated dietary fat or essential fatty acids. Average ash content of liver was significantly affected by feeding different diets. There was no significant interaction between diet and age for their effects on ash content. However, the interaction was significant in the case of protein and fat contents of breast, thigh and liver. No significant changes were observed in the chemical compositions of breast, thigh and liver during the periods of 30-42 and 43-46 weeks. Cholesterol Determination: Diet containing 4% oil resulted in an increase in the amount of serum cholesterol compared to the other two dietary treatments (Table 3), but the differences were not significant. Age significantly affected the cholesterol level in serum. These findings are in partial agreement with the results of Conner et al. (1969) and Abdel-Ghani (1986), who found that diets contained various levels of cotton seed oil or soybean oil tended to depress blood serum cholesterol. Liver and abdominal fat cholesterol levels were also significantly influenced by supplementing diets with cotton seed oil. Adding 2% or 4% cotton seed oil increased liver and abdominal fat cholesterol. Mickelbery et al. (1966) found that the highest quantity of cholesterol in liver lipids of broilers, while the abdominal fat had the least quantity. Miller and Denton (1962) found that dietary fat or oil did not significantly affect liver cholesterol content. It may be concluded that supplementing diets of layers with oil could result in more caloric consumption. This energy could be utilized to produce better performance with saving in feeding costs. Furthermore, the beneficial effect of the added oil was apparent at all age groups studied. However, evaluation of the effect the extra energy and the economic cost of adding oil to diets of laying hens needs further examination.

316

References

Abdel-Ghani, J. 1986. Studies on meat production in poultry. Ph.D. thesis. Cairo University, Cairo, Egypt.

Asar, M.A.; El-Deek,A., Hamdy, S. and Kosba, M.A. 1982. Effect of corn replacement by animal fat on the performance of different genetic back ground chicks. Egypt. Poultry Sei. 2, 85-96.

A.O.A.C. 1975. Association of official Agriculture Chemists. Official Methods of Analysis. 12th Ed.

Bragg, D.B.; Sim,J.S. and Hodgson, G.C. 1973. Influence of dietary energy source on performance and fatty liver syndrome in White Leghorn laying hens. Poultry Sei. 52, 736-740.

Conner, W.F.; Vitaik,W.E.,Stone, D.B. and Armstrong, MX. 1969. Cholesterol balance and fecal neutral steroid and bile acid excretion in normal men fed dietary fats with different fatty acid composition. J.Clin. Invest. 48, 1373-1375.

Cunningham, D.C. and Morrison, W.D. 1977. Dietary energy and fat content as factors in the nutrition of developing egg strain pullets and young hens. 3- Effects on hepatic lipogenic, enzyme activity and body chemical composition during the first 20 weeks of lay. Poult. Sei. 56, 1782-1791.

Dämmert, S. and H. Giessler. 1982. Egg yield and feed intake of laying hens given all-mash feeds with different contents of energy and protein. Archiv, fur Geflugelkunde 46, 84-94.

Duncan, D.B. 1955. Multiple range and multiple F tests. Biom. 11, 1-42. Horani, F.G. 1977. Effect of feed grade fat on efficiency of energy utilization by laying

hens. Unpublished Ph.D. thesis, North Dakota State University, Fargo, ND, U.S.A.

Horani, F.G. and Sell, J.L., 1977. The modifying effect of calorie: protein ratio on laying hen performance and on the "extrametabolic effect" of added fat. Poult. Sei. 56, 1981-1988.

Mickelbery, W.C., Rogier, J.C. and Stadelman, W.T., 1966. The influence of dietary fat and environmental temperature upon chick growth and carcass composition. Poult. Sei. 45, 313-321.

Miller, E.C. and Denton, C.A. 1962. Serum and egg yolk cholesterol of hens fed dried egg yolk. Poult. Sei. 41, 335-337.

Musharef, N.A. and Vargas, K.E. 1984. Supplemental fat in laying hens rations. NRA. B. No. 767. July-September 2, 3, 8.

Reddy, G.V., Reddy, C.V. and Reddy, V.R. 1980. Production traits of caged laying as influenced by their protein and energy levels. Indian J. Anim. Sei. 50, 748-752. (Cited by Nut. Abs. and Rev. 1981, 51, 876).

Sell, J.L., Horani, F.G. and Johanson, R.L. 1976. The extra-caloric effect of fat in laying hen rations. Feedstuffs, 48, 28-29.

317

Soliman, A.Z.M. 1983. Nutritional studies on turkey. M.Sc. thesis. Cairo University, Faculty of Agriculture, Cairo, Egypt.

Steel, R.G.D. and Torrie, J.H. 1960. Principles and procedures of statistics. McGraw-Hill book company, New York, U.S.A.

Summer, J.D., Slinger, S.J. and Ashton, G.C. 1965. The effect of dietary energy and protein on carcass composition with a note on a method for estimating carcass composition. Poult. Sei. 44, 501-509.

Vereck, O. and Kirclogessner, M. 1981. Effect of different crude fiber contents with different planes of energy on feed intake, egg yield and body weight of laying hens. Archiv, fur Geflugelkunde, 45, 33-41, (Cited by Nutr. Abst. and Rev. 51, 876).

Vogt, H. 1983. Effect of decrease in contents of energy and protein in feeds for laying hens. Archiv, fur Geflugelkunde, 47, 41-49, (Cited by Nutr. Abst. and Rev. 53, 658).

Watson, D. 1960. A simple method for the determination of serum cholesterol. Clin. Chem. Acta, 5, 637.

Whitehead, G.C. and Fisher, C. 1975. The utilization of various fats by turkeys of different ages. Brit. Poult. Sei. 16, 481-485.

Zlatkis, A., Zak, B. and Boyle, A.J. 1953. A new method for the direct determination of serum cholesterol. J. I^ab. Clin. Med. 41, 486-487.

318

Table 1 The composition of the basal diet and chemical composition of the three experimental diets.

Ingredients %

Yellow Soybean meal Rice polishing Fish meal (62% protein) Limestone Bone meal Salt Vit. and mineral (premix)

62.00 16.00 5.00 8.00 7.00 1.50

+ 0.50 0.20

Total

Chemical Analysis

Protein (%) ME energy (Kcal/Kg) Energy/Protein ratio Ca (%) P (%)

17.93 2802.00

156.26 3.46 0.34

Chemical Composition %*

Composition (%)

Basal Diet (0% Oil)

Basal Diet (2% Oil)

Basal Diet (4% Oil)

Dry Matter Protein Fiber Ash Fat N.F.E. Calorie/Protein

88.70+0.14 17.93+0.29** 3.07+0.23 9.45+0.46 4.00+0.10

66.15+0.84 156.26

88.49+0.20 17.60+0.30 3.88+0.24

10.50+0.31 6.64+0.15

62.01+0.60 159.64

89.26+0.16 17.56+0.40 3.30+0.09

10.66+0.34 8.13+0.06

61.25+0.63 163.02

+ Premix: each 2 Kg contain Vit. A 0.96mIU, Vit. D3 0.16mIU, V. E 0.8 g,UK, 0.16g, Vit.B 0.08g, Vit.B2 0.32g, Vit. B6 0.12g and Vit.B12 0.89g, Pantothenic acid 0.80g, Nicotinic acid 1.6g, Folic acid 80mg, Biotin 4mg, Choline chloride 40g, Copper 0.8g, Iodine 0.08g, Iron 2.4g, Manganese 4.4g, Zinc 4.4g and Selenium 0.008g. * Chemical analysis was expressed on dry matter basis. ** Each estimate obtained from 3 samples.

319

Table 2 Effect of different dietary oil levels on the average change of body weight, egg production, feed consumption, feed efficiency and carcass traits (g/Kg) of laying hens at different ages.

Trait

Body Weight Gain (gm)

Treat­ment Oil % (T)

0 2 4 Av.

Egg Production 0 (number of eggs/hen/ month)

Feed Consumption (g/b/day)

Feed Efficiency (Kg/F/Dozen Eggs)

Blood

Feather

Carcass

2 4 Av.

0 2 4 Av.

0 2 4 Av.

0 2 4 Av.

0 2 4 Av.

0 2 4 Av.

Age (A) in weeks 26-38

369.1 455.0 470.8 431.7A

16.6a

16.2a

15.4a

16.1A

125.9 112.1 107.1 115.0A

2.7b

2.4b

3.2b

2.8B

35.3 41.4 34.3 37.0

53.6" 63.2 55.4 57.4

657.0 653.7 638.2 643.0

30-42

140.0 75.0

105.0 107.6B

13.6abc

14.3abc

1 4 9 a b

14.3A

107.0 93.8 89.7 96.9B

3.3b

2.5b

2.3b

2.7B

26.8 31.6 26.1 28.2

42.7 39.7 48.3 43.6

691.8 681.2 675.9 682.9

34-46

86.7 95.5

187.5 115.8B

9.5 10.1 4.6 8.2

103.0 82.3 76.5 89.5C

4.5b

3.2b

11.2a

6.3A

49.7 32.0 27.4 36.4

55.7 53.6 44.9 51.4

664.4 683.5 703.4 668.8

Av.

198.6 215.7 262.5 224.5

13.3 13.6 11.8 12.9

112.0 98.3 91.1

100.5

3.5 2.7 5.6 0.6

37.3 35.0 29.2 33.8

50.7 52.2 49.5 50.8

664.5 657.8 672.5 664.9

Statistical significance MSE

22.10

0.37

0.05

0.55

2.80

2.30

7.60

T

ns

ns

**

ns

ns

ns

ns

A

**

**

**

**

ns

ns

ns

of TxA

ns

**

ns

*

ns

ns

ns

320

Table 2, continued

Trait

Liver

Heart

Gizzard

Abdominal Fat

Oviduct

Oviduct Length (cm)

Treat­ment Oil % (T)

0 2 4 Av.

0 2 4 Av.

0 2 4 Av.

0 2 4 Av.

0 2 4 Av.

0 2 4 Av.

Age (A) 26-38

17.2 20.4 17.7 18.4B

4.2 3.7 2.5 3.5B

12.7 12.7 11.6 12.3B

54.1 56.5 70.2 60.3B

----

----

in weeks 30-42

14.0 17.1 16.9 16.0B

3.9 3.9 3.2 3.7B

13.9 17.5 14.9 15.4A

61.2 89.0 96.6 82.3 A

7.3 10.8 8.9 9.0

36.0 39.7 37.3 37.7

34-46

20.5 25.2 24.1 23.3 A

5.4 5.6 6.8 6.0A

15.2 16.3 16.4 16.0A

69.6 97.1 77.9 81.5A

8.4 11.9 12.6 11.0

36.2 35.6 34.8 35.6

Av.

17.2 20.9 19.6 19.2

4.5 4.4 4.2 4.4

14.0 15.5 14.3 14.6

61.7 80.9 81.6 74.7

7.9 11.4 10.7 10.0

36.1 37.7 36.1 36.6

Statistical significance of MSE T A TxA

0.90 ns ** ns

0.30 ns ** ns

0.50 ns ** ns

4.30 ns * ns

0.90 ns ns ns

1.60 ns ns ns

* P<0.05, ** P<0.01, ns Not significant. MSE Mean square error Means with different superscripts differ significantly (P<0.05).

321

Table 3 Effect of different dietary oil levels on the chemical composition of the liver, breast and thigh meat, liver and abdominal fat and cholesterol concentration in serum laying hens at different ages.

Trait

Treat­ment Oil Age (A) in weeks % (T) 26-38 30-42 34-46 Av.

