QUALITY ASSESSMENT OF FARMED BLACK TIGER SHRIMP (PENAEUS MONODON) IN SUPPLY CHAIN: ORGANOLEPTIC EVALUATION

QUALITY ASSESSMENT OF FARMED BLACK TIGERSHRIMP (PENAEUS MONODON) IN SUPPLY CHAIN:

ORGANOLEPTIC EVALUATION

KHAIRUL AZAM1, S.M. NAZMUL ALAM2,3 and SHAM SUN NAHER1

1Fisheries and Marine Resource Technology DisciplineKhulna University

Khulna, Bangladesh

2School of Social Sciences and Asian LanguagesFaculty of Humanities

Curtin University of TechnologyGPO Box U1987

Perth, Western Australia 6845, Australia

Accepted for Publication July 25, 2008

ABSTRACT

Organoleptic quality of the farmed shrimp (Penaeus monodon) through-out the supply chain was investigated under two conditions – normal practicesusing no ice and under experimental conditions using ice at the ratio of 1:1(ice : shrimp). Overall, organoleptic acceptability score ranged betweenhighly acceptable and moderately acceptable (shrimp farm = 8.8, depot =5.47, commission agent = 6.67 and processing plant = 6.33 in a scale of 10)for shrimp under normal practices and a relatively better score and quality ofshrimp under experimental conditions as judged by the organoleptic evalua-tion. The overall organoleptic score between the two experiments did not differsignificantly (P � 0.05).

PRACTICAL APPLICATIONS

From the moment the shrimp is caught, the deterioration process startsand its quality is affected. The most frequent problem is temperature fluctua-tion in raw materials due to (1) mishandling after harvest, (2) lengthy trans-portation times to processing plants or (3) manual processing where shrimp arekept for several hours waiting under each stakeholder supply chain. Theseresult in uncertainty of the shelf life and lower quality products. A score sheet

3 Corresponding author. TEL: +61-8-9266-4306; FAX: + 61-8-9266-3166; EMAIL: [email protected]

Journal of Food Processing and Preservation 34 (2010) 164–175.164 DOI: 10.1111/j.1745-4549.2008.00331.x

© 2009 The Author(s)Journal compilation © 2009 Wiley Periodicals, Inc.

is prepared based on well-defined characteristic changes (appearance, flavor,odor and texture) that occur in the deteriorative process of shrimp. Demeritpoints are assigned to attributes and the resulting scores prescribe overallacceptable quality. Considering food safety, organoleptic evaluation is one ofthe most often used simple methods for assessing freshness and quality in thefish and shrimp inspection services, and routinely applicable on all levels ofmarketing from harvesting to the processing plants.

INTRODUCTION

Food quality refers to the wholesomeness or the state of excellence of aparticular product in terms of its appearance, shape, color, taste and competi-tiveness in price to the buyer. At present, importing countries are becomingmore conscious of quality as a characteristic of the end product and of theprocess by which the product is produced, and are imposing stringent qualitystandards for imported products.

In the seafood literature, a key aspect of quality is freshness and con-siderable effort has gone into evaluating various tests as indicators of fresh-ness (Olafsdottir et al. 1997). The freshness of a particular food refers to itsdegree of excellence as measured by all sensory/organoleptic variables suchas appearance, texture, odor and flavor. In seafood products, freshness is themost important criterion for judging quality (Botta 1994, 1995). The locationof harvest (Huss 1988), time of year (Love 1988), method of catching andproduction (Botta et al. 1987; Huss 1988), and the manner in whichseafood is handled (Botta et al. 1989) seriously affect a product’s degree ofexcellence.

Quality of shrimp is usually dependent on species and storage tempera-ture (0, 10, 20 and 30C), although researchers have focused on temperature asthe main determinant of quality. Higher storage temperature results in quickerspoilage (Nguyen 1997) and reduces shelf life (Matches 1982). The mostimportant means of preserving fresh shrimp is by chilling to about 0–4C. Themost common chilling media are wet ice, a mixture of ice and seawater orrefrigerated seawater (Sikorski and Sun Pan 1994). There are several studies ofthe storage stability of shrimp in ice (Fatima et al. 1981; Shamshad et al. 1990;Yamagata and Low 1995). Reilly et al. (1984) reported that the storage life forPenaeus monodon reduced by approximately 1 day for every hour delay inicing. In Bangladesh, shrimp are transported from harvesting to processingplant with or without ice and there is great variation in the usage of ice toshrimp, usually 1:0.5, 1:1 and 1:2 (Azam 2004).

