SALT CONCENTRATION AND SPECIES AFFECTS PROTEIN

SALT CONCENTRATION AND SPECIES AFFECTS PROTEIN EXTRACTABILITY AND PROCESSED MEAT CHARACTERISTICS

BY

BRIANNA DAWN KEEVER

THESIS

Submitted in partial fulfillment of the requirements for the degree of Master of Science in Animal Sciences

in the Graduate College of the University of Illinois at Urbana-Champaign, 2011

Urbana, Illinois

Adviser:

Professor Anna Dilger

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Abstract

Excessive sodium consumption is one contributor to high blood pressure and

cardiovascular disease, and the Institute of Medicine has recommended that salt levels be

reduced in food, including processed meats. As such, it is critical to understand the interaction of

salt level and meat species with regards to characteristics of further processed meat. Salt-soluble

protein extraction, important in forming meat emulsions, is dependent on several factors

including species of protein source. As such, the purpose of our first study was to quantify the

amount of salt-soluble proteins in various muscles of three species commonly used in meat

products - beef, pork, and chicken. Pork and beef serratus ventralis (dark) and semitendinosus

(light) muscles, and chicken pectoralis major muscles (light) and the entire thigh (dark) were

used. Samples were analyzed for salt-soluble protein content at salt (NaCl) concentrations

ranging from 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, to 3.5%. Overall, there was an increase in

extractable salt-soluble protein content as the salt concentration increased. The interaction of

species and salt showed all species were different (P < 0.05) from one another when compared at

the same salt concentration when corrected for fat and moisture content with chicken showing

the greatest extractability. In chicken, extractable salt-soluble protein was increased (P < 0.01)

in light muscles compared with dark muscles. In industry, most processed products include 1.5-

3.5% salt, and at these levels we have demonstrated that chicken meat had more salt-soluble

proteins to aid in the processing of meat products. Given the advantage of chicken overall and in

chicken light muscles compared with dark muscles, the purpose of the second study was to

evaluate characteristics of products manufactured from pectoralis major muscle (light) and the

entire thigh (dark) of chicken. The study was designed as a complete randomized design in a

2x4 factorial arrangement with factors of muscle type (light and dark) and salt concentration

(0.5%, 1%, 1.5%, and 2%). Bologna was manufactured and analyzed for salt-soluble protein

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content, proximate analysis, cooking yield, pH, Minolta L*, and binding strength. In thigh

muscle bologna batches, raw and cooked moisture content, as well as cooked fat content, was

increased over breast muscle batches (P < 0.01). Increased retention of moisture in thigh muscle

bolognas contributed to improved cooked yields compared to breast muscle bolognas (P = 0.01).

We were especially interested in whether characteristics of low-salt (≤ 1%) light muscle

bolognas were similar or superior to higher salt (≥ 1.5%) dark muscle bolognas. Therefore, we

used a single degree of freedom contrasts to compare these products. Low salt breast bolognas

exhibited slightly higher (0.05 percentage units) salt-soluble protein extractability (as a

percentage of crude protein) compared with higher salt thigh meat bolognas. The increase in

salt-soluble protein content, however, was not reflected in a higher break strength value for low-

salt breast bologna compared to high-salt thigh bologna (P < 0.01). Hardness increased in low-

salt breast bologna compared to high-salt thigh bologna (P < 0.01). Low salt breast bologna

showed acceptable processing characteristics and textural properties, therefore it can be used to

manufacture low salt products.

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Table of Contents

Chapter I Review of Literature ...................................................................................................... 1

Introduction ............................................................................................................................. 1

Protein Extraction .................................................................................................................... 2

Formation of Meat Emulsions ................................................................................................. 3

Gelation ................................................................................................................................... 4

Sensory .................................................................................................................................... 6

Objectives ................................................................................................................................ 6

References ............................................................................................................................... 8

Chapter II Extraction of Salt-soluble Proteins in Meat is Affected by Species and Muscle Type....................................................................................................................................................... 11

Abstract .................................................................................................................................. 11

Introduction ........................................................................................................................... 11

Material and Methods ............................................................................................................ 13

Results and Discussion .......................................................................................................... 15

Conclusions ........................................................................................................................... 18

References ............................................................................................................................. 19

Tables and Figures ................................................................................................................. 21

Chapter III The Effects of Varying Salt Concentrations on Protein Solubility and Product Characteristics of Bolognas Manufactured from Chicken Muscles ............................................. 25

Abstract .................................................................................................................................. 25

Introduction ........................................................................................................................... 25

Materials and Methods .......................................................................................................... 26

Results and Discussion .......................................................................................................... 30

Conclusions ........................................................................................................................... 34

References ............................................................................................................................. 35

Tables and Figures ................................................................................................................. 38

1

Chapter I

Review of Literature

Introduction

Today’s consumer devotes less time to preparing meals, so they look to ready-to-eat

products to reduce time spent in the kitchen. However, these products traditionally tend to be

higher in sodium (975mg sodium/100g), than unprocessed meat, such as steaks or roasts (50-90

mg sodium/100g) (Romans, Costello, Carlson, Greaser, and Jones, 1994). In 2010, the Dietary

Guidelines for Americans listed reducing sodium as a major goal (USDA and USDHHS, 2010).

In addition, the Institute of Medicine recommends that intake of sodium not exceed 2300 mg per

day for people over the age of 14. At this level of intake, sodium is not likely to trigger adverse

health effects, such as increased risk of developing hypertension (Dahl, 1972). However,

average sodium intake for Americans over the age of two is approximately 3400 mg per day,

nearly 1.5 times more than recommended levels (USDA-ARS and USDHHS-CDC, 2006). Thus,

it is imperative that consumers lower sodium intake as one way to ensure a healthy lifestyle. In

response to desires for lowered sodium, meat processors offer products with reduced sodium

levels. The challenge for the industry, however, is to create high-quality products that remain

acceptable to the consumer despite reductions in salt.

Salt, defined in this paper as sodium chloride (NaCl), was initially used by people to

preserve meat. Currently, salt is the most widely used non-meat ingredient in processed foods

and functions to enhance the flavor and texture of meat products. Terrell (1983) described the

following to be advantages of salt addition to meat products: extraction of proteins to increase

hydration and water binding capacity, increased binding properties of proteins to improve

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texture, increased viscosity of meat batter facilitating the incorporation of fat to form stable

batters, increased pH of meat systems, flavor enhancement and bacteriostatic effects.

Protein Extraction

Muscle protein is categorized into three classes of proteins, differing in function and their

ability to be solubilized in salt solutions. The first class, sarcoplasmic proteins, account for

approximately 30% of total muscle proteins and are soluble at low ionic strength (>0.3mM)

(Scopes, 1964). Proteins from the sarcoplasm, including myoglobin and metabolic enzymes

make up this class of proteins. The second class of proteins is the myofibrillar proteins, which

comprise approximately 50-60% of muscle proteins and are soluble at salt concentrations greater

than 0.3M. Myosin and actin contribute 45 and 20%, respectively, to the total myofibrillar

protein content making these two proteins the most important when considering protein

extraction in further processed products (Scopes, 1964). The third class of proteins is known as

the stromal proteins, which are not soluble in salt solutions unless heat is added. These stromal

proteins constitute approximately 10-20% of the total muscle proteins and consist of collagen

and elastin.

