Post-mortem quality changes in iced Pacific shrimp (Pandalus jordani)
1972
Cavazos, Sergio Flores
The biochemical and organoleptic changes that took place inraw whole Pacific shrimp and in the cooked meat during eight daysof iced storage were investigated.A steady increase of both microbial numbers on the raw shrimpand pH in the raw shrimp and cooked meat was observed.The levels of total and non-protein nitrogen and total carotenoidpigment decreased during the storage period. Tyrosine levels showeda. decrease in the raw shrimp, but a progressive increase in thecooked meat was observed. Although proteolytic and polyphenolaseactivity in the raw shrimp decreased during storage, the losses innitrogenous components was probably related to a combination ofthe autolytic degradation of the shrimp coupled with the washing actionof melting ice.Trimethylamine oxide levels were shown to decrease in rawshrimp daring storage due to the washing action of melting ice andits reduction to dimethylamine and formaldehyde and in loweramounts, to trimethylamine. The latter, probably is the result ofbacterial activity, while the former is due to the action of enzymesystems in the shrimp. Levels of dimethylamine and formaldehydeincreased in a parallel manner during the storage period. Trimethylaminelevels also increased, but at a much slower rate.Organoleptic quality as shown by taste panel evaluations progressivelydeclined during the storage period. Dimethylamine andformaldehyde levels appeared to be more sensitive indices of cookedshrimp quality than microbial numbers, pH and trimethylaminelevels.
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