Statistical significance of MSE T A TxA

Dry Matter

0 2 4 Av.

Breast 27.9 27.5 29.2 29.5 31.7 27.7 29.6 28.2

27.7 29.4 29.7 28.9 0.50 ns ns ns

Protein

0 2 4 Av.

25.0° 26.7b

29.7a

27.2

20.6a 22.8C

21.6" 24.2b

21.2e 25.5C

21.1 24.1 0.80

Fat

0 2 4 Av.

2.7d

4.8b

7.7a

5.1

3.4C

5.2b

3.2C

3.9

3.0C

5.0b

5.4a

4.5 0.50

Ash

0 2 4 Av.

0.5 0.6 0.7 0.6

0.9 1.1 1.1 1.0

0.7 0.8 0.9 0.8 0.10 ns ns ns

Dry Matter

0 2 4 Av.

Thighs 29.6 28.1 32.8 31.3 29.1 28.3 30.5 29.2

28.9b

32.0a

28.7b

29.9 0.50 ns

Protein

0 2 4 Av.

20.4a 19.0cd 19.7a

19.5bc 20. lab 19.8a

18.6d 18.8cd 18.7b

19.5 19.3 19.4 0.20 ns

322

Table 3, continued

Trait

Treat­ment Oil Age (A) in weeks % (T) 26-38 30-42 34-46 Av.

Statistical significance of MSE T A TxA

Fat

0 2 4 Av.

7.2C

9.4a

7.0C

7.9

6.3d

8.8" 6.7d

7.2

6.8 9.1 6.9 7.6 0.40

Ash

0 2 4 Av.

0.5 0.8 0.5 0.6

1.3 1.6 1.4 1.5

0.9b

1.2a

1.0b

1.0 0.10 ns

Dry Matter

0 2 4 Av.

Liver 32.6b 36.8ab 34.7b

42.4a 34.0b 38.2b

39.6ab 42.0a 40.8" 38.2 37.6 37.9 1.08 ns

Protein

0 2 4 Av.

16.4b 17.3" 16.7a

16.2b 16.2b 16.2b

16.2b 15.8b 15.9C

16.2b 15.8b 15.9C 0.15 ns

Fat

0 2 4 Av.

15.0*1 15.8e 15.4C

27.4" 20. lb 23.8a

20.3b 20.5b 20.4b

20.9 18.8 19.8 1.23

Ash

0 2 4 Av.

1.7 1.4 1.4 1.5

1.6 1.3 1.2 1.4

1.7 1.4 1.3 1.4 0.06 ns ns ns

Serum 0 (mg ch./100 2 serum) 4

Av.

Cholesterol 107.3e 154.2C

147.7C 138.6d

198.9b 154.7C

143.0B 149.2B

246.0a

196.8b

239.7ab

227.5A

165.7 158.7 183.1 169.4 6.30 ns

323

Table 3, continued

Trait

Liver (mg eh./g liver)

Abdominal fat mg ch./g abdominal fat

Treat­ment Oil % (T)

0 2 4 Av.

0 2 4 Av.

Age (A) 26-38

----

----

in weeks 30-42

5.9d

7.4d

8.5b

7.3

14.6e

16.8bc

17.4b0

16.2

34-46

9.4ab

9.1ab

9.8a

9.4

15.9bc

19.3b

24.3a

19.9

Av.

7.6e

8.2b

9.2a

8.3

15.3e

18.3b

20.9a

18.1

Statistical significance of MSE

0.20

0.60

T A TxA

j(Of£ 3f£)(e sjesje

#* ** *

* P<0.05, ** P<0.01, ns Not significant. MSE Mean square error Means with different superscripts differ significantly (P<0.05).

324

IMPROVEMENT OF THE QUALITY OF DUCK MEAT

H. Pingel, R. Klemm and U. Knust

Karl-Marx-Universität Leipzig, WB Geflügel- und Kleintierzucht, Stephanstraße 12, 0-7010 Leipzig, F.R.G.

Abstract

The popularity of waterfowl is based on the excellent taste of its meat. The increased waterfowl meat production deserves more attention to quality of carcass and meat. Waterfowl has to be produced and processes in such a way that its meat appears on the market as an attractive food of high nutritive and sensoric value. Selection for high muscle proportion and low feed conversion ratio improves nutritive value. High temperature before slaughtering reduces tenderness and juiciness of breast meat.

Introduction

Ducks are widely used as a source of meat, eggs and feathers. Efforts in all fields have improved the fattening performance and reproduction rate of ducks. The high genetical potency of growth is a supposition for an efficient meat production with ducks. At the slaughtering age of 7-8 weeks for Pekin and 10 to 11 weeks for Muscovies 70-80 percent of the adult weight are reached. That means a high utilization of the growth capacity. The popularity of ducks is based on the excellent taste of its meat and special products, as smoked breasts or liver pie. The increasing duck meat production deserves more attention to quality of carcass and meat. The nutritive value of duck meat will be improved by increasing of muscle proportion and decreasing of fat content.

There are several possible ways of influencing the muscle proportion of ducks. One possibility is the crossing of commercial breeds with breeds that can fly and have a high percentage of breast muscle. Crossing of Muscovy ducks with Pekin ducks produces Mulards with high breast meat yield. They play a considerable roll because of their body conformation and have a reduced sex dimorphism compared to Muscovy ducks (Table 1). More attention should be paid to use the mulards to combine a high proportion of muscle of the Muscovies with the a reproductive rate of the Pekins.

325

Breeding for higher breast meat yield can be based on estimated breast muscles in live birds or on direct measurements in their relatives, for instance from dressing and dissecting progeny groups. Visual inspection and handling of live waterfowl is ineffective as an indicator of carcass composition, especially of breast muscle percentage, because of dense feathering on a cylindrical body. Therefore a probe was used to estimate breast layer thickness. A positive correlation was found between this measurement and breast muscle percentage of carcasses in ducks of about r = 0.7. Kain (1989) found that selection for proportion of breast and leg muscle based on progeny test information improves especially the breast muscle proportion and reduces the fat content of the carcass (Table 2).

The fat content of carcass can be reduced markedly by selection for low feed conversion ratio (feed consumption divided by body weight gain). A divergent selection for low and high feed conversion based on feed consumption and body weight gain of individuals from 4 to 7 weeks of age has resulted in a high differentiation in feed conversion (Table 3). Since large amounts of fat are deposited in subcutaneous tissue, the carcass of the line with low feed conversion showed a lower fat content and by reduced grill losses of legs.

The use of duck meat for further processing will be increased in the next years. For that reason attention has to be paid to the technological and sensoric properties of this meat. Some of these properties can be influenced by the course of glycolysis, setting on immediately after slaughter. External factors like starvation, stunning, scalding etc. can influence some meat characteristics. Very high temperatures before slaughtering of pigs can result in a high incidence of PSE meat (Briskey et.al., 1966). Wood and Richards (1975) have found similar results in the breast meat of chickens.

Material and Methods

An experiment on the effect of heat stress just before slaughter was carried out with 30 Pekins, 30 Muscovy ducks and 30 Mulards. They were slaughtered at 3 different ages (8, 11, 14 weeks), half of each group was exposed to heat stress (40-44°C) for two hours. The meat properties were investigated after thawing of the frozen carcass.

Results and Discussion

The results of the experiment are tabulated in Table 4 and 5. In contrast to the results of Birla (1980) the pH-values of breast and thigh meat are higher in the stressed groups (with exception of Muscovy ducks and Mulards at the age of 8 weeks). The analysis of variances (Table 6) showes significant influences of treatment and

326

genotypes with significant interactions between age and treatment for breast meat. There are highly significant influences of all three factors with significant interactions between age and genotypes and between treatment and genotypes in thigh meat. The meat colour of stressed birds is often darker than that of the control. This results indicate the tendency to DFD meat. Table 6 shows that the grill loss of thigh is highly significant influenced by treatment and genotype. There are also significant interactions between age and treatment and between age and genotype. The test panel noticed differences between samples. Especially tenderness and juiciness have been influenced negatively by heat stress (statistic significant treatment influence), particularly in the 14th week.

Also Tawfik et al. (1990) found a better juiciness in the control group (normal temperatures) in contrast to the birds grown under high temperatures.

The shear values are mostly but not significantly higher in the breast meat of stressed birds. The analysis of variance for the traits tenderness and juiciness showes a significant influence of age and treatment and significant interactions between age and treatment. Starvation at high temperatures for several hours cause stress in the birds. The level of plasmacorticosteroids increases and stimulates or blocks the enzyme chains in favour of an increased glycogenogenesis. (Sottair and Janksch, 1977; Schiilke and Hoch, 1970). An abnormal reduction of ATP and glycogen takes place in animals whose meat after slaughter has characteristics of DFD-meat. This reduction of ATP and glycogen has already been terminated at the moment of slaughtering (Potthast and Hamm, 1976, in Hamm, 1976). A big portion of lactate and glucose changed over from muscle into blood stream and the reserves of glycogen in the muscle are exhausted. When animals are slaughtered at that moment. The post-mortal glycolysis is very slow or does not take place. Because of the little substrate for reduction to lactic acid no hydrogen ions, which could reduce the pH-value rapidly are released. It could be an explanation for the variation of meat quality. The pH-values 15 minutes post mortem which are higher than 6.2 inform about slow or incomplete glycolysis in breast meat (Ristic, 1978).

References

Birla, Martina, 1980: Genetische Analyse der Fleischbeschaffenheit und Zusammenhänge zwischen Behandlung der Tiere vor dem Schlachten und der Schlachtkörperqualität bei Geflügel. Diss. A, KMU Leipzig

Briskey, E.J: et.al., 1966: Einflüsse ante-mortem auf die Fleischbeschaffenheit. Zeitschr. f. Tierz. u. Züchtungsbiologie, Nr. 82/3, 298-307

Hamm, R., 1976: Neue Erkenntnisse zur Biochemie des Fleisches: Veränderungen nach dem Schlachten. Fleischwirtsch. 1956/1, 79-84

327

Kain, H.H., 1989: Untersuchungen zur züchterischen Verbesserung des Fleischansatzes u. des Futteraufwands bei Pekingenten.Diss. A. KMU Leipzig

Klemm, R. and H. Pingel, 1988: Senkung des Futteraufwandes bei Pekingenten -Ergebnisse eines Selektionsexperiments über 8 Generationen. Tierz. 42, 432-433

Ristic, M., 1978: Einfluß der Transportbelastung auf die Fleischbeschaffenheit von Broilern. Fleischwirtsch. 58/6, 1031-1034

Schülke, B., Hoch, A., 1970: Zur Charakterisierung des Hungerzustandes. Arch. f. Tierern. 20,221

Sohair, Y.S., Jaksch, T., 1977: The effect of stress-factors on blood leucocytic count glucose and corticoids in chickens. ZBL. Vet. med. 24/2, 222-228

Tawfik, E.S. et.al., 1990: Einfluß der Stalltemperatur auf Mastleistung, Schlachtkörperwert und Fleischbeschaffenheit von Broilern unterschiedlichen Alters und Geschlecht. 4. Mitteilung: Sensor. Bewertung der Fleischbeschaffenheit. Arch. f. Gefl.-kunde 54/1, 14-19.

Wood, D.E. and Richards, J.F., 1975: Effect of some ante-mortem stressors of post­mortem aspects of chicken broiler pectoralis muscle. Poult.Sci. 54/2, 528-531

328

Table 1 Meat proportion of ducks.