Further processed meat products typically begin with a primary comminution (reduction

of particle size) phase. Comminution is essential in disrupting membranes and sarcolemma of

muscle in order to free myofibrillar proteins and allow them to swell. After comminution, salt is

added, increasing the water-binding capacity of myofibrillar proteins by creating a downward

shift in the isoelectric point of these proteins, resulting in a larger net negative charge. Hamm

(1961) theorized that salt caused a repulsion of peptide chains on myofibrillar protein, allowing

water to enter this space. As the concentration of salt incorporated in products increases, the

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amount of myofibrillar protein extracted increases until a threshold is reached at 1.2 M NaCl

(Munasinghe and Sakai, 2004). Salt extraction of proteins is affected by pH, extraction volume,

and homogenization time (Lan et al., 1993). The ideal extraction for beef and pork occur at a pH

of 6.0 with an extraction volume of 15 X sample weight and a homogenization time of 90 to 120

seconds (Lan et al., 1993). Extraction also differs between species and muscles within species.

Under ideal extraction conditions, pork longissimus dorsi muscle yielded greater values for salt

soluble proteins as a percent of the sample weight when compared to that of beef longissimus

dorsi muscle and semimembranosus muscle (Lan et al., 1993). The content of extractable salt-

soluble proteins was highly variable due to differences in pH and collagen content among red

meats commonly used in the manufacturing of further processed meats. Cow meat had the

highest extractability (8.19%) and meat classified as “rework”, the lowest (1.23%) (Saffle and

Galbreath, 1964). However, many studies have established that greater amounts of salt-soluble

proteins could be extracted from breast muscles of poultry (turkeys, chickens, and ducks) when

compared to the leg muscles of the same animals (Khan, 1962; Hudspeth and May, 1967; Maurer

et al., 1969; McCready and Cunningham, 1971; Prusa and Bowers, 1984; Richardson and Jones,

1987). Constrained by the type of product being manufactured, the extractability of salt-soluble

proteins is highly variable and dependent on several processing factors, such as pH and time.

Therefore, it is important to characterize the extractability of different species and muscles to

identify where they can best be used in further processed products.

Formation of Meat Emulsions

The ability of salt to solubilize myofibrillar proteins is one of the most important factors

in the processing of emulsified meat products like bologna and frankfurters. These products are

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formed by blending a mixture of lean meat, fat, water, salt and other ingredients into an emulsion

forming a nearly homogenous product. Meat emulsions form a two-phase system with the

dispersed phase containing fat particles and the continuous phase consisting of suspended

proteins and water containing dissolved salts (Forrest et al., 2001). In this system, solubilized

proteins add stability to the emulsion, acting as emulsifying agents and reducing surface tension

formed when fat comes into contact with water (Schut, 1976). Solubilized protein molecules

coat fat particles through protein’s affinity for both hydrophilic and hydrophobic particles.

Protein molecules, once unfolded, are oriented around fat particles with hydrophobic side chains

in contact with fat and hydrophilic side chains in contact with water (Forrest et al., 2001).

Increasing the amount of solubilized protein will lead to an increase in the emulsion stability of

the product, which is a measure of the ability of the emulsion to retain fat and water (Zorba et al.,

1993). Also, increasing the solubilized protein concentration will lead to an increase in the

emulsion capacity of the product, which is a measure of the ability of the emulsion to

encapsulate fat (Swift and Sulzbacher, 1963). Although, bologna and frankfurters are classified

as emulsions, they are not true emulsions. When making frankfurters not all of the fat particles

in the system were uniformly surrounded by solubilized proteins leading to a more

heterogeneous mixture than a true emulsion (Swasdee et al., 1982).

Gelation

After the emulsified product is placed into a casing, it is thermally processed allowing for

muscle protein gelation to occur. The gelation of proteins in comminuted products is responsible

for adhesion of meat to meat as well as binding fat particles within the meat. The process of

forming this gel matrix takes place in three steps: the initial denaturing of proteins; the

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aggregation of these individual proteins, and the crosslinking of the protein aggregates to form a

continuous network after heating (Xiong, 2004). The ability of these myofibrillar proteins to

form a stable gel matrix is influenced by structure, size, concentration and pH of the protein. It

has been demonstrated that intact myosin contributes to the binding properties of gels and that

actin alone cannot influence these properties (Samejima et al., 1969). However, the presence of

actin at a myosin to actin ration (w/w) of 24 increased rigidity of gels when compared to gels

prepared in the absence of actin (Morita and Ogata, 1991). The balance of proteins within a

muscle also influences gel stability. Muscles containing large amounts of connective tissue are

detrimental to the formation of a stable gel matrix due to their poor emulsifying properties and

the propensity to shrink during the heating process. Therefore, the amount of myofibrillar

proteins extracted in relation to the amount of collagen will influence the quality of the finished

product.

Muscle type and pH influence gel stability and these factors interact with each other.

Myofibrillar proteins from white muscles are able to form firmer gels than those from red

muscles due to the differences in myosin isoforms (Xiong, 1994). Gels formed from chicken and

turkey pectoralis muscles (predominantly white) were more rigid and less influenced by pH than

gels formed from chicken leg muscles (predominantly red) (Foegeding, 1987; Xiong and

Blanchard, 1994). Chicken breast muscles formed the strongest gels at a pH of 6.30, while the

thigh muscles were strongest at 6.00 (Xiong and Brekke, 1991; Lesiow and Xiong, 2003). Pork

longissimus dorsi muscles (predominantly white) were also able to form stronger gels when

compared to pork serratus ventralis muscles (predominantly red) (Robe and Xiong, 1993). In

contrast, beef semimembranosus muscles (predominantly white) and vastus intermedius muscles

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(predominantly red) gels showed no differences when compared at similar pH (Vega-Warner et

al., 1999). The ability to target the use of muscles at their optimum gelation pH and salt

extraction level in further processed products would enhance the emulsion stability.

Sensory

One of the challenges to reducing the inclusion level of salt in further processed products

is consumer acceptability of lower sodium products. Consumers may not find the new flavor or

textural properties to be similar enough to the products they are accustomed to eating. This is

further complicated by the dual pressure to reduce the fat content of processed products as the

combination of fat and salt in further processed products contributes many of the sensory

characteristics found within these products (Ruusenen et al., 2003). Salt reduction, however, is

possible while maintaining sensory properties. Panelists found the same degree of saltiness in

hams containing 1.7, 2.0, and 2.3% salt (Ruusenen et al., 2001). Similarly, frankfurters could be

manufactured with 1.3% salt and still maintain sensory hardness scores deemed previously to be

acceptable to consumers (Matulis et al., 1995) and with no adverse effects to the physical

properties of the product (Puolanne and Terrell, 1983a, 1983b). However, salt inclusions of less

than 1.0% in frankfurters yielded poorly due to a lack of water retention (Puolanne and Terrell,

1983a, 1983b). The ability to reduce salt and maintain textural properties has been shown to a

degree, however, to continue the reduction of salt and maintain acceptability gradual reductions

may need to be made over a period of time.

Objectives

The purpose of this study was to identify species or muscles that would allow for salt

reduction while maintaining acceptable protein extraction and product characteristics. The

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species of interest are beef, pork and chicken because these species are commonly used by the

meat industry for further processed products. It is expected that chicken will yield the highest

amount of total extractable salt soluble proteins based on previous literature, however it is

unclear what differences will be observed between beef and pork. Within a species, differences

between muscle types and their suitability for further processing will also be determined. By

identifying differences in extractability of salt soluble proteins that may exist between common

livestock species such as beef, pork and chicken or between muscles, meat processors could

choose protein sources that allow maximum myofibrillar protein extraction at reduced salt

inclusion levels.

The objectives of this study were:

1) Quantify the amount of salt-soluble proteins in beef, pork, and chicken.

2) Determine further processed characteristics of products from white muscle and

dark muscles over a range of salt inclusion levels.

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References

Dahl, L. K. (1972). Salt and hypertension. The American Journal of Clinical Nutrition, 25, 231-244.

