Post-mortem quality changes in iced Pacific shrimp (Pandalus jordani)

Graduation date: 1973The biochemical and organoleptic changes that took place in\ud raw whole Pacific shrimp and in the cooked meat during eight days\ud of iced storage were investigated.\ud A steady increase of both microbial numbers on the raw shrimp\ud and pH in the raw shrimp and cooked meat was observed.\ud The levels of total and non-protein nitrogen and total carotenoid\ud pigment decreased during the storage period. Tyrosine levels showed\ud a. decrease in the raw shrimp, but a progressive increase in the\ud cooked meat was observed. Although proteolytic and polyphenolase\ud activity in the raw shrimp decreased during storage, the losses in\ud nitrogenous components was probably related to a combination of\ud the autolytic degradation of the shrimp coupled with the washing action\ud of melting ice.\ud Trimethylamine oxide levels were shown to decrease in raw\ud shrimp daring storage due to the washing action of melting ice and\ud its reduction to dimethylamine and formaldehyde and in lower\ud amounts, to trimethylamine. The latter, probably is the result of\ud bacterial activity, while the former is due to the action of enzyme\ud systems in the shrimp. Levels of dimethylamine and formaldehyde\ud increased in a parallel manner during the storage period. Trimethylamine\ud levels also increased, but at a much slower rate.\ud Organoleptic quality as shown by taste panel evaluations progressively\ud declined during the storage period. Dimethylamine and\ud formaldehyde levels appeared to be more sensitive indices of cooked\ud shrimp quality than microbial numbers, pH and trimethylamine\ud levels