Slaughter age, wks. Body weight, g. Percentage of carcass muscle breast muscle bones skin and fat

Muscovies M

11 3126

59.3 16.0 20.5 20.2

F

9 1932

55.6 14.6 21.0 23.4

Pekins M

8 2707

45.0 11.6 18.9 36.1

F

8 2610

45.2 12.9 19.3 35.4

Mulards M

9 3234

55.3 16.3 21.2 23.6

F

9 2993

54.6 15.3 19.4 26.0

Table 2 Effect of selection for muscle proportion on fat content of Pekin ducks (Kain, 1989).

Year n Proportion of carcass Breast muscle Leg muscle Crude fat

+ bones content

Ï979 ÏÏ55 Ï2Â Ï 5 J 29J 1985 240 15.6 16.1 26.9

Table 3 Effect of divergent selection for feed conversion on carcass composition in Pekin ducks after 8 generations.

n Feed Conv. 4th to 7th week Carcass comp. n Breast and Leg muscle, % Breast and Leg skin, % Crude fat content, % Grill losses of Leg, %

Low Feed Conv.

113 3.133

50 27.0 11.5 21.7 41.5

High Feed Conv.

149 4.349

39 26.0 15.0 30.1 50.8

329

Table 4 Meat quality characteristics of ducks exposured to acute heat and their control after thawing.

Age Genotype (weeks)

8 Pekings

Muscovy ducks Mulards

11 Pekings

Muscovy ducks Mulards

14 Pekings

Muscovy ducks Mulards

Treatment

Control Stress Control Stress Control Stress

Control Stress Control Stress Control Stress

Control Stress Control Stress Control Stress

pH breast

5.58 5.83 5.70 5.34 5.65 5.56

5.47 5.62 5.45 5.52 5.54 5.76

5.73 5.80 5.33 5.61 5.30 5.84

pH thigh

6.16 6.36 5.91 5.70 5.96 6.19

5.88 6.20 5.97 6.09 5.32 6.49

5.98 6.32 6.28 6.25 6.43 6.66

Remis­sion % breast

10.40 7.80

13.40 10.20 11.50 9.90

9.20 8.30 7.00 7.10 6.90 7.50

8.20 12.80 8.70

10.00 5.20

10.40

Grill loss % thigh

27.45 27.15 27.73 28.95 25.90 26.08

31.16 29.13 29.61 25.84 32.23 22.05

31.39 24.77 27.92 24.08 25.33 20.77

Juice loss % thigh

22.87 21.22 25.93 23.78 23.93 24.63

18.77 23.99 18.12 26.81 27.93 24.62

19.84 25.07 18.72 17.23 20.02 24.40

330

Table 5 Sensoric characteristics of grilled breast meat.

8 Pekings

Muscovy ducks Mulards

11 Pekings

Muscovy ducks Mulards

14 Pekings

Muscovy

Mulards

Control Stress Control Stress Control Stress

Control Stress Control Stress Control Stress

Control Stress Control Stress Control Stress

Tender­ness

2.5 2.5 2.8 2.4 2.3 2.6

2.3 3.3 2.6 2.6 2.5 2.9

2.8 3.4 3.0 3.6 2.7 3.30

Juici­ness

2.7 2.9 2.9 2.4 2.4 2.7

2.5 3.1 2.8 2.7 2.6 3.0

2.7 3.6 2.8 3.4 3.0 3.1

Flavour

2.5 2.3 2.5 2.3 2.3 2.4

2.2 2.8 2.4 2.4 2.3 2.5

2.5 2.8 2.6 2.9 2.6 2.6

Shear value N

77 85 95 79 73 88

98 96 91 85 66 89

103 98 90

126 99

110

The following notes were interpreted for the sensoric traits as to 1 = excellent; 5 = bad.

331

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332

AGE AND SEX INFLUENCES ON SLAUGHTER AND MEAT YIELDS IN PHEASANTS

F.H. Ricard, G. Marché and M.J. Petitjean

Institut National de la Recherche Agronomique, Nouzilly, F-37380 Monnaie, France

Abstract

Male and female pheasants could be reared in confined broiler-type poultry house without any specific problem. They were slaughtered when 10-, 14-, 17-, or 22-week old. Abdominal fat, eviscerated and meat yields were studied, showing everytime very high breast meat percentages and a dramatic increase of abdominal fat deposits with age. A 4 months rearing period produced a sufficiently lean bird weighing a little less than 1.5 kg for males and 1 kg for females.

Introduction

In France, ring-necked pheasants are commonly used for hunting purposes. Previous studies (e.g. Ricard and Petitjean, 1989) showed interesting carcass characteristics when released for shooting, namely low fat deposits and high breast meat yields. A more extensive experiment was carried out in our Institute to study effects of sex, age, and rearing (aviary vs. confinement) techniques. Results dealing with body weight, food conversion and fatness were recently published (Ricard et al., 1991). In the present paper, anatomical carcass composition is given for confinement-reared males and females slaughtered at 10-, 14-, 17-, and 22-weeks old.

Experimental procedures

A batch of 720 day-old pheasants were obtained from an I.N.R.A. strain bred at the Magneraud experimental Center (Petitjean et al., 1986). Birds, hatched in June 1989, were reared in two conventional confined broiler-chicken houses. Stocking density at day-old was 5 birds (sexes mixed) per square meter. Due to mortality (low after 6 weeks of age) and samples taken for slaughter, density dropped to 1.4 pheasants per square meter at 22 weeks of age. The same feed formulae containing 12.2 mJ of metabolizable energy per kg

333

and 288 g/kg of crude protein from hatch to 3 weeks of age, 240 g/kg from 3 to 6 weeks, and 214 g/kg thereafter.

A sample of 20 males and 20 females, representing the live weight distribution of the flock, was selected at each of 10, 14, 17, and 22 weeks of age. Bird dissections were performed according to W.P.S.A. Working Group 5 recommendations (1984). The following live body weight percentages were then obtained : abdominal fat deposits, edible giblets (gizzard + liver + heart), neck, fully eviscerated carcass, thighs, drumsticks, wings, and breast meat (all pectoral muscles). Classical analyses of variance were performed and mean comparisons obtained, using Newmann and Keuls test.

Results and Discussion

Mean values of live body weights and carcass parts percentages are given in Table 1 for each sex age (20 birds per group).

Live body weight is only 50 percent higher for 22- than for 10-week-old birds, showing a diminishing growth increasing rate after 10 weeks of age. The most important age effect is obtained with abdominal fat percentages : more than 3 times as high for 14- compared to 10-week-old birds, about twice as high for 17- compared to 14-week-old ones, again more than twice as high for 22- than for 17-week-old ones. Those results question the usefulness of rearing pheasants older than, say, 18 weeks for producing a sufficiently lean carcass.

When expressed in body weight percentages, edible giblets as well as legs and wings tend to decrease with increasing age. On the contrary, eviscerated carcass as well as thighs and breast meat increase. Carcass quality, expressed as high valuable part yields increases with increasing age. Results show no significant difference between 17 and 22 weeks for thighs, drumsticks and pectoral muscles percentages. Rearing pheasants older than 17 weeks will not improve thigh nor breast meat contents, the most valuable carcass parts. It is also interesting to point out that pectoral muscles represent a very important part of pheasant body weight (20 to 24%), higher than in guinea fowl (17 to 20%, see Ricard et al., 1986) and much higher than in broiler chicken (12 to 13%, see Ricard and Petitjean, 1989). This result may be of interest for cutting up pheasant carcasses.

Significant differences between males and females are summarized in Table 2.

334

Mean body weight is always higher in males than in females, the contrary of guinea fowl situation. The female/male ratio decreases from .77 to .71 between 10 and 17 weeks, comparable with chickens of similar ages. When expressed in body weight percentages, neck, drumsticks, and wings appear to be higher in males, while abdominal fat deposits are about twice times higher in females. Average values of eviscerated carcass percentages are about the same in both sexes. Breast meat is higher in females from 10 to 17 weeks of age, this difference is only significant for 10-week-old birds.

In conclusion, the present experiment showed that rearing pheasants in a confined environment is possible, without any specific problem, for producing a broiler-type bird. A four months rearing period will produce males weighing about 1.5 kg and females weighing a little less than 1 kg, with lean carcasses and high breast meat yields.

References

Petitjean, M.J., Guillot, P. and Malineau, G. 1986. Maitrise de la reproduction du faisan. Proceedings 7th European Poultry Conference, Paris, august 1986, Larbier M. ed., vol.1, 148-152

Ricard, F.H., Giffard, T. and Marché, G. 1986. Evolution en fonction de l'âge des éléments de la carcasse du pintadeau moderne. Proceedings 7th European Poultry conference, Paris, august 1986, Larbier M. ed., Vol.2, 874-877.

Ricard, F.H. and Petitjean, M.J. 1989. Composition anatomique de la carcasse du faisan de tir. Comparaison avec des poulets de poids similaire. Annales de Zootechnie, 38, 11-18.

Ricard, F.H., Petitjean, M.J., Melin, J.M., Marché, G. and Malineau, G. 1991. Croissance et engraissement de faisandeaux élevés en volières ou en claustration. I.N.R.A. Productions animales, 4, sous presse.

W.P.S.A., Working Group 5., 1984. Method of dissection of broiler carcass and description of parts, 33 pp., Jensen, J.Fris ed., Pergamon Press, Cambridge (GBR).

335

Table 1 Age effect on carcass composition in broiler pheasants (20 birds per group, carcass parts in % live body weight).

Slaughter age

1/ Males

Live body weight (g)

% abdominal fat % edible giblets (2) % neck % evisc. carcass % thighs % drumsticks % wings % pectoral muscles

2/ Females

Live body weight (g)

% abdominal fat % edible giblets (2) % neck % evisc. carcass % thighs % drumsticks % wings % pectoral muscles

10 wks

944 d

.08 c 4.00 a 3.31 abc 64.49 d 12.51 c 9.60 a 8.24 a

20.27 c

729 d

.18 d 4.29 a 3.06 a

64.42 c 12.17 d 9.33 a 7.79 a

21.15 c

14 wks

1245 c

.32 be 3.45 b 3.17 be

67.29 c 12.94 b 9.59 a 7.54 b

22.42 b

910 c

.61 c 3.53 b 2.70 b

67.24 b 12.66 c 9.17 a 7.34 b

22.65 b

17 wks

1359 b

.62 b 3.07 c 3.13 c

68.50 b 13.73 a 8.97 b 7.04 d

23.79 a

966 b

.99 b 3.30 c 2.73 b

67.89 b 13.20 b 8.44 b 6.94 c

24.39 a

22 wks

1445 a

1.22 a 2.78 d 3.39 a

70.62 a 13.76 a 8.90 b 7.32 c

24.45 a

1097 a

2.26 a 2.94 d 2.80 b

71.02 a 14.31 a 8.38 b 6.95 c

24.01 a

ig.sd (1)

93.25

.44

.25

.24 1.09 .62 .44 .28

1.10

70.14

.54

.28

.21 1.38 .74 .46 .27

1.25

(1) intra-group standard deviation (2) edible giblets = gizzard + liver + heart a,b,c,d = two means followed by the same subscript are not different (P>.05). Letter a shows the higher age value.

336

Table 2 Significant differences between sex means.