Foegeding, E. A. (1987). Functional properties of turkey salt-soluble proteins. Journal of Food

Science, 52, 1495-1499.

Forrest, J.C., Aberle, E.D., Gerrard, D.E., and Mills, E.W. (2001). Principles of Meat Science

Fourth Edition edn. Dubuque, IA, Kendall/Hunt Publishing Company.

Hamm, R. (1961). Biochemistry of meat hydration. In C.O. Chichester and E.M. Mrak, Advances

in Food Research (pp. 355-380) Academic Press.

Hudspeth, J. P., and May, K. N. (1967). A study of the emulsifying capacity of salt soluble proteins of poultry meat. Food Technology, 21, 1141-1142.

Khan, A. W. (1962). Extraction and fractionation of proteins in fresh chicken muscles. Journal

of Food Science, 27, 430-434.

Lan, Y. H., Novakofski, J., Carr, T. R., and McKeith, F. K. (1993). Assay and storage conditions affect yield of salt soluble protein from muscle. Journal of Food Science, 58, 963-967.

Lesiów, T., and Xiong, Y. L. (2003). Chicken muscle homogenate gelation properties: effect of pH and muscle fiber type. Meat Science, 64, 399-403.

Matulis, R. J., McKeith, F. K., Sutherland, J. W., and Brewer, M. S. (1995). Sensory characteristics of frankfurters as affected by fat, salt, and pH. Journal of Food Science, 60, 42-47.

Maurer, A. J., Baker, R. C., and Vadehra, D. V. (1969). The influence of type of poultry and carcass part on the extractability and emulsifying capacity of salt-soluble proteins. Poultry

Science, 48, 994-997.

McCready, S. T., and Cunningham, F. E. (1971). Salt-soluble proteins of poultry meat 1. composition and emulsifying capacity. Poultry Science, 50, 243-248.

Morita, J., and Ogata, T. (1991). Role of light chains in heat-induced gelation of skeletal muscle myosin. Journal of Food Science, 56, 855-856.

Munasinghe, D. M. S., and Sakai, T. (2004). Sodium chloride as a preferred protein extractant for pork lean meat. Meat Science, 67, 697-703.

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Prusa, K. J., and Bowers, J. A. (1984). Protein extraction from frozen, thawed turkey muscle with sodium nitrite, sodium chloride, and selected sodium phosphate salts. Journal of Food

Science, 49, 709-713.

Puolanne, E. J., and Terrell, R. N. (1983a). Effects of rigor-state, levels of salt and sodium tripolyphosphate on physical, chemical and sensory properties of frankfurter-type sausages. Journal of Food Science, 48, 1036-1038.

Puolanne, E. J., and Terrell, R. N. (1983b). Effects of salt levels in prerigor blends and cooked sausages on water binding, released fat and pH. Journal of Food Science, 48, 1022-1024.

Richardson, R. I., and Jones, J. M. (1987). The effects of salt concentration and pH upon water-binding, water-holding and protein extractability of turkey meat. International Journal of

Food Science and Technology, 22, 683-692.

Robe, G. H., and Xiong, Y. L. (1992). Phosphates and muscle fiber type influence thermal transitions in porcine salt-soluble protein aggregation. Journal of Food Science, 57, 1304-1304.

Ruusunen, M., Simolin, M., and Puolanne, E. (2001). The effect of fat content and flavor enhancers on the perceived saltiness of cooked bologna-type sausages. Journal of Muscle

Foods, 12, 107-120.

Ruusunen, M., Vainionpää, J., Puolanne, E., Lyly, M., Lähteenmäki, L., Niemistö, M., and Ahvenainen, R. (2003). Physical and sensory properties of low-salt phosphate-free frankfurters composed with various ingredients. Meat Science, 63, 9-16.

Saffle, R. L., and Galbreath, J. W. (1964). Quantitative determination of salt-soluble protein in various types of meat. Food Technology, 18, 119-120.

Samejima, K., Hashimoto, Y., Yasui, T., and Fukazawa, T. (1969). Heat gelling properties of myosin, actin, actomyosin and myosin-subunits in a saline model system. Journal of Food

Science, 34, 242-245.

Schut, J. (1976). Meat emulsions. In S. Friberg, Food Emulsions (pp. 385-400). New York: Marcel Dekker Inc.

Scopes, R. K. (1964). The influence of post-mortem conditions on the solubilities of muscle proteins. Biochemical Journal, 91, 201-207.

Swasdee, R. L., Terrell, R. N., Dutson, T. R., and Lewis, R. E. (1982). Ultrastructural changes during chopping and cooking of a frankfurter batter. Journal of Food Science, 47, 1011-1013.

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Swift, C. E., and Sulzbacher, W. L. (1963). Comminuted meat emulsions: factors affecting meat proteins as emulsion stabilizers. Food Technology, 17, 224-226.

Terrell, R. N. (1983). Reducing the sodium content of processed meats. Food Technology, 37, 66-71.

U.S. Department of Agriculture, Agricultural Research Service and U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. (2006). What we eat in America, NHANES.

U.S. Department of Agriculture and U.S. Department of Health and Human Services. (2010). Dietary guidelines for Americans. 7th edn. Washington, DC, U.S. Government Printing Office.

Vega-Warner, V., Merkel, R. A., and Smith, D. M. (1999). Composition, solubility and gel properties of salt soluble proteins from two bovine muscle types. Meat Science, 51, 197-203.

Xiong, Y. L. (2004). Muscle proteins. In R. Y. Yada, Proteins in food processing (pp. 106-110). Cambridge, England: Woodhead Publishing Limited.

Xiong, Y. L. (1994). Myofibrillar protein from different muscle fiber types: Implications of biochemical and functional properties in meat processing. Critical Reviews in Food Science

and Nutrition, 34, 293-320.

Xiong, Y. L., and Blanchard, S. P. (1994). Dynamic gelling properties of myofibrillar protein from skeletal muscle of different chicken parts. Journal of Agricultural and Food

Chemistry, 42, 670-674.

Xiong, Y. L., and Brekke, C. J. (1991). Protein extractability and thermally induced gelation properties of myofibrils isolated from pre- and postrigor chicken muscles. Journal of Food

Science, 56, 210-215.

Zorba, O., Gokalp, H. Y., Yetim, H., and Ockerman, H. W. (1993). Model system evaluations of the effects of different levels of K2HPO4 NaCl and oil temperature on emulsion stability and viscosity of fresh and frozen turkish style meat emulsions. Meat Science, 34, 145-161.

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Chapter II

Extraction of Salt-soluble Proteins in Meat is Affected by Species and Muscle Type

Abstract

Salt-soluble protein extraction, important in forming meat emulsions, is dependent on

several factors including species of the protein source. The purpose of this experiment was to

quantify the amount of salt-soluble proteins in various muscles of three species commonly used

in meat products - beef, pork, and chicken. Pork and beef serratus ventralis muscles (dark) and

the semitendinosus muscles (light), and chicken pectoralis major muscles (light) and the entire

thigh (dark) muscles were used. Samples were analyzed for proximate composition and for salt-

soluble protein content at salt (NaCl) concentrations of 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, and

3.5%. Overall, there was an increase in extractable salt-soluble protein content as the salt

concentration increased. Chicken had the highest amount of extractable salt-soluble protein

compared with beef or pork at all salt concentrations, when samples were corrected for fat and

moisture content (P < 0.05). Chicken light muscles were able to extract more salt-soluble protein

at most salt concentrations, except 0 and 2.5%, compared with chicken dark muscles (P < 0.01).

This study demonstrates that chicken meat has increased amounts of extractable salt-soluble

protein content compared to beef or pork.

