Textural and biochemical composition of penaeid shrimp at various stages of the molt cycle

Vita.Live shrimp were kept in aquaria under laboratory control environment. Each shrimp was allowed to go through one complete molt cycle to detect the length of the total molt cycle period of each individual. The molt cycle of penaeid shrimp (7-11 cm total length from rostrum to telson) was found to have a duration of approximately 16 days. Shrimp were sampled at the following molt stages: postmolt (7% of the time required to complete the previous molt), intermolt (50% of the time required to complete the previous molt), and premolt (95% of the time required to complete the previous molt). The SDS-polyacrylamide gel electrophoresis patterns of shrimp myofibrillar proteins from tail muscles at three different molt stages were evaluated. The results showed no changes in gel pattern nor relative concentration of each protein component during the molt cycle. However, gel patterns from shrimp muscles were somewhat different from beef muscles, particularly the troponin components and some other minor bands. Amino acid analyses of shrimp collagens were performed. Shrimp collagen exhibits a hydroxyproline content of 2.7%; glysine content of 29.6% and hydroxylysine content of 1.8%. The SDS-polyacrylamide gel electrophoresis patterns of shrimp intramuscular collagen from tail muscle at postmolt, intermolt and premolt were evaluated. The same gel patterns showing 3 α-chains of molecular weight 99,000, 106,000 and 116,000; and 3 β-subunits of molecular weight 158,000, 172,000 and 202,000 were found in all molt stages. However, there were differences in the concentration of band 1 (low molecular weight peptides), band 3 (α-chains; M.W. 106,000) and band 5 (β-subunit; M.W. 158,000) of intermolt shrimp when compared to premolt and postmolt. ..