Slaughter age

Live body weight

% abdominal fat % edible giblets % neck % evisc. carcass % thighs % drumsticks % wings % pectoral muscles

10 wks

m

f f m 0

0

m m f

14 wks

m

f 0

m o 0

m m 0

17 wks

m

f f m 0

m m o 0

22 wks

m

f 0

m 0

f m m 0

m = male mean higher (P<.05) f = female mean higher (P<.05) o = non significant difference between sex means (P> .05)

337

338

QUALITY OF POULTRY MEAT IN VARIOUS EUROPEAN COUNTRIES

M. Ristic

Federal Centre for Meat Research, 8650 Kulmbach, Fed. Rep. of Germany

Abstract

The presented investigation comprises the origin of broiler from several European countries using different conditions of production (n = 140). The age varies between 37 and 90 days. The following breeds were included: Lohmann (D) 37 days, Hybro (NL) 40 days, "Polio Arena" (I) 40 days, ''Mamsell's-Mini-Roaster" (D) 50 days, Tetra (H) 52 days, "Mamsell's-Roaster" (D) 70days and "Label Rouge" (F) 90days.

The slaughter weight varied between 1.1 and 2.8 kg. The highest proportion of breast, breast muscles as well as total meat showed the Tetra-Roaster. The physical properties of the breast muscles were only slightly different between the breeds. The samples from Italy, Germany and France showed the better sensory scores. The average fat content of the breast muscles was 0.26% ± 0.14% and the average protein content 24.0% ± 0.29%.

Introduction

The fattening period of broilers takes about 5-6 weeks. Within this time a liveweight of 1.4 to 1.8 kg is reached with a feed efficiency of approximately 1 : 1.7 to 1 : 1.9. For a prolonged period of fattening traditional hybrides as well as the so-called roasters are available, as well as different feeding systems (OSMAN et al., 1989a,b; 1990; RISTIC et al., 1990; SOLIMAN et al., 1990; TAWFIK et al., 1989a,b; 1990;: VOGT et al., 1989a,b).

This investigation deals with the comparison of meat quality of broilers from various European countries on different rearing conditions.

339

Material and Methods

For this investigation the following breeds from various countries were used: Lohmann (D) 37 days, Hybro (NL) 40 days, "Polo Arena" (I) 40 days, "Mamsell's-Mini-Roaster" (D) 50 days, Tetra (H) 52 days, "Mamsell-Roaster" (D) 70 days and "Label Rouge" (F) 90 days. The broilers were stored 1-2 days as fresh broiler and then frozen and stored at -30°C for about 8-10 weeks.

In order to obtain meat quality criteria the following parameter of the breast and leg muscles were investigated: physical characteristics (pH-value, color, drip loss, grilling loss, objective tenderness), sensory data (juiciness, tenderness, flavor, overall impression), chemical composition (water, ash, fat, protein, fatty acids of the abdominal fat) as well as quantitative data of the slaughter value.

The statistical evaluation was carried out by means of a one-factorial analysis of variance (ANOVA); the significance was examined by means of the F-test.

Results

The slaughter weight was between 1078 g in test group D and 2757 g in test group B (Tables 1 and 2). A slaughter weight of 1465 g was reached with a prolonged free range farming management as it is the case in France (test group G). The meat/fat ratio, respectively meat/bone ratio was in favor of the test groups B and G, resp. B and C. Small differences were found while judging the trading classes.

There were highly significant differences (Table 3) regarding the proportion of cuts of the carcasses. The highest breast muscle proportions were found in the origins B and C, and the highest leg muscle proportions had origins F, G and origins A and B. The proportion of the abdominal fat varied between 0.41% (origin B) and 1.82% (origin H).

The tissue proportions of the breast muscles showed at the meat, bone and skin significant influence according to the origins (Table 4). The origins B and C (Tetra-Roaster) as well as origin G revealed the highest meat proportion. The proportions of bone, fat and skin reached an average of 12.9% (+ 1.35), 3.9% (± 0.60) and 7.6% (+ 1.31).

After thawing there were no differences in the tested origins concerning the pH-value of the breast muscle (x = 5.69, s = 0.11) (Table 5). The origins A and E had the lowest values of conductivity (mS/cm). The intensity of the yellow color (+b) was higher in the origins D, F and G than in the other tested groups. The proportion of maize in the feed was presumably higher in these groups. The liquid area in cm2, as parameter of the

340

juice-holding-capacity showed the lowest values with origins D and G. The grill loss of the breast muscles of 14% was the lowest with the groups B resp. F; the total mean value was 15.3% (+ 2.74). The grill losses found were approximately 5% lower than those in other investigations. The measured values of objective tenderness, measured with the Warner-Bratzler-apparatus, were influenced by the origins. The older broilers reached lower values than the origins A, C, D, E and F.

Judging the sensory scores, highly significant differences were found (Table 6). The origins F, E and B resp. B and F were in favor while judging the tenderness and overall impression of breast muscles. The leg muscles showed better values with the origins D and B resp. B and C.

The chemical composition of the breast muscles is listed in Table 7. The water, fat and protein contents varied among the tested origins. In spite of these differences one can say that the content of water and protein of the broilers was constant (75.5% + 0.33 resp. 24.0% + 0.29). The fat proportion of the breast muscles was the lowest with the origins G and B after a feeding period of 90 resp. 70 days, the highest with the origins C and A. The proportion of oleic acid (C 18:1) was on the average at 40.4% (± 2.69) and of the linoleic acid (C 18:2) at 22.1% (± 5.16). There were large differences among the tested origins: concerning the oleic acid among origins B, A and E resp., and concerning linoleic acid between D and A. These differences are presumably caused by the different fattening age and feed composition.

References

Osman, A.M.A., E.S. Tawfik, F.W. Klein, W. Hebeler, 1989a. Einflu/3 der Stalltemperatur auf Mastleistung, Schlachtkörperwert und Fleischbeschaffenheit von Broilern unterschiedlichen Alters und Geschlechts. 1. Mitteilung: Mastleistung. Arch.Geflügelk. 53, 168-175.

Osman, A.M.A., E.S. Tawfik, M. Ristic, W. Hebeler, F.W. Klein, 1989b. Einflu/3 der Stalltemperatur auf Mastleistung, Schlachtkörperwert und Fleischbeschaffenheit von Broilern unterschiedlichen Alters und Geschlechts. 3. Mitteilung: Grobgewebliche Zusammensetzung von Brust und Schenkel. Arch.Geflügelk. 53, 244-250.

Osman, A.M.A., E.S. Tawfik, M. Ristic, W. Hebeler, F.W. Klein, 1990. Einfluß der Stalltemperatur auf Mastleistung, Schlachtkörperwert und Fleischbeschaffenheit von Broilern unterschiedlichen Alters und Geschlechts. 5. Mitteilung: Physikalische und chemische Bewertung der Fleischbeschaffenheit. Arch.Geflügelk. 54, 20-28.

341

Ristic, M., Elisabeth M. Maurus-Kukral, F.X. Roth und M. Kirchgeßner, 1990. Schlachtkörperwert und Fleischqualität männlicher Broiler bei verlängerter Mast. Arch.Geflügelk. 54, 133-142..

Soliman, M.A.S., E.S. Tawfik, W. Hebeler, F.W. Klein, A.G. Galal, 1990. Schlachtkörperwert von Broilern: Gibt es Unterschiede zwischen den Herkünften? DGS 42, 454-457.

Tawfik, E.S., Osman, A.M.A., Ristic, M., Hebeler, W., Klein, F.W., 1989a. Einfluß der Stalltemperatur auf Mastleistung, Schlachtkörperwert und Fleischbeschaffenheit von Broilern unterschiedlichen Alters und Geschlechts. 2. Mitteilung: Schlachtkörperwert. Arch.Geflügek., 53, 235-244.

Tawfik, E.S., G. Baron, G. Dörken und W. Hebeler, 1989b. Nutzung der Wachstumskapazität männlicher Broiler. DGS 41, 877-881.

Tawfik, E.S., Osman, A.M.A., Ristic, M., Hebeler, W., Klein, F.W., 1990. Einfluß der Stalltemperatur auf Mastleistung, Schlachtkörperwert und Fleischbeschaffenheit von Broilern unterschiedlichen Alters und Geschlechts. 4. Mitteilung: Sensorische Bewertung der Fleischbeschaffenheit. Arch.Geflügek., 54, 14-19.

Vogt, H. u. S. Harnisch, 1989a. Broilerlangmast - Einfluß steigender Proteingehalte im Mastfutter. DGS 41 9-11.

Vogt, H. u. N.A. Musharaf u. S. Harnisch, 1989b. Broilerlangmast - Einfluß steigender Energiegehalte im Mastfutter. DGS 41 882-884.

SPSS Statistical Algorithms, Chicago, 1986.

342

Table 1 Material of investigation.

Group

A B C D E F G

Origin

Germany Germany Germany Hungary The Netherl. Italy France

Brand

usual fattening " Mamsell's-Roaster" " Mamsell ' s-Mini-Roaster "Tetra" usual fattening "Polio-Arena" "Label Rouge"

Fattening period

37 days 70 days 50 days 52 days 40 days 40 days 90 days

Table 2 Carcass data.

Cause of variance

Origin Group A B C D E F G

(D) (D) (D) (H) (NL) d) (F)

Slaughter-weight

***

1207.2 2756.8 1412.5 1077.9 1095.0 1082.7 1465.0

Meat/Fat relation (Breast)

*

18.6 27.7 20.8 16.7 18.9 20.3 26.0

Meat/Bone

***

5.0 7.2 6.8 5.0 5.3 5.4 5.8

Trading class

*

1.0 1.0 1.0 1.4 1.1 1.0 1.0

343

Table 3 Proportion of cuts in the carcass - as percent of the slaughter weight.

Cause of variance

Origin Group A B C D E F G

(D) (D) (D) (H) (NL) (D (F)

Breast

***

27.7 31.7 30.1 28.1 29.4 28.8 27.0

Back

***

21.8 20.9 23.4 23.2 23.7 23.7 22.7

Wing

***

12.2 11.7 11.9 12.7 13.0 12.4 12.2

Leg

##*

33.1 33.1 31.2 32.3 31.2 33.6 33.3

Abdominal fat

***

1.64 0.41 1.22 1.82 1.78 0.74 1.33

Table 4 Tissue proportion of the breast - as percent of the breast muscle.

Cause of variance

Origin Group A B C D E F G

(D) (D) (D) (H) (NL) (I) (F)

Muscle

***

69.1 77.5 75.2 69.3 70.2 71.8 74.2

Bone

***

14.1 10.9 11.1 14.2 13.5 13.4 12.8

Fat

n.s.*)

4.0 3.4 4.2 4.8 3.9 3.8 2.9

Skin

##*

9.3 5.8 6.6 8.2 8.9 7.8 6.6

*) n.s. = not significant

344

Table 5 Physical criteria of the breast muscle.

Cause of variance

Origin Group A B C D E F G

(D) (D) (D) (H) (NL) d) (F)

pH-value

n.s.

5.75 5.69 5.64 5.68 5.69 5.71 5.69

Conductiv. value

***

10.1 11.4 11.5 11.6 10.1 11.1 11.1

+b

***

10.3 10.8 11.9 14.7 12.1 15.0 14.6

Juici­ness area/cm2

###

7.3 5.1 5.2 3.4 5.7 5.9 4.1

Grill-loss %

**

17.9 13.9 15.1 17.1 14.7 14.0 14.3

Warner-Bratzl.

***

3.3 1.4 2.0 2.0 2.9 3.0 1.6

*) n.s. = not significant

Table 6 Sensory data.