Introduction

Extraction of myofibrillar proteins, commonly called salt-soluble proteins, is crucial in

manufacturing of further processed meat products such as frankfurters and bologna. Once

extracted, these proteins serve as emulsifying agents in meat batter and contribute to emulsion

stability. Extraction is achieved through the addition of sodium chloride to meat. Recently,

however, concerns have emerged in the medical community about excessive sodium intake and

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its relation to cardiovascular disease (Page, 1976; Porter, 1983; Gleibermann, 1973; Tobian,

1997). Therefore, it is in the interest of meat processors to acceptably reduce sodium content in

meat products.

One way to reduce the amount of sodium chloride included in further processed products

is to target meat sources that are enriched in salt-soluble proteins. Greater amounts of salt-

soluble proteins can be extracted from breast muscles of poultry (turkeys, chickens, and ducks)

when compared with leg muscles of the same animals (Khan, 1962; Hudspeth and May, 1967;

Maurer et al., 1969; McCready and Cunningham, 1971; Prusa and Bowers, 1984; Richardson

and Jones, 1987). Under ideal extraction conditions, pork longissimus dorsi muscle yielded

greater values for salt soluble proteins as a percent of the sample weight when compared with

beef longissimus dorsi and semimembranosus muscles (Lan et al., 1993). There were no

differences, however, in salt-soluble protein extraction between beef semimembranosus or

longissimus dorsi muscles (Lan et al., 1993). Our objective was to determine differences in salt-

soluble protein extraction between three species commonly used for further processing – beef,

pork, and chicken and to determine effect of muscle type on protein extraction. For each species,

a predominantly red fiber type muscle (serratus ventralis and entire thigh) and a predominantly

white fiber type muscle (semitendinosus and pectoralis major) were analyzed for differences

within species.

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Material and Methods

Sample Collection

Five muscle samples (approximately 500 grams) were obtained from each of the

following treatment combinations: serratus ventralis (dark) and semitendinosus (light) muscles

from beef and pork, and from pectoralis major muscle (light) and the entire thigh (dark) from

chicken two days post-harvest resulting in 30 total samples. Meat was trimmed of external fat,

homogenized, vacuumed packaged and stored (-29°C) until analyses were conducted.

Proximate Analysis

The moisture and lipid content was determined for each sample using the method

described by Novakofski et al. (1989). In preparation, all samples were trimmed of external fat

and connective tissue, and homogenized using a Cusinart Food Processor. Moisture content was

determined after samples had been placed in a drying oven at 110°C for 48h. Lipid content was

then determined after extraction by washing samples in a mixture of chloroform and methanol.

Salt-Soluble Protein Content

The extractability of both sarcoplasmic and myofibrillar proteins were determined using

the method described by Boler et al. (2011). A master mix extraction buffer of 0.01M 2-[N-

Morpholino]ethanesulfonic acid was used to make the following eight NaCl extraction buffers

0% (0M), 0.5% (0.09M), 1% (0.17M), 1.5% (0.26M), 2% (0.34M), 2.5% (0.43M), 3% (0.51M)

and 3.5% (0.6M) by volume. All extraction solutions were buffered to a pH of 6.0 according to

Lan et al. (1993). Ground muscle samples (0.1 g) were placed in 2.0 mL microcentrifuge tubes

with 4mm stainless steel beads and 1.5 mL extraction buffer. Samples were homogenized

(TissueLyser II, Qiagen Inc., Valencia, CA) for 1 minute. Homogenates were centrifuged

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(Microfuge® 18 Microcentrifuge, Beckman Coulter Inc., Germany) at 15000 x g for 20 min at 4°

C. Supernatants were collected for each sample, diluted 10 fold, and protein content quantified

using a BCA protein assay kit (Thermo Scientific Pierce Protein Research Products, Rockford,

IL). The amount of solubilized protein was determined using a second order polynomial

equation. Data were expressed as a percentage of wet weight and as the percentage of solids

weight (weight minus fat and moisture).

pH

Meat (5g) was placed in a 50 mL conical tube with 20 mL of deionized water and

homogenized (Model PT 10/35, Brinkmann Instruments Co., Switzerland) for 30 seconds. pH

was measured with an automatic temperature compensation epoxy body probe attached to a

bench meter (Model 917001, Model 501, Orion Research Inc., Jacksonville, Florida) that had

been calibrated with pH 4.00 and 7.00 buffers.

Statistical Analysis

Data were analyzed as a randomized complete design in a 3x2 factorial arrangement with

salt as a continuous variable. The statistical model included the main effects of species, salt,

muscle type (light or dark) and their interactions. Differences between moisture, fat, and pH

were determined using MIXED procedure of SAS (SAS Inst. Inc., Cary, N.C.) and means

separated using the PDIFF option with a Bonferroni adjustment. Salt-soluble protein content

were analyzed as repeated measures using an unstructured covariance structure with sample

serving as the subject. Means of salt-soluble protein content were separated with the PDIFF

option with a Bonferrroni adjustment. Differences were deemed significant at P < 0.05.

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Results and Discussion

Proximate Analysis and pH

For moisture content, the main effects of species and muscle type were significant (P <

0.01), however, there was an interaction of species and muscle type (P < 0.01). In beef and

chicken, moisture content was increased in light muscles compared with dark muscles, but in

pork, dark muscle had more moisture compared to light muscles (Table 1). Similarly, for fat

content, the main effects of species and muscle type were significant (P < 0.01), however, there

was an interaction of species and muscle type (P < 0.01). In beef and chicken, fat content was

increased in dark muscles compared with light muscles, but in pork, light muscles had more fat

compared to dark muscles. There is an inverse relationship seen between moisture and fat

content, but this relationship is different for the muscles of pork when compared to beef and

chicken muscles. Generally, it has been accepted that glycolytic (light) muscles contain less fat

when compared to oxidative (dark) muscles since the main energy source of light muscles are

carbohydrate glycogen (Leseigneur-Meynier and Gandemer, 1991). The observed values of

chicken light and dark muscles and beef light and dark muscles were consistent with other

findings (Xiong et al., 1993; Seggern et al., 2005). However, pork muscles did not follow this

trend, perhaps due to the fact that metabolic pathways were more intermediate in the two

muscles examined; still, the observed trend was substantiated by other work (Beecher et al.,

1965).

For pH, the main effects of species and muscle type were significant (P < 0.01), however,

there was an interaction of species and muscle type (P < 0.01). For chicken and beef, pH was

lower in light muscles compared to dark muscles, which was expected due to the method of

metabolism, associated with each muscle type; however, there was no difference between pork

16

muscles. Ultimate pH is dependent on lactate, the final product of glycolysis, which builds up in

muscles after harvest due to stopped blood circulation. Muscles, whose metabolic pathway is

primarily glycolytic like that of light muscles, will produce more lactate, which will drive

ultimate pH downward (Lee et al., 2010). The values observed for pH of chicken, beef, and pork

were consistent with the literature, in that light muscles reported lower values compared to dark

muscles (Xiong et al., 1993; Seggern et al., 2005; Gil, et al., 2008). However, differences in pH

were controlled for when running the salt-soluble protein assay by buffering the solution to pH

of 6.0 for all samples.

Salt Soluble Protein Content

For salt-soluble protein content as a percentage of wet weight, the main effects of species,

salt, and muscle type were significant (P < 0.01), however, there was an interaction of species

and muscle type (P < 0.01), species and salt (P < 0.01), and species, muscle, and salt (P < 0.01).

Overall, increasing amounts of protein were extracted as salt concentration increased (Figure 1).

