CHANGES IN AMINO ACID COMPOSITION IN PASTEURIZED BLUE SWIMMING CRAB (PORTUNUS PELAGICUS) DURING CHILLED STORAGE
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Date
2014-11-22
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Fisheries College and Research Institute, Thoothukudi, Tamil Nadu Fisheries University
Abstract
Changes in the nutritional quality of edible meats of blue swimming crab (Portunus pelagicus) at various stages of processing (raw, precooked and pasteurized) and subsequent chilled storage (2oC) for three months were examined. Raw crabs were subjected to steam cooking (25 min) followed by air cooling (45 min). Cooked crabs were debacked and different types of meats viz. special, jumbo and claw meats were picked and pasteurized in a local seafood processing plant and stored in chilled storage (2oC). Samples were subjected to the analysis of proximate composition (moisture, protein, fat, carbohydrate and ash), amino acid composition, protein fractions, biochemical (TMA-N, TVB-N, TBA and Sulfhydryl content), microbiological (total plate count, anaerobic bacterial count and spore former count) and sensory qualities.
Moisture, protein, fat, carbohydrate and ash contents ranged from 79.50 to 82.06%, 13.42 to 17.78%, 0.17 to 0.31%, 0.40 to 0.49% and 1.63 to 2.24%, respectively in the raw crab meats. Significant differences (P>0.05) were observed between raw, cooked and pasteurized crab meats with respect to moisture, protein, fat, carbohydrate and ash contents. TMA, TVBN, and TBA values increased during storage, however, their values did not exceed the standard limits. Sulfhydryl contents decreased in cooked and pasteurized meats. All the ATPase activities (Ca2+ ATPase, Mg2+ ATPase and EDTA- ATPase) were very much higher in raw crab meats compared to processed meats.
Among the protein fractions, water soluble proteins were high in raw claw meat (26.20%) followed by special (23.94%) and jumbo meat (23.51%). Salt soluble proteins were high in raw jumbo meat (51.55%) and alkali soluble proteins in raw special meat (21.20%). Raw special meat contained the highest acid soluble protein fraction (3.73%) followed by jumbo (3.43%) and claw meat (3.36%). After thermal processing (cooking and pasteurization), the major loss of water soluble protein was noticed in special meat (86%) and salt soluble protein in the jumbo meat (50.32%). Alkali soluble protein increased during pasteurization, with claw meat having the highest value.
Initially, the raw crab meat had total plate count, spore former count and anaerobic bacterial count ranging from 1.9 × 14 to 3.0 × 104 cfu/g, 3.0× 102 to 6.0 × 102 cfu/g and 130 to 240 MPN/g, respectively, which decreased significantly upon thermal processing (cooking and pasteurization).
Amino acid analysis by HPLC revealed the presence of 17 amino acids in all the meat types. Glutamic acid was the predominant amino acid (13.65 – 15.20 mg/g) in all the type meats of raw crab. Thermal processing (cooking and pasteurization) reduced the essential amino acids viz. histidine, lysine and methionine and the non-essential amino acids viz. aspartic acid, glutamic acid and serine in all types of meats. During pasteurization process, major loss of essential amino acids was noticed in claw meat (41%) than that of other type of meats. Significant (P<0.05) reduction was observed in total essential amino acids of cooked and pasteurized special and claw meats. However, the overall nutritional quality of claw meat was inferior than those of jumbo and special meats. Among the soluble proteins, maximum reduction of essential amino acids was observed in acid soluble protein (35%) compared to other soluble proteins fractions.
The major loss of EAA was noticed in claw meat (41%) followed by special meat (16%) and jumbo meat (10%). This study revealed that the pasteurization process adopted in the present work significantly (P<0.05) affected the essential amino acid (EAA) contents.
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