Cause of variance

Origin Group A B C D E F G

(D) (D) (D) (H) (NL)

(I) (F)

BREAST Tenderness

***

5.2 5.4 5.3 5.1 5.4 5.6 5.3

Overall impression

***

4.7 5.0 4.5 4.3 4.7 5.0 4.7

LEG Tenderness

**

5.2 5.3 5.1 5.5 4.9 5.0 5.1

Overall impression

*#*

4.5 4.8 4.8 4.3 4.4 4.2 4.5

345

Table 7 Chemical composition of the breast muscles as well as fatty acid of the abdominal fat - as percent of the fresh weight.

Cause of variance

Origin Group A (D) B (D) C (D) D (H) E (NL) F (I) G (F)

Water

***

75.4 75.1 75.1 75.9 75.4 75.9 75.4

*) n.s. = not significant Cl8-1 = Oleic acid

Ash

n.s.*)

1.19 1.21 1.16 1.18 1.22 1.23 1.19

Fat

***

0.41 0.13 0.48 0.18 0.22 0.28 0.12

Protein

**#

24.1 24.4 24.1 23.6 24.2 23.7 24.2

C18-1

***

37.5 37.3 39.8 42.6 44.7 41.3 39.5

CI 8-2

***

29.7 26.1 24.0 14.9 22.0 21.7 16.6

CI8-2 = Linoleic acid

346

INFLUENCE OF RAPESEED PRODUCTS ON BROILER PERFORMANCE AND MEAT QUALITY

E. Swierczewska, J. Niemiec and J. Mroczek

Warsaw Agricultural University, 05-840 Brwinów, ul. Przejazd 4, Poland

Abstract

Supplements of5.5% ground rapeseed or 7% extracted rapeseed meal to broiler feed have significant influence on meat colour. Hemin content in broiler muscles receiving that feed was twofold higher than hemin content of broilers fed a mixture without rape. The application of rape to broiler feed did not affect detrimentally active acidity water holding capacity and thermal drip of muscles.

Introduction

In countries with a great share of rape under cultivation as in Poland, many studies on the usefulness in poultry feeding of the double refined rape with a low glucosinolate and non eruc acid content are conducted. It is suggested that the supplement of rapeseed to poultry feed may be used not only in a form of extracted rapeseed meal but also as ground rapeseed (Króliczek et al., 1979; Lacassagne, 1981; Summers et al., 1982; Hanczakoswki and Fras, 1983; Mazanowska et al., 1987 and Wurzner et al., 1989). The supplement of rapeseed provides a great amount of energy, deficit component in those regions where no corn is cultivated. Moreover the rapeseed protein is a source of higher biological value than the protein enclosed in the extracted rapeseed (the extraction processes cause thermal damage of protein quality). There is a controversial opinion connected to the possibility of using rapeseed in feed mixtures. So, it gives the impulse to study the influence of extracted rapeseed meal and ground rapeseed on broiler production results and broiler meat quality.

347

Materials and Methods

Research was carried out on 1500 broiler chicks divided into 3 groups in 5 replications each. The chicks of group I (control) were fed a mixture with ground wheat, ground barley and ground soybean. Two other groups received feed with decreased amount of ground soybean. Group II received 7% of extracted rapeseed meal (from variety Star 00), and group III 5.5% of ground rapeseed of the same variety (Table 1). The broilers were weighed individually at 3 and 7 weeks of age. Feed intake and survival rate were observed. After slaughter, carcasses of 20 cocks and 20 hens from control and experimental groups were dissected and the following parameters were recorded: carcass yield, breast, thigh and drumstick muscle yield, heart, gizzard, liver and abdominal fat yield. Physical and chemical analysis of breast, thigh and drumstick muscles were conducted using the following methods: water content with the drying method, protein content with the Kjeldahl's method, fat content with the Soxhlet's method, pH using M-512 pehameter, hemin content with the Hornsey's method (Hornsey, 1956), water holding capacity (Wierbicki et al., 1962) and thermal drip with the method of Kotter et al. (1968). The results of the experiment were processed using statistical methods.

Results and Discussion

The chicks fed with a supplement of ground rapeseed had the higher body weight; this result is in agreement with the data of Lacassagne (1981). The lower body weight of broiler receiving the extracted rapeseed meal was probably caused by a lower nutritive protein value (result of extraction process). Feed consumption/kg of body weight in group III (with ground rapeseed supplement) was the lowest (Table 2). The slaughter analysis and dissection did not confirm the significant influence depending on kind of rapeseed product used. The basic analysis of chemical composition of breast and tibia muscles did not show differences depending on sex and diet either. The same was stated in connection to technological characters of muscles: the water holding capacity and the thermal drip. However, distinct differences between breast and tibia muscles colour was shown. The hemin concentration was twofold higher in muscles of broilers fed with ground rapeseed supplement. So, it seems that using rapeseed (with a low glucosinolate and non eruc acid content) improves meat colour without a negative effect on technological meat quality variables.

348

References

Hanczakowski, P. and Fras, B., 1983. Wartosc odzywcza nasion i Srut poekstrakcyjnych z rzepaku tradycyjnego i podwójnie ulepszonego. Rocz. Nauk Zoot. 10 (1), 91-96.

Króliczek, A., Kinal, S., Gwara, T. and Mazanowska, A., 1979. Zastosowannie preparowanych nasion rzepaku w zywieniu kurczat rzeznych. Rocz. Nauk Zoot. Monogr. i rozpr. 13, 25-36.

Lacassagne, L., 1981. Alimentation des volailes: substitutes an tourtean de Soja. INRA Prod. Anim. 1 (2), 123.

Mazanowska, A., Kinal, S. and Gwara, T., 1987. Zastosowanie poekstrakcyjnej Struty rzepaku odmian podwójnie ulepszonych (MAH+BOH) w zywieniu kurczat brojlerów. Rocz. Nauk Zoot. Monogr. i Rozpr. 25, 193-203.

Summers, I.D., Shen, H. and Leeson, S., 1982. The value of canola seeds in poultry diets. Can. J. of Anim. Sc. 62 (3), 861-868.

Wurzner, H., W. Wetscherek and F. Lettner, 1989. Rapsextraktionsschrot in der Huhnermast. Arch. Geflügel. 1 (6), 6-12.

349

Table 1 Percentage composition of feed.

Ground wheat Ground barley Ground soybean Extracted rapeseed meal Ground rapeseed Fish meal Bone meal Fodder yeast Dicalcium phosphate Fodder lime Lysine 20 premix Methionine premix Fodder salt Premix Pork fat

Protein % ME (MJ in 1 kg)

I

37.0 28.5 21.0

--6.0 6.0 3.0 0.4 0.2 0.3 0.3 0.3 1.0 1.0

21.2 12.0

Group II

37.0 27.0 16.5 7.0 -5.0 5.0 3.0 0.1 0.5 0.3 0.3 0.3 1.0 1.0

21.1 12.0

III

37.0 27.0 18.5

-5.5 6.0 6.0 2.5 0.1 0.5 0.3 0.3 0.3 1.0 -

21.0 12.0

350

Table 2 Performance of broiler chickens (body weight in g).

Sex

Males X

V

Females X

V

Age 3 weeks

I

532a

12

493a

10

Feed consumption per 1 of body weight (kg)

II

477b

15

433b

12

kg

Group III

540* 10

488" 12

Age 7 weeks

I

1796" 11

1513" 8

2.50

II

1624b

13

1341b

14

2.77

III

1859' 10

1534» 8

2.42

Mean values in rows with different letters are significantly different at P<0.01.

351

Table 3 Physical and chemical analysis of the breast and tibia muscles.

Group

I Feed without rapeseed products

II Feed with extra cted rape-

Ill Feed with ground rapeseed

Muscles

Breast

Tibia

Breast

Tibia

Breast

Tibia

Water %

74.6

74.7

74.5

74.6

74.5

74.6

Pro­tein %

23.4

19.7

23.3

19.6

23.3

19.6

Fat %

0.95

4.20

1.05

4.40

1.20

4.55

pH 48

5.7

6.4

5.8

6.5

5.7

6.9

Hemin content /xlO4

43.3

66.3

75.1

85.8

78.2

119.8

Water holding capaci­ty %

33.4

83.0

35.5

81.9

35.7

82.9

Ther­mal %

12.9

11.9

13.2

12.4

13.9

12.7

352

SESSION M5

AUTOMATION AND PROCESS CONTROL

353

AUTOMATION AND PROCESS CONTROL IN POULTRY PROCESSING PLANTS

C.H. Veerkamp

Spelderholt Centre for Poultry Research and Information Services, Agricultural Research Service (DLO), 7361 DA Beekbergen, The Netherlands

Abstract

Automation of slaughter poultry is increased by flexible rehanging systems, in-line chilling methods, cut-up lines and more use of electronic weighing systems. Electronic weighing systems are the most important for measuring yield and operation control. Overall process controlling procedures are not applied. Yield control on a flock basis is just started, using existing weighing systems and computers. Standard yield values for comparing actual yield data can be calculated. Rapid developments in controlling product flow and storage handling of the end products are expected. Plant and quality control managers in industry should take the advantages of these developments.

Introduction

The main developments in poultry processing over the last few years have been the increase in size of the birds and an increase in portioning of carcasses and further processing. The processor has become more aware of the quality of the product and of the need to control product and processing operations. In the mid-seventies the uses of digital concepts and hardware to manage and control food processing plants were discussed as means of satisfying industry's need for quantitive information on performance of plant and product. Many publications at that time dealt for example with the use of computers in the food manufacturing industry for quality assurance (Molnar, 1978), data acquisition and process control (Shah and Bizarro, 1975) or process optimalization and automation (Thieme, 1973). At that time, the poultry processing industry introduced the first electronic weighing systems combined with a computer and possessing the ability to sort and drop carcasses at the relevant packaging stations. Following this initial application, however, the increase in the use of computers in the poultry industry has not been as large as expected (Veerkamp et al., 1981; Moriarty, 1984a), although new applications for computers are still being developed (Babbit, 1988; Benoff, 1986; Dyer, 1987; Dyer, 1988).

355

The advantages of computers result mainly from the speed of collecting and processing data and presenting the resulting information at real-time, thus making very fast decisions possible for managers or operators. The information can also be used in a closed-loop, real-time process control, where the computer interacts with a process directly. The state of the art regarding process control, yield control, quality control and other computer applications currently employed in the poultry industry will be described in this paper, together with projected future developments.

Process Control

Process control consists of: - measuring devices as sensors, scales etc. - soft- and hardware to collect and process data - calculation models - standard values for comparing actual values - feed back procedures for adjusting equipment, mass flow, presenting printed

information etc.

Weigh cells are the most important measuring devices in poultry slaughtering and can be used in direct connection with the computer. They are presently mainly used for grading according to weight, to control product flow for the various packaging stations or making a selection for the cut-up line. Other measuring devices such as electronic counters, flow, mass and energy meters and temperature controllers can all be used for automatic data collection. A lot of data are still being collected manually in poultry slaughtering operations by keeping track of records. These are for example: - live weight, age and other information on the flock - weight and numbers of DOA's (dead on arrival), - weight and numbers of condemned carcasses and parts, - results of carcass quality inspection of the flock. Reporting condemnations by computer was tested in an USA plant using four data entry stations and two electronic bird counters (Moriarty, 1984b). Several changes would probably be necessary before the system could be produced commercially. No further developments have been described to date. It is impossible in most cases to relate available information on the in-coming flocks to information collected during processing. Even the quantity and quality of the final products produced from each flock are presently not known. Real-time control of all integrated operations of the plant is beyond the scope of today's poultry industry.