The increase in extractable salt-soluble protein content as the salt concentration increases is

known as a salting-in effect, and for sodium chloride this effect is seen when salt is added at

concentrations of 0.3 to 1.0 M (Hultin et al., 1995). In chicken light muscles, extractable salt-

soluble protein content increased (P < 0.01) at a more rapid rate with increasing salt levels

compared with all other species and muscle combinations resulting in the interaction of species,

muscle, and salt (Figure 1). Thus, the effect of increasing salt concentrations on the solubility of

muscle proteins is not only dependent on species, but also on muscle type being extracted. The

greater extractability of chicken light muscle compared to chicken dark muscle was in agreement

with other researchers (Khan, 1962; Hudspeth and May, 1967; Maurer et al., 1969; McCready

and Cunningham, 1971; Prusa and Bowers, 1984; Richardson and Jones, 1987). The lack of

17

differences between pork and beef muscles may be due to the increase in the degree of similarity

between muscle fiber types within the muscles, as opposed to the chicken muscles, which were

predominantly type I or type IIb fibers. The interaction of species and salt showed similar

trends, in that, all species were significantly different (P < 0.05) from one another when

compared at the same salt concentration, except for beef and chicken at 0% (Figure 2A). Also of

importance, chicken muscles were able to extract the same amount of salt-soluble proteins at 1%

salt as beef muscles extracted at 2.5% salt, and that pork muscles never equaled this amount even

at 3.5% salt (Figure 2A).

Comparing salt-soluble protein content as a percentage of solids weight (weight minus

fat and moisture), the main effects of species and salt were significant (P < 0.01), however, there

was a significant interaction of species and muscle type (P < 0.01) and species and salt (P <

0.01). The interaction of species and muscle type was due to the increased salt-soluble protein

content of chicken light muscle compared to chicken dark muscle and the lack of differences

within beef and pork muscles (Figures 3A, B, C). The interaction of salt and species was due to

the differences (P < 0.05) of all species, when compared at the same salt concentration (Figure

2B). When comparing the same salt concentration, chicken muscles expressed higher contents

of salt-soluble proteins, followed by beef and finally pork (Figure 2B). Also of importance,

chicken muscles were able to extract the same content of salt-soluble proteins at 1% salt as beef

muscles at 3% salt; an amount that was not able to be extracted from pork even at 3.5% salt

(Figure 2B). Within species, chicken light muscles demonstrated increased (P < 0.02) values in

salt-soluble protein content compared to dark muscles at all salt concentrations, except 0 and

2.5% (Figure 3B). However, pork muscles were only different at 3.5% (P < 0.01)(Figure 3A),

and beef muscles were different at 1% (P < 0.02), 2.5% (P < 0.05), and 3% (P < 0.05) (Figure

18

3C). The values for salt-soluble protein content as a percentage of solids weight may be more

accurate in determining differences in the amount of protein available in these meat sources since

it is corrected for the moisture and fat content.

Identifying salt-soluble protein content of meat sources is important because these

proteins act as emulsifiers in further processed products (Hudspeth and May, 1967). In industry,

most processes included of 1.5-3.5% salt, and at these levels we demonstrate chicken as a species

will have more salt-soluble proteins than pork or beef to aid in the processing of meat products.

Also, chicken light muscles would be even more beneficial due to the advantages in

extractability over chicken dark muscles.

Conclusions

Overall, the largest quantity of salt-soluble proteins was extracted from chicken followed

by that of beef and finally pork. Chicken light muscles exhibited higher extractability at low salt

concentrations (0.5-2%) with light muscles containing more extractable salt-soluble proteins

compared to dark muscles as a percentage of solids weight. There were no differences in pork

muscles at these low salt concentrations (0.5%-2%). Beef muscles did exhibit a difference at

1%, when comparing within this low salt range (0.5%-2%), with dark muscles being greater than

light muscles. This study suggests that chicken light muscles could be used at lower salt

concentrations compared to chicken dark, or beef and pork muscles due to the increase in amount

of salt-soluble protein extracted that is needed to manufacture further processed products.

19

References

Beecher, G. R., Cassens, R. G., Hoekstra, W. G., and Briskey, E. J. (1965). Red and white fiber content and associated post-mortem properties of seven porcine muscles. Journal of Food

Science, 30, 969-976.

Boler, D. D., Holmer, S. F., Duncan, D. A., Carr, S. N., Ritter, M. J., Stites, C. R., Petry, D. B., Hinson, R. B., Allee, G. L., McKeith, F. K., Killefer, J. (2011). Fresh meat and further processing characteristics of ham muscles from finishing pigs fed ractopamine hydrochloride. Journal of Animal Science, 89, 210-220.

Gil, M., Delday, M. I., Gispert, M., i Furnols, M., Maltin, C. M., Plastow, G. S., Klont, R., Sosnicki, A. A., Carrión, D. (2008). Relationships between biochemical characteristics and meat quality of Longissimus thoracis and Semimembranosus muscles in five porcine lines. Meat Science, 80(3), 927-933.

Gleibermann, L. (1973). Blood pressure and dietary salt in human populations. Ecology of Food



Hultin, H. O., Feng, Y., and Stanley, D. W. (1995). A re-examination of muscle protein solubility. Journal of Muscle Foods, 6, 91-107.




Lee, S. H., Joo, S. T., and Ryu, Y. C. (2010). Skeletal muscle fiber type and myofibrillar proteins in relation to meat quality. Meat Science, 86, 166-170.

Leseigneur-Meynier, A., and Gandemer, G. (1991). Lipid composition of pork muscle in relation to the metabolic type of the fibres. Meat Science, 29, 229-241.


Science, 48, 994-997.


20

Novakofski, J., Park, S., Bechtel, P. J., and McKeith, F. K. (1989). Composition of Cooked Pork Chops: Effect of Removing Subcutaneous Fat Before Cooking. Journal of Food Science, 54, 15-17.

Page, L. B. (1976). Epidemiologic evidence on the etiology of human hypertension and its possible prevention. American Heart Journal, 91, 527-534.

Porter, G. A. (1983). Chronology of the sodium hypothesis and hypertension. Annals of Internal

Medicine, 98, 720-723.


Science, 49, 709-713.



Seggern, D. D. V., Calkins, C. R., Johnson, D. D., Brickler, J. E., and Gwartney, B. L. (2005). Muscle profiling: Characterizing the muscles of the beef chuck and round. Meat Science, 71, 39-51.

Tobian, L. (1997). Dietary sodium chloride and potassium have effects on the pathophysiology of hypertension in humans and animals. The American Journal of Clinical Nutrition, 65, 606S-611S.

Xiong, Y. L., Cantor, A. H., Pescatore, A. J., Blanchard, S. P., and Straw, M. L. (1993). Variations in muscle chemical composition, pH and protein extractability among eight different broiler crosses. Poultry Science, 72, 583-588.

21

Tables and Figures

Table 1. Effects of species and muscle on proximate composition and pH of raw materials

Light Dark Light Dark Light Dark SEM Species Muscle Interaction

Moisture, % 76.12 73.57 74.60 66.86 73.86 74.36 0.15 <0.01 <0.01 <0.01

Fat, % 1.79 7.08 3.58 15.87 6.34 5.71 0.19 <0.01 <0.01 <0.01

pH 5.98 6.40 5.76 6.11 5.71 5.72 0.01 <0.01 <0.01 <0.01

P - valuesChicken Beef Pork

21

22

Figure 1. Salt-soluble protein content of light and dark muscles of pork, beef and chicken (as a percentage of wet tissue weight). Within a level of salt, asterisks indicate a difference at P < 0.05 between chicken light and all other species and muscle combinations.