Many methods are used for assessing quality and include organoleptic(Shewan and Ehrenberg 1977), total volatile base-nitrogen (Botta et al. 1984),

165BLACK TIGER SHRIMP QUALITY ASSESSMENT

and trimethylamine (Fatima et al. 1981). Of these, the sensory/organolepticevaluation is the most satisfactory and acceptable method in fish-inspectionservices in assessing the freshness and quality of fish and shellfish (Howgate1982; Larmond 1986; Connell 1995; Hyldig and Peterson 2004). The organo-leptic method offers immediate measurement of perceived attributes and pro-vides information that may be of help in better understanding consumerresponses (Hyldig and Peterson 2004). The organoleptic assessment is per-formed by using the structured scaling method known as Quality IndexMethod (QIM). In QIM, a number of important attributes such as appearance,gill color and odour, firmness, etc., are measured on a limited scale and thescores are summed to provide an index (Bremner et al. 1987). QIM can beused to predict the remaining shelf life when fish is stored in ice.

The organoleptic method may be influenced by the physiological andpsychological state of the judges. Considerable variations are often observedin the sensitivity and the test of the judges of the panel at different times andthe different circumstances under which the examinations are performed(Reay and Shewan 1949; Farber 1965).

In Bangladesh, the shrimp supply chain involves several intermediariesfrom grower to exporter. Shrimp are collected at the farm gate by small tradersor forias (1st tier of the supply chain) who sell to the nearest small depot (2ndtier). The small depot owners then sell on to large depots (3rd tier). A minorityof farmers deals directly with both small and large depots and sometimesauctions their shrimp at the spot market. The depots supply shrimp to theprocessing plants through commission agents (4th tier). The processing plants(5th tier) process the shrimp according to buyer requirements, a processmediated by a buying agent (6th tier) who also plays an important role in thedistribution channel. There exists other arrangements involving more interme-diaries in the supply chain depending on the season, transport, time and thedistance between the production area and the processing plants. Some of theintermediaries have fixed premises with preprocessing facilities and the depotsare required to meet compliance standards set by the Department of Fisheriesin accordance with the specifications of the importing countries.

The depots purchase shrimp from either the shrimp farmers or from smalltraders. The depot is a licensed premise where shrimp are brought for washing,sorting, icing and further forwarding either to the commission agent or to theprocessing plants. The commission agents are also licensed buyers with fixedpremises and operate between the depot owners and the processors. Theyprovide short-term storage facilities, and grade and sort the shrimp accordingto market demand. They give advances to depot holders on the condition thatthey sell to or through them. There are no direct links between the shrimpgrowers and the processors. This long supply chain coupled with temperaturefluctuation, inadequate icing, ineffective transport facilities and poor infra-

166 K. AZAM, S.M. NAZMUL ALAM and S.S. NAHER

structure can lead to deterioration in shrimp quality. The study was undertakento examine the organoleptic quality of farmed black tiger shrimp under normalpractice (NP) and experimental conditions (ECs).

MATERIALS AND METHODS

Study Area

The study area is located in southwestern Bangladesh where over 80% ofshrimp (P. monodon) are grown using extensive methods. The main stakehold-ers chosen for the study are shrimp farmers, depot owners, commission agentsand processing plants in the same region who hold fixed premises for growing,sorting and processing. The study drew its sample from following the shrimpmovement route from farm to processing plant. The shrimp farm is located inSoladana union of Paikgacha upazila and the depot is located in the Paikgachaupazila. The commission agent and the processing plant are located in NatunBazar area in Khulna district. The research was carried out from April toAugust 2004.

Sampling

Twenty shrimp (P. monodon) weighing between 75 and 150 g each werecollected in a bamboo basket as per NP from the shrimp farm during harvest-ing. Five shrimp were separated and packed in polythene sheets and placed inthe bamboo basket with the other 15 shrimp. The bamboo basket was thencarried by van to the depot. Here, 15 shrimp (excluding the shrimp placed inpolythene bag) were taken out and pre-processed (de-heading, grading andwashing). Ice was applied in the ratio of approximately 1:1 of shrimp to ice.The processed shrimp were packed in three separate polythene bags containingfive shrimp each and placed in an insulated box. The insulated box and thebamboo basket were then transported to the commission agent in Natun bazar,Khulna. Shrimp from the insulated box were taken out, weighed, washed andthen placed back in the polythene bag, which were stored in the insulated box.Fifteen shrimp in the insulated box and five shrimp in the bamboo basket werethen transported to the processing plant. Here, all shrimp were washed andweighed and the bamboo basket and insulated box were brought to the qualitycontrol laboratory of the Fisheries and Marine Resource Technology (FMRT)Discipline, Khulna University, Bangladesh, for analysis. Samples were drawnin triplicate at each supply chain. This method of collection of shrimp wasreferred to as NP. The average time taken to transport shrimp from harvesting(shrimp farm) to the processing plant was between 10 and 12 h. The organo-leptic quality of shrimp in the laboratory was then analyzed.