356

Yield Control

Yield in food processing is defined as: " the product out divided by the raw material in". Calculations of average yield are carried out at the end of each day in many plants. The results are used to adapt slaughtering and cutting operations. This information is always available too late to make corrections during handling or for changing production variables. Differences of less than 0.5% in daily yield data are very difficult to explain afterwards and not easy related to individual flocks or processing conditions. However, for an average processing plant (7000 carcasses/hour), a daily loss of 0.1% in yield implies a financial loss of about 40.000 ECU annually. The introduction of automatic control of yield seems to be justified because savings in yield can be expected and return on investment obtained by continuously monitoring the successive operation in the plant. In accordance with the definition of yield, in poultry processing, two equations are used:

Yield = (Wx / W,) * 100 %

or Yield = [1 - (Wx - Wx+1)/ W, ] * 100 % in which: W, = live weight just prior to slaughter, after a minimum fasting period of 4 - 5 hours Wx = input weight of operation x Yield values of a flock are dependent on several factors : - strain, age and weight - feed and housing conditions - processing conditions. Holsheimer and Veerkamp (1989) carried out research to study the effect of feeding conditions to increase breast meat yield. Standardized dissection procedures developed by Working Group no 5 of the European Federation of the WPSA (Fris Jensen, 1985) are always used for estimating yield values at the Spelderholt Centre. Fig. 1 shows the combined influence of weight and age on carcass yield of male broilers. The carcass yield (including neck skin and abdominal fat) for a mixed flock can be described by the following formula:

Yield = 65.95 - 0.161 * L + 5.905 * G

in which L = age in days G = weight in kg

From the equation it can be concluded, that fast growing broilers have the highest carcass yield. This conclusion is also valid for breast meat and legs, the most valuable parts of broilers. Regression equations for calculating yield values of most operations in broiler processing and of broiler parts are presented in Table 1.

357

A comparison of these equations with those from 1982 (Veerkamp, 1983) shows that today's broilers have higher yield of breast meat, liver and back and lower yield of legs and gizzard.

74

73

72

71

70

carcass (%)

<> ^ * ^

l ive weiqht (a) ^S^"i >

< 3 ' ^ ^ ^ ^*

3500

3200

2900

2600

2300

2000

age (weeks)

Figure 1 Mean carcass yield values in relation to age and live weight for male broilers of 2 commercial broiler strains.

In industrial slaughtering CARCASS PRODUCTION YIELD can be used as a parameter for quality of the delivered flock. This yield is:

Average carcass weight after chilling corrected for weight of condemned parts:

Wa = (Wp * N, + Wcp) / Nt

Average live weight: W, = Wt / N,

Carcass Production Yield = (Wa / W,) * 100 %

358

in which:

Wp = average carcass weight determined by electronic weighing Wcp = weight of condemned parts W, = total weight of delivered birds - weight of DOA's - live weight of whole

condemned birds Nt = total number of delivered birds - number of DOA's - number of whole

condemned birds = total counted on the slaughter line - number of whole condemned birds = total weighed on the electronic weighing equipment

The live weight of the condemned whole birds can be estimated as weight of condemned carcasses (including intestines and giblets) multiplied by a factor 1.2. The total delivered weight should be determined by weighing the live birds just prior to hanging on the line. Weighing of the birds just after loading or on arrival at the plant for the purpose of calculating this yield value will intermix the various losses during fasting and holding with the effects of processing conditions .

The best indication of broiler quality is obtained if carcass weight is determined in the absence of by-products such as abdominal fat, neck or neck skin. It seems to be logical to remove these parts before estimating the weight of the valuable parts of the carcasses. However, at this moment this is not common practice in most poultry processing plants. The actual carcass production yield values of flocks can be compared with theoretical values calculated using the equations of Table 1. The grower can then be paid more according to a real value of the broilers for processing than by live weight. An example of a sheet which can be used to report control parameters back to the producers is shown in Table 2.

In the example condemnations are not included in the payable weight. The number of birds counted on the slaughterline decreased by the number of whole condemned carcasses is the basis for calculating the payable carcass weight (= (25 561 - 104) * 1.209 -47 kg). The difference in number of carcasses between hanging and weighing is due to condemnation of whole carcasses and partly (= 21) to processing. The theoretical yield value is calculated with the equations of Table 1. subtracting the yield of neck skin from the carcass yield. The factor 1.2 to multiply the weight of the condemned carcasses is an average value used to calculate live bird weight from condemned carcass weight. The value of the efficiency can exceed 100 % because the standard yield value is not based on maximum yield values. On the other hand operations in practice use sometimes slightly different cutting techniques or the carcass have some water uptake during cleaning, both resulting in efficiencies > 100 %.

359

Quality Control of Visual Defects

Costs of downgrading are important in the quality of flocks arriving at the processing plant. Downgrading is the result of quality defects, which lead to condemnations of whole carcasses or parts or to restrictions in the processing possibilities of the product. An objective assessment of quality attributes of flocks (Daniels et al., 1989), may improve the conditions during the growing period and transportation to the processing plant, especially when these quality factors are related to future financial results for the grower. Visual defects are caused by: - mechanical damage, resulting in bruises with or without broken bones or breast blisters, - litter conditions, resulting in litter "burns" or litter "spots" on the breast, - management, resulting in scabby hips or a large variation in size of birds.

The grading should be done by a trained, quality inspector on the line, using references scales for the defects and data terminals to enter the scores. The results can be summarized and combined with the yield data report for the grower. It is expected that in the near future quality grading will be operated with video imaging techniques.

Automation and Product Flow Control

Product flow in processing carcasses is currently controlled by manual grading operations and by electronic weighing systems both linked to a computer. Automation of chilling system, packaging stations, rehanging equipment, flexible cut-up lines and storage makes it possible to control carcass flow completely. The FIPP (flexible integrated poultry processing) system of the Meyn company is one of the latest developments in this respect. It consists, for example, of 2 cut-up lines and 2 lines for cutting the saddles. The principle of this system can thus be described very easily: Special shackles with product are, dependent on weight and grade, removed from the overhead conveyor and via a buffer stock, inserted in one of the following overhead conveyors of the cut-up lines. After the initial cutting operation, the shackles with remaining saddles are combined in one line, weighed and assigned according to weight to the saddle cutting lines. Each shackle contains a microchip, which makes it possible to combine the in-line weighings in order to calculate the yield of the various cutting operati­ons. In this way a more accurate cutting and a higher overall yield are obtained. The system also offers the possibility of increasing the harmonization of production to consumer demand in respect of weight and variation in the way of cutting. At the moment the system is in operation in 2 processing plants in The Netherlands and Belgium. The

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system seems also to have promising prospects for chilling and aging carcasses before cutting and filleting. An automatic rehanging system with a built-in weighing station, produced by the Stork PMT, makes it possible to divide the carcasses according to weight over various cutting lines in order to optimize the cutting operations. Methods for product identification by bar code, chips or magnetic strip are used for crate/carton handling in the total logistic system of poultry processing operation. The principle of "first in, first out", the increase in the number of end products and the relative short storage life of fresh poultry products makes it mandatory that storage handling should be given attention by the processors. Uniform solutions are not available, but in many situations sophisticated techniques are used.

References

Babbit, S., 1988. Machine vision: Poultry quality control by computer. Poultry International 27, (7), 27-32.

Benoff, F.H., 1986. Predict carcass differences. Poultry 2, (5), 20-23. Benoff, F.H. and Wing,T., 1987. Broiler yield: I The importance of breed selection to

your bottom line. II The importance of accurately measuring yield. Ill Getting at the 'bottom line' with yield information. Published by Cobb Inc., Concord, Massachusetts, 01742, USA.

Benoff, F.H., 1987. Economics and measurement of broiler product yield. Broiler Industry 50, (9), 28-32.

Daniels, H.P., Fris, C , Veerkamp, C.H., Vries, A.W.de and Wijnker, P., 1989. St­andard methods classification broiler carcasses. Board of Poultry and Eggs, 3704 HA Zeist, The Netherlands.

Dyer, J.M., 1987. Critical points in monitoring yield. Poultry International 26, (7), 34-40.

Dyer, J., 1988. Today's information today. Broiler Industry 51, (9), 44-48. Hewell, J., 1987. Obtaining better yield. Poultry Processing 2, (1),36-39 Holsheimer, J.P. and Veerkamp, C.H., 1989. Meer filet en minder vet in slachtkuikens.

Pluimveehouderij 19, (10 maart), 6-7. Jensen, J. Fris, 1985. Method of dissection of broiler carcases and description of parts.

European Federation WPS A Working Group 5. Molnar, P., 1978. Anwendung der Prozeßoptimierung zur Qualitätssicherung und -

entwicklung in der Lebensmittelproduktion. Zeitschrift für Wissenschaft und Technik 25, 193-197.

Moriarty, L., 1984a. Computers seen having a new role in processing. Poultry & Egg Marketing, 64 (3), 10-15.

Moriarty, L., 1984b. Condemnation reporting by computer. Poultry Int. 23, (12),68-73.

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Shah, M. and Bizzarro, L., 1975. New computers measure up in food process control. Food Engineering 47, 59-62.

Thieme, W., 1973. Steuerung von Verfahrensabläufen der Lebensmitteltechnik mit Prozeßrechnern. Ernärhrungswirtschaft / Lebensmitteltechnik 10, 746-767.

Veerkamp, C.H., Mast,M.G. and Janssen, J.A.M., 1981. Process control for the poultry industry and for yield of the operations. 5th Symposium Quality of Poultry Meat, European Federation WPSA Working Group 5, Edit. Mulder, R.W.A.W., Scheele, C.W. and Veerkamp, C.H.; Spelderholt, Beekbergen, The Netherlands. 5-13.

Veerkamp, C.H., 1983. Estimating and using processing yield standards. 6th Symposium Quality of Poultry Meat, European Federation WPSA Working Group 5, Edit. Lahellec, C , Ricard, F.H. and Colin, P., 22440 Ploufragan, France, 329-340.

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Table 1 Constants to calculate yield percentage of live weight for a mixed flock with the linear regression equation : yield = a + b * age (days) + c * live weight (kg).

YIELD

slaughter

evisceration

carcass (incl. neck skin, fat)

heart

liver

gizzard

wings

breast meat

legs

abdominal fat + back skin

back

thighs

drumsticks

neck

neck skin

oven-ready incl. giblets

a

82.99

81.97

65.95

0.73

2.96

1.66

8.67

12.77

22.08

7.10

12.86

12.99

9.44

2.40

2.41

73.00

b

-0.0875

-0.0740

-0.1612

-0.0042

-0.0186

-

-

-0.0785

-

-0.0806

+0.0240

-0.0360

+0.0283

-

-0.0382

-0.1496

c

+2.494

+3.412

+5.905

+0.033

-0.070

-0.225

-0.230

+2.595

+0.956

+2.045

+0.177

+ 1.153

-0.199

-0.218

+0.381

+4.930

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Table 2 A sheet for reporting flock information to producers about yield.

general

name :

breed :

age (days):

smith

a

43

numbers

catched and loaded

dead on arrival

on slaughterline

whole condemned

chilled carcasses

25 640

75

25 561

104

25 436

weight

total delivered (kg)

tarra (kg)

total net weight (kg)

dead on arrival (kg)

whole condemned (kg * 1.2)

Condemned parts (kg)

56 980

11 483

45 497

127

175

47

live weight (g)

carcass weight measured (g)

carcass weight corrected (g)

1775

1207

1209

carcass production yield

actual (%)

Theoretical (%)

Efficiency (%)

68.1

68.06

102

total payable carcass weight (kg) 30 730

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A PROCESSORS VIEW ON AUTOMATION

J. Obdam

Plukon Poultry Industries, 8091 AZ Wezep, The Netherlands

Abstract

Automation in the poultry industry involves ergonomics, economics and product quality. Achievements in the modern poultry processing industry are analysed and scope for further developments is indicated.