0

1

2

3

4

5

6

7

0 0.5 1 1.5 2 2.5 3 3.5

% W

et W

eigh

t

% Salt

Pork Dark Pork Light Beef Dark Beef Light Chicken Dark Chicken Light

Species * Muscle * Salt P = 0.01

* * *

* * * *

23

Figure 2. Salt-soluble protein content of chicken, beef, and pork (A) (as a percentage of wet tissue weight) (B) (as a percentage of solids weight basis (weight minus fat and moisture)). a, b, c

Within a level of salt, means with different letters are different at P < 0.05.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

% W

et W

eigh

t

% Salt

Chicken Beef Pork

0.00

4.13

8.25

12.38

16.50

20.63

24.75

28.88

33.00

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

% S

olid

s W

eigh

t

% Salt

Chicken Beef Pork

a a a a

b a a b b

a bb

c

b

c c

b

c c c c

a

b

a a a

b

a

b b

a a

b b b

a

c c c b

c c c c

b

a

c

A

B

Species * Salt P < 0.01

Species * Salt P < 0.01

a a

24

1

Figure 3. Salt-soluble protein content of light and dark pork muscles (A), chicken muscles (B), and beef muscles (C) (as a percentage on solids weight basis (weight minus fat and moisture)). Means lacking a common superscript are different at P < 0.05.

0.00

4.13

8.25

12.38

16.50

20.63

24.75

28.88

33.00

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

% S

olid

s W

eigh

t

% Salt

Pork Dark Pork Light

0.00

4.13

8.25

12.38

16.50

20.63

24.75

28.88

33.00

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

% S

olid

s W

eigh

t

% Salt

Chicken Dark Chicken Light

0.00

4.13

8.25

12.38

16.50

20.63

24.75

28.88

33.00

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

% S

olid

s W

eigh

t

% Salt

Beef Dark Beef Light

* * * * *

*

*

* * *

Species * Muscle P < 0.01



A

C

B

25

Chapter III

The Effects of Varying Salt Concentrations on Protein Solubility and Product

Characteristics of Bolognas Manufactured from Chicken Muscles

Abstract

This experiment evaluated product characteristics of bolognas manufactured from

pectoralis major (light) and the entire thigh (dark) muscles of chicken at various salt levels. The

study was designed as a complete randomized design in a 2x4 factorial arrangement with factors

of muscle type (light and dark) and salt concentration (0.5%, 1%, 1.5%, and 2%). Bologna was

manufactured and analyzed for salt-soluble protein content, proximate analysis, cooking yield,

pH, Minolta L*, and binding strength. Increased retention of moisture in thigh muscle bologna

contributed to improved cooked yields compared with breast muscle bolognas (P = 0.01). The

comparison of low-salt breast bologna to high-salt thigh bologna indicated a difference (P <

0.01) 0.05 percentage units extractable salt-soluble proteins as a percentage of total crude

protein, with low-salt breast exhibiting higher values. The increase in salt-soluble protein

content was reflected in higher hardness scores in low-salt breast bologna compared to high-salt

thigh bologna (P < 0.01). This study suggests that incorporating chicken light muscles into

processed products would reduce the amount of salt needed to produce products with acceptable

processing characteristics.

Introduction

Today, there is growing concern in the medical community that excess salt consumption

is leading to the development of disease. Nearly 16.7 million deaths worldwide and 685,000

U.S. deaths annually are attributed to cardiovascular disease (Mackay and Mensah, 2004; Hoyert

et al., 2006). Hypertension, a chronic, abnormally high systolic and diastolic arterial blood

26

pressure (Lopez et al., 2006) has been identified as a contributing risk factor to the development

of cardiovascular disease (JNC VI, Working Group). In 1972, Dahl described the link between

dietary sodium intake and the development of hypertension, which other researchers have further

demonstrated (Page, 1976; Porter, 1983; Gleibermann, 1973; Tobian, 1997). Therefore,

reducing sodium intake, including that in processed meats is crucial to improving human health.

The need to reduce sodium levels in food products is evident; however, the use of sodium

chloride in the further processing of meat products is essential. Salt disrupts the myofibrillar

structure within muscle and allows myofilaments to swell and solubilize (Hamm, 1961).

Increasing sodium chloride concentration increases salt-soluble protein extraction, resulting in

increased amounts of fat and water that can be bound in products (Swift and Sulzbacher, 1963).

As the amount of salt-soluble proteins acting as binding agents increases in a product, the

binding strength of that product also increases (Acton, 1972). Break strength measures the

texture profile of the cooked product and indicates ability to be handled for packaging and

slicing (Herrero et al., 2008). In chicken loaves prepared entirely from either chicken breast or

chicken thigh muscle, breast meat was superior in binding qualities when comparing break

strength (Maesso et al., 1970). The purpose of this study was to determine the processing yield

and textural properties of emulsified products manufactured from chicken breast and thigh

muscles at various low salt (0.5-2%) concentrations.

Materials and Methods

Raw Materials

Approximately 120 kg of fresh, boneless and skinless chicken breast and thigh meat was

obtained from a commercial poultry plant two days postharvest. Breast muscles were trimmed

27

to isolate pectoralis major muscles. Approximately 50 kg each of pectoralis major muscles and

entire thighs were ground separately through a half-inch plate and mixed in a Hobart mixer to

form a homogenate sample. For each muscle type, eleven (30 g) samples were collected to

determine the proximate composition. While proximate composition analysis was being

conducted, ground meat was stored in vacuumed packaged bags (4°C).

Proximate Composition

The moisture and lipid content was determined for each sample using the method

described by Novakofski et al. (1989). In preparation, all samples were trimmed of external fat

and connective tissue and homogenized using a Cuisinart Food Processor. Moisture content was

determined after samples had been placed in a drying oven at 110°C for 48h. Lipid content was

then determined after washing samples in a mixture of chloroform and methanol. Results of

proximate composition analysis reported in Table 1.

Formulation

Two muscle combinations (pectoralis major muscle and thigh composite) and four

sodium chloride concentrations (0.5%, 1%, 1.5%, and 2%) with four replicates per treatment

were formulated for a total of 32 batches of bologna. Results of the proximate composition

analyses were used to determine the appropriate fractions of raw materials for an 80:20 lean to

fat ratio (Table 3). Pork back fat trim, free of visible lean, was added to reach the defined fat

inclusion levels. Chicken was placed in a bowl chopper (Talsa, Windsor Food Machinery LTD,

Kent, England) with seasonings and 1.5 pounds of ice and was allowed to mix for two

revolutions. Pork fat trim was added and the mixture was chopped on a low blade speed for 1

minute and then on high for 1 minute. Batter was removed from the bowl chopper, and four

samples (30g) were collected for proximate analysis, pH, and salt-soluble protein analysis.

28

Bologna batter was vacuumed stuffed into 5 3/8 inch collagen casings using a Handtmann stuffer

(Model# VF 80, Biberach, Germany). After stuffing, chubs were weighed and individually

identified. Product was allowed to rest at 2°C overnight before cooking. Bologna was cooked in

an Alkar smokehouse (Lodi, Wisconsin) to an internal temperature of 66.1°C and chilled at 2°C

for 24 hr. After chilling, the bolognas were weighed to determine cook loss and then peeled

from casings. Bolognas were cut into six 2.54 cm pieces for texture analysis, proximate

composition, pH, color.