Organoleptic Evaluation

An organoleptic score sheet was developed for shrimp using the scoresheet reported by Shewan and Ehrenberg (1977) for finfish (Appendix 1).Shrimp were taken out from each stages of the supply chain and were evalu-ated using the score sheet by a panel of three experienced members of theFisheries and Marine Resource Technology Discipline of Khulna University,Bangladesh. Five parameters were rated with scores given in decreasing orderscale, i.e., odor (10 = fresh odor, 0 = extremely off odor), carapace texture(10 = hard, 0 = very soft), shell color (10 = bluish white, 0 = reddish), cara-pace color (10 = yellowish, 0 = darkened) and eye (10 = bright, 0 = opaque).From the developed organoleptic score sheet, an overall acceptability ranking(Table 1) was done.

Statistical Analysis

Analysis of variance was performed to examine whether any significantdifferences existed among the different points in the shrimp supply chain (NPand EC) using the 5% significance level.

RESULTS

The quality of shrimp at various points of supply chain as measured underNP and EC, and is illustrated in Figs. 1 and 2, respectively. The data show thatthat shrimp collected at each point were of good quality. The mean value atshrimp farm, depot, commission agent and processing plant under NP indi-cated overall good quality shrimp. Shrimp collected from the shrimp farmwere of very good quality (8.8 score: highly acceptable), which dropped

TABLE 1.OVERALL ACCEPTABILITY CHARACTERISTICS OF

SHRIMP QUALITY

Overall acceptabilitycharacteristics

Score range

Highly acceptable 8.5–10.0Acceptable 6.5–8.0Moderately acceptable 4.5–6.4Just acceptable 3.6–4.5Just unacceptable 2.6–3.5Unacceptable 1.5–2.5More than unacceptable 0.5–1.4


0

2

4

6

8

10

12

Odor Carapacecolor

Carapacetexture

Eye Shell color Mean value

Sco

re

Shrimp farm Depot Commission agent Processing plant

FIG. 1. ORGANOLEPTIC SCORES OF SHRIMP IN SUPPLY CHAIN(NORMAL PRACTICE : WITHOUT ICE)

0

2

4

6

8

10

12

Odor Carapacecolor

Carapacetexture

Eye Shell color Mean value

Sco

re


FIG. 2. ORGANOLEPTIC SCORES OF SHRIMP IN SUPPLY CHAIN(EXPERIMENTAL CONDITION : WITH ICE)


abruptly to 5.47 (moderately acceptable) at the depot, increased slightly to6.67 (acceptable) at the commission agency, and then further decreased at theprocessing plant (6.33: moderately acceptable). A significant statistical differ-ence (P � 0.05) was observed among the different points of supply chain onthe overall quality of shrimp in NP.

Turning to shrimp quality under ECs (Fig. 2), it was found that the qualityof shrimp was highly acceptable when collected at shrimp farm (8.87 score)and moderately acceptable at the point of the commission agent (7.47). Thisdecreased slightly at the processing plant. A lower acceptable score wasobserved at the depot (6.6). However, overall a better quality score wasrecorded for shrimp collected under ECs. In addition, a statistically significantdifference (P � 0.05) was recorded at the different points of supply chain.

The organoleptic quality of shrimp observed in NP and EC is comparedin Fig. 3. Under both conditions, the overall organoleptic score of shrimp didnot differ much at the shrimp farm level.

The overall organoleptic score at the shrimp farm under both conditionswas almost the same (8.80-NP; 8.87-EC). However, shrimp collected from thedepot showed a relatively better score in the controlled study (6.67 score). Thiswas repeated at commission agent and processing plant levels. There was nostatistical significance in the overall organoleptic score under both conditions.

8.8

5.47

6.67 6.33

8.7

6.677.47

7.13

0

2

4

6

8

10


Sco

re

Normal Practice Experimental Condition

FIG. 3. COMPARISON OF OVERALL ORGANOLEPTIC SCORE BETWEENTWO EXPERIMENTS

Normal practice = without ice; experimental condition = with ice.


The calculated value “t” at each point of shrimp farm, depot, commissionagent, processing plant is 0.25, 4.12, 2.96 and 1.19 while the tabulated value“t” is 2.13.