Introduction

In the food processing industry, and specially in the meat industry, poultry processing is a young branche. When, some 40 years ago, poultry started its way to the top, other types of meat like beef, veal, pore and lamb were already well established. In poultry production all disciplines involved have made remarkable efforts and progress to support this development. Breeding, feed formulation, hatcheries, housing facilities, processing and distribution all have provided their part of the solid base for the success of poultry as a major food commodity. During the last four decades poultry processing has developed into a line-bound operation, where the manual work has been replaced -piece by piece- by machines and modules. The replacement of manual labour, for economic and/or ergonomie reasons, has been, for a long time, the main incentive for automation. Often also quality improvement could be achieved at the same time, but not always. Nowadays it is unthinkable to operate a processing plant without the basic automation in the slaughtering- and evisceration section. At several points however there is still a necessity for further development, especially from the quality point of view. In addition to this, the development in recent years of cut up-, deboned- and further processed products, has called for new automation; and this process is still far from complete, as we hope to illustrate in this contribution.

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Handling of live birds

The handling and transport of poultry from the farm into the processing plant is a labour intensive and quality critical part. The damage to live birds in this process, resulting in downgrading of carcasses, is a well known problem. Also the labour involved, both in the ergonomie and economic sense, is a compelling motive for new developments, in spite of several semi-automated systems that are operational today. The same applies to unloading and shackling at the start of the slaughterline.

Slaughter line

The slaughtering section of the processing plant has almost been fully automated, saving a lot of manual work; a welcome development from the ergonomie and economic points of view. From the quality side, however, several critical remarks can still be made:

Stunning The electrical water bath stunning causes substantial damage to the meat quality. This is mainly caused by vein ruptures and bone breakage. Trials (and errors) with a variety of currents, voltages and stunning time has so far not lead to any acceptable improvement. This stunning damage has become more visible and resulted in more downgrading, since more cut-up and deboned products are produced. On the other hand, electrical stunning has been reconsidered by the animal welfare movement, that calls for stun-to-kill practice in order to ensure a fast, painless and stressless unconsciousness of the birds. Altogether, this step in the slaughter line, is in desperate need for improvement and/or replacement by alternative methods.

Scalding The' scalding process, the submersion of carcasses for some time in warm water, shows very little of a modern, high tech and clean operation. On the contrary. Critics of poultry processing hygiene conditions speak of a submersion in "fecal soup" and an ideal solution for cross contamination; if that was the purpose! In other words, the scalding process is a notorious hygienic problem. Maybe, that coming EEG hygiene legislation provides extra momentum to the development of combined spray- scalding and plucking -a Spelderholt development- or to counter-current scalding and/or washing/ decontamination methods.

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Plucking At line speeds of over 4000 bph, at soft scalding temperatures, it is difficult to compromise between removal of all feathers and damage to the epidermis. A lot of force is needed to remove feathers from sock, wing and tail. This force easily damages the epidermis of the most exposed parts of the carcass like breast and drumsticks. A complicating factor is the line speed itself. At 5000 bph, the carcasses are pulled through the plucker at ± 1 km/h. At this speed, more damage is done to the epidermis of the side of the carcass that enters first into the pluckers. On the "lee-way"-side of the carcass the damage is considerably less, as illustrated in Table 1.

Table 1 Rankorder sums*, according to Wilcoxon Rank Sum test, for left and right legs of 20 carcasses, ranked 1 to 40 from slight to serious epidermis damage.

1 | time

j 08.30 jll.00 j14.00

line 1 **

left leg

512 505 561

j right leg

j 308 j 315 j 259

1 line 2 ** |

left leg

275 313 329

1 i | right leg |

| 554 j i 507 1 1 491 1

* Distribution 334-486 is significant at 5% confidence level

** Line 1 - left leg first entering the pluckers Line 2 - right leg first entering the pluckers

Evisceration line

The automated evisceration line has achieved a high performance. Labour has virtually been eliminated, except for giblets harvesting. From the quality side, however, the automation has not achieved the "no defects" status. In the first part of the evisceration line, vent cutting, opening and evisceration can perform well. Even the once critical point of damage to the intestines and subsequent carcass contamination can be avoided by careful regulation of the module.

The only critical point still left, has to be considered together with the head removers and refers to damage to the crop and subsequent contamination of the inside of the neck skin and breast.

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In the ideal situation the head remover cuts the esophagus at 3-4 cm from the crop. This piece of the esophagus will prevent the contents of the crop from contaminating the carcass. On the evisceration unit the crop has to be removed without rupture or other damage. In this way, contamination through crop contents with elevated entero-counts, can be greatly reduced. This fact, together with the avoidance of intestinal contamination and subsequent elevated faecal colicounts, leads to a better microbiological situation.

The second part of the evisceration line consists of inspection modules: inner neckskin inspection (crop-bore), inside-outside washers, neckskin cutters and vacuum airsac membranes remover, all contribute to the final cleaning and dressing before the carcass enters the cooling section. In the evisceration section only giblets harvesting and veterinary inspection are nowadays the line-bound operations left.

In recent years, there has been a development to carcass-grading systems, that also operate on this evisceration line. This quality grading refers to visible carcass quality, such like litter-related skin abnormalities, feed withdrawal and transport damage. This quality judgement is a full-time job in order to cover all these aspects in a statistically responsible way.

As this quality grading may involve also financial consequences there is a wish for an objective, instrumental measurement, that covers every bird, and replaces quality inspectors. Maybe that modern vision technics can automate this quality grading process in the near future. One step further then is to identify each defect with the carcass line position and direct those carcasses with defects to cut-up lines where the selection of the defect part is automatically performed on the processing module.

Cut-up lines

In the cut-up lines we have seen many developments over the last decade. From the former line-bound manual operations, almost all the different cuts can now be done on automated lines with special modules for the cutting and deboning processes. So far so good, as once again this automation brought considerable ergonomie and economic advantages. From the quality point of view this development is not yet finished and has to meet still higher specifications. Legislative-, yield- and marketing considerations require true anatomical cuts, which today are either not available or lack sufficient reproducibility.

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Most of the cut-up work is performed with circular blades, that cut in one plane. Anatomical cuts are more complex, as everyone who tries to cut-up a carcass with a knife will confirm. This leads to a "less then perfect" performance, that still feeds the discussion with the module designers over for instance: - a piece of the back bone left on the leg, even when cut in the hip-joint - breast meat left on the ribs and wishbone - breast meat, cut with the wings - thigh meat left on the backbones, etc.

In our opinion this discussion will continue, and improvements will emerge until well into the next century.

In the present situation the performance of the automated cut-up lines depends heavily on the weight range presented. For most of the cuts, a weight range of ± 25 g is needed to reach an acceptable compromise between reproducibility, yield and quality. To reach such an acceptable compromise, given the weight distributions between and within flocks of broilers, one solution uses flexible steering possibilities, disconnected from the main weight distribution line, and, in general, an overcapacity of cut-up modules, tailored to the maximum offer of specific weight ranges. Such a system of course, has to operate without the manual re-hanging necessity and avoid the troublesome buffer-build up, maintaining in stride the important first-in first-out principle.

Packaging

The presentation of poultry and poultry products is year after year becoming more important in the marketing of this commodity. For the packaging itself a wide variety of machines and materials exists; and new options are presented frequently.

In this section there is still a considerable amount of manual labour involved, mainly for the product arrangement on trays and boxes, and subsequent handling of the trays.

Automation options in this area have been scarce so far, but in co-operation with the disciplines of machine building and packaging systems development, also this part of the production will find its automated solution.

369

Distribution

The ideal situation for the distribution of a perishable food commodity is to know exactly what the consumer wants to eat tomorrow!

But, as we all know, the consumers' behaviour is as unpredictable as the weather.

Still, based on forecasting experience and computerized processing of orders, production orders, order picking sequences and distribution routes, the availability of poultry products at the numerous selling points scores more then average. But still not good enough, as (half) empty food shelves in shops sometimes demonstrate. Maybe, that the prediction of consumer behaviour and the supply of poultry products accordingly is the ultimate automation in poultry processing.

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LOGISTICS - PLANT DESIGN AND EQUIPMENT

J.W. Beeftink

Stork PMT B.V. , P.O. Box 118, 5830 AC Boxmeer, The Netherlands

Abstract

Considering poultry plant logistics, the application of new technical solutions is a challenging task for the machine manufacturer. Stork PMT developed a tool for assessment and synthesis of in-plant logistical systems. It proved to be a necessary step for successful implementation of machines and technology.

Introduction

After quality and product development logistics is now increasingly regarded as a significant weapon in the competitive struggle. The market demands an ever-increasing range of products and individual requirements, e.g. regarding packaging, are becoming more and more specific. By the same token a shorter delivery lead-time, longer shelf life and good customer service level are expected as natural qualities from a processor of fresh products (see Figure 1).

In many plants the time is right for a thorough review and adjustment of logistic systems. It's management is no longer subordinate to production, but often assigned to an independent position or department.

This development is paralleled by a growing need for expertise and specialist assistance in determining the plant design and optimizing data processing and organization. A number of factors have induced Stork to assume the role of consultant and educator; a fairly unique development in the world of machine builders, which brings unique possibilities as well as risks.

- Expert knowledge in this field is scarce, even in international literature. - In this industry, organization and logistical possibilities are to a high extend determined

by plant design.

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- Determining plant set-up without an evaluation of all related factors, including options for information and organization, will lead to suboptimization on the basis of available technical solutions and thus also to disappointing results.

- The poultry processing industry has a reputation of effecting developments in the field of automation and technology in close co-operation with it's suppliers.

- Contrary to other food processing industries consultancy agencies are rarely called in for determination of plant set-up. Expert consultants for this sector are few and far between and due to their lack of insight into the latest developments. Their recommendations are usually only of moderate quality and without detail.

The logo (Figure 2) especially designed for this Stork activity visualizes the integration of technology, organization and information around a diverging flow of goods.

Systematic logistical analysis

Next to the development and implementation a number of sophisticated technical solutions, the main requirement was for a method that would provide a quick survey of the options, demands and bottlenecks as well as a structured draft plan for logistic systems. In a number of instances the age old sales talks conducted whilst studying the lay-out drawings no longer proved effective. Very often one loses track of the overall picture on both sides, which only encourages suboptimization.

The structured method for analysis developed by Stork provides a guideline which allows the aspects relevant for plant set-up to be distilled out quickly. Possible organizational and information bottlenecks can be rooted out. Giving careful consideration to the logistical concepts that can be applied in the industry constitutes an important step. Stork finally defined 5 different concepts that depending on company environment can be applied.

Now after two years of development and implementation the results are very encouraging. Frequently an integral solution can be offered within a brief period of time, which, despite the elaborate research that preceeds it, will save time for all those involved. A drawback to this approach lies in the commercial aspects, the trust and above all the stringency and efficiency with which the various interviews must be conducted. In nearly all cases at least 3 (in extreme cases as many as 8) numbers of staff were needed to obtain a consistent picture. Generally speaking, the people involved were not used to discuss bottlenecks and possible solutions in this way, with their colleagues.

Possible objectives for a "logistic optimization" project in case of an extension, new plant or reorganization could be:

372

- Increasing productivity by preventing unnecessary transport, handling, searching and the like. A number of examples can be given. In certain areas productivity can be improved by as much as 50%.