The extractability of both sarcoplasmic and myofibrillar proteins were determined using

the method described by Boler et al. (2011). A master mix extraction buffer of 0.01M 2-[N-

Morpholino]ethanesulfonic acid was used to make the following eight NaCl extraction buffers

0% (0M), 0.5% (0.09M), 1% (0.17M), 1.5% (0.26M), 2% (0.34M), 2.5% (0.43M), 3% (0.51M)

and 3.5% (0.6M) by volume. All extraction solutions were buffered to a pH of 6.0 according to

Lan et al. (1993). Ground muscle samples (0.1 g) were placed in 2.0 mL microcentrifuge tubes

with 4mm stainless steel beads and 1.5 mL extraction buffer. Samples were homogenized

(TissueLyser II, Qiagen Inc., Valencia, CA) for 1 minute. Homogenates were centrifuged

(Microfuge® 18 Microcentrifuge, Beckman Coulter Inc., Germany) at 15000 x g for 20 min at 4°

C. Supernatants were collected for each sample, diluted 10 fold, and protein content quantified

using a BCA protein assay kit (Thermo Scientific Pierce Protein Research Products, Rockford,

IL). The amount of solubilized protein was determined using a second order polynomial

equation. Data were expressed both as a percentage of wet weight and as a percentage of total

crude protein.

29

pH

Meat (5g) was placed in a 50 mL conical tube with 20 mL of deionized water and

homogenized (Model PT 10/35, Brinkmann Instruments Co., Switzerland) for 30 seconds. pH

was measured with an automatic temperature compensation epoxy body probe attached to a

bench meter (Model 917001, Model 501, Orion Research Inc., Jacksonville, Florida) that had

been calibrated with pH 4.00 and 7.00 buffers.

Binding Strength and Compression Analysis

Binding strengths of bologna slices were analyzed using a cross bar and platform

attached to a Texture Analyzer TA.HD Plus (Texture Technologies Corp., Scarsdale, NY/Stable

Microsystems, Godalming, UK) (Souza et al., 2011). The crossbar speed was 10 mm/sec and the

load cell capacity was 100 kg. The crossbar descended until the sample was fractured and the

peak force necessary to fracture the sample was recorded. Two samples were fractured and the

average peak force was reported for each bologna.

The Bourne analysis (Bourne, 1978) was used to evaluate hardness of bologna. Four

2.54 cm cores were collected from each sample and compressed on Texture Analyzer TA.HD

Plus (Texture Technologies Corp., Scarsdale, NY/Stable Microsystems, Godalming, UK). A 5.08

cm diameter plate compressed each core in two consecutive cycles to 75 percent of the samples

original height with 2 s intervals between cycles. The cross-head moved at a constant speed of 5

mm/s. A force-time curve was plotted and the peak force of the first compression was used to

determine hardness. The values for the 4 cores were averaged and reported as hardness of each

bologna.

30

Color

Objective color scores (L*) were obtained using a Minolta CR-300 at a D65 light source

and a 0° observer immediately from the cut surface of each bologna. For each sample, one

measurement was taken from each half of the slice and the average of the two values was

reported for each parameter.

Statistical Analysis

Data were analyzed as a randomized complete design in a 2x4 factorial arrangement.

The statistical model included the main effects of muscle type (light or dark) and salt (0.5%, 1%,

1.5%, and 2%) and their interaction. Differences between moisture, fat, pH, textural properties

and color were determined using MIXED procedure of SAS (SAS Inst. Inc., Cary, N.C.). Means

for moisture, fat, pH, and color were separated using the PDIFF option and adjusted using

Tukey’s W Procedure to control for experimentwise error. Salt-soluble protein content was

analyzed as repeated measures using a first order auto regressive covariate structure with sample

serving as the subject. Single degree of freedom contrast statements were used to compare low-

salt (0.5-1%) breast bologna and higher-salt (1.5-2%) thigh bologna for salt-soluble protein

content, hardness, and break strength. Differences were deemed significant at P < 0.05.

Results and Discussion

Proximate Analysis and pH

In thigh muscle bologna batches, raw moisture content was increased over breast muscle

batches (Table 3). Also, the raw fat content of thigh muscle bologna was increased (P = 0.07)

over breast muscle bologna (Table 3). The interaction of muscle and salt can be attributed to

thigh bologna at 0.5% having a higher raw fat content (P < 0.05), compared to thigh bologna at

31

1.5% (Figure 4A). However, the raw fat content of breast bologna showed no differences at any

of the salt concentrations. Differences in raw fat content between thigh and breast bolognas may

be attributed to formulation error during the addition of fat trim to chicken trim and may have

affected further characteristics.

To account for the variation in raw fat content, this parameter was used as a covariate for

cooked fat content, cooked moisture content and cooked yield.

For cooked moisture content, thigh muscle bologna was increased compared to breast

muscle bologna (P < 0.01); however, there was an interaction of salt and muscle type (P < 0.01).

This interaction was due to thigh bologna having increased (P < 0.05) cooked moisture content at

0.5% salt compared to 1.5% salt (Figure 4B). However, breast bologna showed no differences in

cooked moisture content (Figure 4B). The main effect of muscle (P < 0.01) was significant for

cooked fat content, and there was an interaction of muscle and salt (P= 0.02) (Table 4). The

interaction was due to breast bologna tending to decrease in cooked fat content with increased

salt levels while thigh bologna exhibited the opposite trend (Figure 4C). Overall, thigh bologna

had more cooked fat content compared to breast bologna at all salt concentrations (P < 0.01)

(Table 4). The increase in moisture content and fat content of thigh muscles contributed to the

improved cooked yields of thigh muscle bologna compared to breast muscle bologna. The main

effects of species and muscle were significant (P < 0.01) for cooked yield as a percentage of

product weight (Table 4). Increasing the salt concentration resulted in increased cooked yields

for both bologna muscle types, however, thigh bologna had improved (P < 0.01) cooked yields

compared to breast bologna. The findings of improved cooked yields of chicken products with

the addition of increasing salt concentrations have been observed by other researchers (Acton,

32

1972; Lan et al., 1995; Somboonpanyakul et al., 2005). However, none of these papers

compared the cooked yields of chicken breast and chicken thighs.

The main effect of muscle type was significant (P < 0.01) for raw pH (Table 3). Breast

muscle bologna had lower pH values compared to thigh muscle bologna, which was expected

due to the method of metabolism associated with each muscle type. The increase in lactate

within the breast muscles drove the pH down compared to thigh muscle and values observed

were similar to other findings (Lee et al., 2010; Xiong et al., 1993). Increased values for thigh

pH may have led to an increase in water retention in the final product. However, pH was

buffered for salt-soluble protein content analysis to a pH of 6.0.


A single degree of freedom contrast statement was used to evaluate salt-soluble protein

content of low-salt (0.5%-1%) breast bologna and high-salt (1.5-2%) thigh bologna. Comparing

the low-salt breast bologna group to the high-salt thigh bologna group a difference (P = 0.01)

was detected, in that breast bologna extracted 1.05 percentage units more salt-soluble proteins as

a percentage of wet weight compared to thigh bologna (Figure 5A). These differences persisted

when salt-soluble protein content was corrected for total protein content of bolognas. The

comparison of low-salt breast bologna to high-salt thigh bologna indicated a difference (P <

0.01) of only 0.05 percentage units extractable salt-soluble proteins as a percentage of total crude

protein, with low-salt breast exhibiting higher values (Figure 5B). The increased extractability

of breast muscle compare to thigh muscle was consistent with the findings of several researchers

(Khan, 1962; Hudspeth and May, 1967; Maurer et al., 1969; McCready and Cunningham, 1971;

Prusa and Bowers, 1984; Richardson and Jones, 1987). Overall, the increased amount of salt-

33

soluble proteins in low-salt breast muscle bologna should impact the products overall textural

properties resulting in a firmer product when compared to high-salt thigh bologna.

Binding Strength and Compression

Break strength scores were expected to increase as the amount of extractable salt-soluble

proteins increased, due to their role as a binding agent in further processed products. As the

level of salt increased, break strength scores also increased, for both breast and thigh bologna

(Figure 6A). When comparing low-salt breast bologna to high-salt thigh bologna, it took 3.30 kg

more force to break the thigh bologna (P < 0.01) (Figure 6A). Even though it low-salt breast

bologna contained a larger quantity of salt-soluble proteins compared to high-salt thigh bologna,

that did not correlate to higher values for break strength.