DISCUSSION

The organoleptic quality characteristics of shrimp under NP and ECindicated almost similar results at each point of the supply chain. At the shrimpfarm level, shrimp had a fresh odor, carapace color was moderately greenishwith hard texture and eyes were bright and transparent under both conditions.These attributes deteriorated as shrimp moved along the supply chain to theprocessing plant. The overall acceptability scores of shrimp in shrimp farm,depot, commission agent and processing plant were 8.8, 5.47, 6.67 and 6.33,respectively, in the case of NP. However, the EC showed better scores atshrimp farm (8.87), depot (6.67), commission agent (7.47) and processingplant (7.13) levels.

The storage quality of shrimp at different temperature has been studied(Matches 1982; Surendran et al. 1985) and the most prevalent method ofpreserving fresh shrimp is by using ice. The present study showed a betterorganoleptic score for shrimp in the EC (using ice) compared to NP.

Jayaweera and Subasinghe (1990) judged the raw appearance of shrimpand classified them as Grade I on the 1st and 3rd days of shrimp stored in iceand Grade II for shrimp stored on the 7th day. Shrimp were just acceptable onthe 10th day, after which they were rejected. In the present study, the sample-handling period took between 10 and 12 h in the distribution channel. At theshrimp farm level, shrimp quality was the best and decreased as shrimp weretransported along the supply chain to the processing plant.

Cann (1974) reported that shrimp in ice started to lose flavor in 2–4 daysand black spots were formed by 6–9 days, which affected the organolepticquality. Nguyen (1997) reported that there was a gradual loss in quality ofshrimp stored at four different temperatures (0, 10, 20 and 30C); the highestspoilage rate was observed in shrimp stored at 30C and the rate decreasedwhen temperature was lowered from 30C to 0C.

Reilly and Dangla (1986) observed that shrimp lost their value as primequality head-on products after 2 days during storage at 0C. Reilly et al. (1985)found that shrimp iced immediately kept for 17 days, while 4, 8 and 12 hdelayed iced shrimp kept for 16, 13 and 11 days, respectively. Reilly et al.(1985) reported that prawn (P. monodon) held at normal temperature wasrejected after 16 h due to discoloration with a pinkish cooked appearance,strong ammoniac odor and very soft textures. Shrimp lost up to 15% of theirbody weight after 16 h. However, in the present study, no rejection character-


istics were found in relation to eye, odor, shell color, carapace texture andcarapace color at different points of the supply chain.

Shamshad et al. (1990) reported that the shelf life of shrimp Penaeussemisulcatus caught in Nhatrang, Vietnam, was longer than that of Penaeusmerguiensis caught in Pakistan (13 days, 4 days, 25 h and 13 h when stored at0, 10, 20 and 30C, respectively). Yamagata and Low (1995) found that the shelflife of Penaeus merguiensis caught in Singapore and stored in ice was 4 days,compared to 6 days for the shrimp stored at -3C and 9 weeks stored at -10C.

CONCLUSION

Shrimp losses are mainly a result of spoilage, caused principally by lackof chilling, coupled with poor storage, distribution and marketing facilities.The spoilage process in shrimp result in changes related to flavor, texture,appearance and many biochemical components of shrimp muscle. Spoilage isirreversible and process does not improve the quality of bad raw materials.Proper icing can only preserve the state of the raw shrimp.

ACKNOWLEDGMENTS

The authors are thankful to the FMRT discipline authority of KhulnaUniversity, Bangladesh for providing lab facilities.

APPENDIX 1

Organoleptic Characters and Score Sheet for ShrimpQuality Assessment

Characters Score Characters Score

Odor Carapace colorFresh odor 10 Yellowish (fresh) 10Slight spoilage odor 7 Slightly yellowish 7Spoilage odor 5 Slightly darken 5Moderately off odor 3 Moderately darken 3Extremely off odor 0 Darken 0

Carapace texture EyeHard 10 Bright and transparent 10Slightly soft 7 Slightly dull 7Moderately soft 5 Moderately dull 5Soft 3 Dull and opaque 3Very soft 0 Fully dull and opaque 0


APPENDIX 1Continued

Characters Score Characters Score

Shell color GillBluish white (no spots) 10 Transparent 10Slight loss of brightness 7 Slightly dull 7Loss of brightness and opaque 5 Dull and opaque 5Slightly reddish 3 Soft 3Reddish (spotted) 0 Darkened 0

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QUALITY ASSESSMENT OF FARMED BLACK TIGER SHRIMP (PENAEUS MONODON) IN SUPPLY CHAIN: ORGANOLEPTIC EVALUATION