- Decreasing stocks and product-in-process volume. - Increasing clarity and controllability of the process thus decreasing the amount of

overhead personnel. - Increasing the use of available sources in bottleneck areas. - Increasing customer service level. - Reducing throughput time for project planning of execution. - Implementation of well thought out emergency procedures.

Figure 3 gives a simplified representation of the final results of research conducted in the processing plant shown in Figure 1.

Current status of data processing and mechanization

Especially in the field of technology there is a clear trend towards further flexibility in in­line functions. Very often, however, the extreme flexibility, that is regarded as desirable at the start of a project, turns out to be a suboptimization when viewed in the light of integral approach.

Establishing measuring points along the "uncertain" track of the processing plant, i.e. from the growing farm to the product distribution, is a slow process. There is room for further improvement in the future, especially with regard to the controllability of the processing plant.

In an environment in which the period between placing an order and the time of delivery (delivery lead-times) is steadily decreasing, a proper forecast, planning structures and flexible customer order handling are the only options for a sensible production method. However, the application of these techniques is still not very widespread. The options and techniques for automatic identification, recording and coding of final products were sufficiently crystallized out in other sectors to allow large scale application. Here again it applies that their introduction is a slow process, as most of the time there is no integral approach. New regulations for product reliability will greatly encourage such developments. The effect of these rules will no doubt be that a number of logistic concepts, and therefore also options for plant set-up, can no longer be applied.

373

Figure 1

Figure 2

| 0 \ toi

pu}

374

Figure 3

375

376

FLEXIBLE AUTOMATION: TRANSPORT OF INDIVIDUAL SHACKLES

H. Hiipkes

Machinefabriek Meyn B.V., P.O. Box 16, 1510 AA Oostzaan, The Netherlands

Abstract

The development of automation in poultry processing plants and recent developments like a flexible automation system and the possibilities of such a system are described.

Introduction

"Automation" is an often used word with various meanings. Within the scope of this paper, there will be assumed no difference between mechanization and automation although for the industry the difference is quite big.

"Flexible" means the possibility to adapt to different circumstances. The definition of the circumstances is important to find the correct meaning of flexible. For instance, a processing plant can be flexible in being able to handle one day broilers and the other day turkeys on two completely different processing lines with no flexibility at all.

A specialized broiler processing plant is not able to process (reasonably) other poultry, but may be able to process variable flocks of broilers into different types of end product (high scalded, waterchilled, deep frozen whole birds vs low scalded, airchilled (fresh product).

"Transport of individual shackles" indicates, that this paper is focussed on the development of the internal transport of the birds to be processed i.e. the overhead conveyor with the shackles into which the birds are hung.

All the individual processes and machines to which the birds are exposed are developments in itself and may have influence on the type and function of the overhead conveyor and its shackle.

377

Automation

Already in about 1925 the processing of poultry becomes subject to increasing capacities and an ongoing pressure to mechanize, to automate does exist ever since.

The development of the first overhead conveyor to transport birds through a scalding tank was the start of automation of transport. The first fase ended with an overhead conveyor line to which live birds are hung and transported along the several processes like stunning, killing, bleeding, scalding, plucking, head removal, evisceration and cutting of the hocks before entering the water chiller. Such a line is still produced as semi-automatic processing line and can be characterized as an overhead conveyor that transports a bird along the several semi automatic or manual processes. The second fase of automation started with the development of machines, that perform a certain action to the individual birds with the transport system in a synchronized way. It causes the overhead conveyor to change from a transport system into a transport and drive system. Due to the higher demands the lines had to be made shorter and at logical points in the process birds were dropped off from one line and transported to the following process line.

The end of this fase is characterized by a 6.000 bph processing plant existing out of 1 killing line, 1 evisceration line, 1 evaporative air chilling line, 1 weighing line and two or three cut-up lines.

At all connecting points birds were dropped off and rehung.

The third fase can be characterized by automatical rehanging from one line to the other line. During the last 10 years a number of automatic rehangers were developed, with or without hock-cutting, and more recently even with or without weighing which makes it possible to follow an individual bird from the live bird hanging station. Up to the cut-up line where parts are removed from the remaining carcass without being dropped. An increasing problem became the sensibility of equipment for "standard" bird sizes. Killing and evisceration lines can normally handle flocks with a VC of 10-15% (sometimes flocks with a genetic variance of 20% VC are brought to a processing plant with the expectation, that the plant will "easily", "automatically" fix it). Cut-up lines in general do need a VC of about 4-8% to perform, which is realized by weight-sorting.

378

Flexibility

From marketing point of view an increasing pressure was put on production to be able to produce faster according to later available sales information. It was clear, that to meet these demands more different cut-up lines would be needed and selection should not only be possible according to weight, but also according to quality parameters. Furthermore, the products before cut-up should not be buffered by dropping off into bins and individual machines and lines should be automatically bypassed by products so a disturbance in one of the machines would not automatically hold up the total processing line.

One of the firs things to realize is that flexibility needs freedom of action and almost automatically requires an overcapacity in production facilities.

For instance only one cut-up line of 4.000 bph for the total capacity does not give any flexibility. Two cut-up lines, each with a capacity of 4.000 bph but running at 2.000 bph do realize already the possibility of increasing the speed of one line if the other by what reasons comes to a stand. At the same time an average attractive packaging and cut-up department would like to pack whole birds up to 40% of production capacity, to cut up to 100% of the production capacity, so that in total installed capacity would be at least 140% of the nominal capacity.

One of the next demands became the need for resorting the saddles of the carcasses by weight after cutting off the wings, breastpart and backbone. In this way the inevitable available extra inaccuracy of the wingcutting and breastcutting process can be corrected by reweighing and resorting the saddles.

It was decided, that all these rehanging demands in combination with the "normal" rehanging of efficiency (100% is technically impossible) did ask for a new approach, namely rehanging of shackles.

Rehanging of shackles

It is well known in the mechanizing industry, that products difficult to handle or to be transported are connected to carriers. In this way the transport function is taken over by the carriers and the product remains part of the carrier throughout (a part of) the process. In the present case it was decided to change from transporting birds from one shackle to another in to transporting shackles.

379

The development started for a cut-up department after the airchill tunnel but is now available from the end of the evisceration line.

In the first place it meant a complete new transport system, in which shackles can be taken out of a conveyor line and put onto another conveyor line.

A buffer system had to be developed. Due to the conflicting demands to a shackle, easy to rehang and easy to buffer, a kind of hybride shackle was developed that is able to be hung into a conveyor line. In this way it was possible to use a drive-free buffer system.

Normal electronical tracking systems follow shackles and products via shift registers and counting. Over longer distances and variable pitches this becomes more and more complex. So a system was used in which the shackle is coded, information can be added to this code and can be read out from the shackle in a fast way.

This information can be gathered automatically (e.g. weight via automatic weighing systems) or by hand (e.g. grading information).

On every switch point this information can be read out, compared with a program and a decision is made in what direction the shackle is send.

Flexible automation

Now mechanically the functions are available to introduce flexibility into a plant. But as always, the infrastructure, the logistical planning, the production planning and the management decisions have to be introduced into a control system to be able to use the flexibility in an attractive way. The first fase than is to develop a program that includes the normal production and logistical planning. In fact this is nothing more or less than the day to day routine of the processing plant.

To be able to make fast changes more, accurate and first information is necessary to be able to find out whether alternatives are possible or not. It does create the actual need to know the status quo of every machine, every switch point and every other relevant situation throughout the plant. When this information is made available, certain decision making processes can be automated. For instance, the whole birds are weighed, graded and divided over three whole bird packing lines and four cut-up lines.

One of the whole bird packing lines runs into a temporary problem. This will first cause a buffer to be filled. When the buffer is full, the program will automatically reroute the birds to other lines according to preprogrammed alternatives. The remaining lines can be speeded up if necessary and all the birds remain processed up till the moment the packaging line is put into order again and the original program is executed again.

380

Conclusion

Flexible automation is an integration of management and technical possibilities. For poultry processing plants after the evisceration lines, the development of transferring shackles created a whole new serie of possibilities to develop production programs, that can be controlled in a flexible way.

381

382

INLINE COLOR MEASUREMENTS OF BROILER BREAST MEAT

J. Sjollema and P.C.F. Borsboom

Sensoptic B.V., Stationsweg 10, 9921 PV Stedum, The Netherlands

Abstract

The value of color measurements on broiler breast meat can be twofold: the color of meat is indicative for the post-mortem stage during processing and color measurements can be included within a standard quality measuring procedure at the end of the processing line. This paper describes the principles of instrumental meat color measurements using the CTM technique as developed by Sensoptic B. V. As an illustration two series of inline measurements on broiler breast meat are described, which indicate that color might be indicative for specific postmortem processes and chilling effects. In addition recommendations are made concerning the development of a meat color standard for use in poultry meat color classification as an end-quality measure.

Introduction

The quality of broiler breast meat can be determined in terms of e.g. tenderness of the separate muscle groups, color, waterbinding properties, hygienic condition, blood spots, pH. These quality parameters are variable, partly as a result of processing parameters (transportation, chilling conditions and time of deboning) partly as a result of the genetic origin and food conditions. Therefore a need can be observed to determine the quality of poultry meat as a measure of the quality of the slaughtering process, as a prediction of the final quality and as a measure for the price of the purchaser as well as the consumer. One of the interestig parameters characterizing the quality of poultry meat is the color. The color, and especially the variation of color within one package and the occurrence of bloodspots is an element of quality which influences the customer as well as the process industry. The problem has been mentioned already in the poultry industry but has not yet been solved.

383

In addition to the measurement of the final product quality, product parameters could be defined which describe the specific stages in the post mortem process. Among pH, temperature, and passive electrical characteristics, meat color can be an indicating parameter as well, because light scattering showed to be closely related to the sarcomere length, which tends to change during the post-mortem process. In this paper an overview will be given of the state of the art for color determination on broiler breast meat. The principles will be presented of an instrumental color measuring system for as well invasive as non-invasive color measurement. As an illustration a series of color measurements will be discussed. The aim of the measurements was to investigate whether or not color can be a valuable process parameter along with pH and temperature. A second aim was to find out whether color is an indication of sarcomere length, which showed to be closely related to the tenderness of meat (Papa and Fletcher, 1988). Finally the paper contains a recommendation for using a color standard as a calibration of color-classifications at the end of the processing line.

Materials and Methods

Principle of meat color determination by using the C.T.M. technique

Color is a more or less sensoric parameter, which is difficult to quantify or to translate into instrumental values (Billmeyer and Saltzman,1981). Usually color is expressed on basis of three parameters (CIE*-Lab coordinates): L* represents the lightness of a material, a* represents the intensity of the color red and b* represents the intensity of the color yellow. The lightness of a material is mainly determined by scattering of the material (in the case of meat the length of cell structures is a determining parameter) and the mean absorption of the material (absorption over the entire visual spectrum) a* and b* are determined by specific absorption in a spectral region (e.g. absorption of green light by (oxy)myoglobine in meat). Instrumental determination of these color coordinates is possible by using reflection or transmission spectroscopy. Meat color is mainly correlated to the L* value, the other parameters are less valuable. There are, however, in general main objectives against color measurements using reflectometric methods. - Using reflectometric instruments volume reflected light originating from the

illuminating light source will not only reflect into the detection area, but will also escape sideways from this area. This so called edgeeffect will cause major spectral deficiencies in the red area.

- Specular reflection disturbs the reflection spectrum, specifically at very smooth surfaces.

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