Bourne (1978) defined the parameter of hardness to be a measure of the first bite of a

product. The first bite of low-salt breast bologna was increased (P < .01) by 2.19 kg of force

compared to high-salt thigh bologna (Figure 6B). The increase in hardness scores agrees with

previously published results which found that salt-soluble protein content increases corresponded

to rigidity of the product (Somboonpanyakul et al., 2005; Barbut and Mittal, 1989). The

acceptability of this product by the use of a sensory panel was not tested; however, Matulis et al.

(1994) observed the acceptable hardness scores of frankfurters to be approximate six with a

standard deviation of two, which would put low-salt breast bologna within this range.

Color

For L* color scores, the main effect of salt and muscle type were significant (P < 0.01),

however, there was a significant interaction of salt and muscle type (P = 0.05). Increasing salt

concentrations resulted in a decrease in L* color scores for both breast and thigh muscle

bologna; however, at all salt concentrations breast muscle bologna was lighter compared to thigh

34

muscle bologna (Figure 7). This result was similar to other studies, which found that as the pH

of the product measured increased there was a decrease in the recorded L* value due to an

increase in the retention of surface water (Fletcher et al., 2000).

Conclusions

In thigh muscle bologna batches, raw and cooked moisture content as well as cooked fat

content was increased over breast muscle batches (P < 0.01). The increased values for thigh pH

may have led to an increase in water retention in the final product. The increase in retention of

moisture of thigh muscles contributed to the improved cooked yields of thigh muscle bologna

compared to breast muscle bologna (P = 0.01). The comparison of low-salt breast bologna to

high-salt thigh bologna indicated a difference (P < 0.01) 0.05 percentage units extractable salt-

soluble proteins as a percentage of total crude protein, with low-salt breast exhibiting higher

values. The increase in salt-soluble protein content, however, was not reflected in a higher break

strength value for low-salt breast bologna compared to high-salt thigh bologna (P < 0.01).

Although the scores recorded for hardness did show an increase in low-salt breast bologna

compared to high-salt thigh bologna (P < 0.01). Overall, textural properties did not show the

same trend for each group compared and no human analysis was used to determine if these

products would be acceptable. Furthermore, although thigh muscle bologna was improved in

cooked yields and moisture content, it was not tested if breast muscle bologna would still be

deemed acceptable by consumers. The ability of chicken to extract high amounts of salt-soluble

proteins at low salt concentrations could be taken advantage of in the meat industry by

manufacturing products that incorporate both chicken and beef or pork. This would allow for a

variety of low sodium meat products to be manufactured.

35

References

Acton, J. C. (1972). Effect of heat processing on extractability of salt-soluble protein, tissue binding strength and cooking loss in poultry meat loaves. Journal of Food Science, 37, 244-246.

Barbut, S. and Mittal, G.S. (1989). Effects of salt reduction on the rheological and gelation properties of beef, pork, and poultry meat batters. Meat Science, 26, 177-191.

Boler, D. D., Holmer, S.F., Duncan, D.A., Carr, S.N., Ritter, M.J., Stites, C.R., Petry, D.B., Hinson, R.B., Allee, G.L, McKeith, F.K., and Killefer, J. (2011). Fresh meat and further processing characteristics of ham muscles from finishing pigs fed ractopamine hydrochloride. Journal of Animal Science, 89, 210-220.

Bourne, M. C. (1978). Texture profile analysis. Food Technology, 32, 62-66.

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38

Tables and Figures

Moisture, % Fat, %Breast 74.44 3.93

Thigh 71.36 11.90

Table 2. Proximate Compostion of breast and thigh muscles

Breast Thigh SEM Muscle Salt InteractionPork Fat Trim, kg 1.13 0.63Chicken Trim, kg 5.67 6.17Raw Moisture, % 70.43 71.60 0.11 < 0.01 0.30 0.63Raw Fat, % 12.81 13.17 0.14 0.07 0.01 0.01Raw pH 5.72 6.27 0.01 < 0.01 0.23 0.58

P-valueBologna

Table 3. Formulation of chicken bologna batches

39

Breast Thigh 0.05% 1% 1.50% 2% SEM Muscle Salt Interaction

Cooked Moisture, % e

66.99 68.29 67.94a

67.98a

67.49a

67.16a

0.28 < 0.01 0.10 < 0.01

Cooked Fat, % f

14.61 15.60 15.19a

15.22a

15.22a

14.81a

0.23 < 0.01 0.38 0.02

Cook Yield, % g

91.36 92.19 89.78c

91.66b

92.64ab

93.02a

0.36 0.01 < 0.01 0.34

a, b, c Means lacking a common superscript are different P < 0.05

d pH of bologna batch after emulsification

e Moisture content of bologna after cooking

f fat content of bologna after cooking

All means were calculated using raw fat content as a covariate

P-valueMuscle

Table 4. Effect of muscle and salt on processing characteristics of bologna

Salt Concentration

g�� *100

39

40

Figure 4. Effects of muscle and salt on processing characteristics of bologna. Raw fat content (A), cooked moisture content (B), and fat content as a percentage (C). Means lacking a common superscript are different at P <0.05.

8

9

10

11

12

13

14

15

0.5 1 1.5 2

% R

aw F

at C

onte

nt

% Salt

Breast Thigh

a

abab abbb b ab

64

65

66

67

68

69

70

71

0.5 1 1.5 2

% C

ooke

d M

oist

ure

Con

tent

% Salt

Breast Thigh

aab

bcabc abccc

c

1212.5

1313.5

1414.5

1515.5

1616.5

17

0.5 1 1.5 2

% C

ooke

d Fa

t Con

tent

% Salt

Breast Thigh

bc

aab

abcabcab

bc c

A

B

C

Muscle * Salt P = 0.01

Muscle * Salt P = 0.02

Muscle * Salt P < 0.01

41

Figure 5. Salt-soluble protein content of breast and thigh as a percentage of wet weight (A) and as a percentage of total crude protein (B). Asterisks indicate differences between low-salt (0.5-1%) breast bologna and high-salt (1.5-2%) thigh bologna at P < 0.05.

0

0.5

1

1.5

2

2.5

3

3.5

4

0.5 1 1.5 2

% W

et W

eigh

t

% Salt Breast Thigh

0

4

8

12

16

20

24

0.5 1 1.5 2

% C

rude

Pro

tein

Wei

ght

% Salt Breast Thigh

B

A

Muscle P < 0.01

Muscle P < 0.01

*

*

*

*

42

Figure 6. Force required to break slices of bologna (A) and force required to compress slices of bologna made from chicken breast and thigh muscles (B). Asterisks indicate differences between low-salt (0.5-1%) breast bologna and high-salt (1.5-2%) thigh bologna at P < 0.05.

5

6

7

8

9

10

11

12

0.5 1 1.5 2

Bre

akst

reng

th (

Kg)

% Salt Breast Thigh

4.5

5.5

6.5

7.5

8.5

9.5

10.5

0.5 1 1.5 2

Har

dnes

s (K

g)

% Salt

Breast Thigh

*

*

*

*

B

A



43

Figure 7. Minolta L* values of bologna made from chicken breast and thigh meat. Asterisks indicate differences between muscle types at P < 0.05.

64

66

68

70

72

74

76

0.5 1.0 1.5 2.0

L*

valu

e

% Salt Breast Thigh

*

*

*

*

Documents

SALT CONCENTRATION AND SPECIES AFFECTS PROTEIN