Effects of gamma irradiation on chemical, microbial quality and shelf life of shrimp

In the present study the combined effect of gamma irradiation (1, 3 and 5 kGy) and storage at two temperatures: refrigeration (+4 degrees C) and frozen (-18 degrees C), on the shelf-life extension of fresh shrimp meat was investigated. The study was based on microbiological and physicochemical changes occuring in the shrimp samples. Total volatile base nitrogen values and trimethylamine values for irradiated shrimp samples were significantly lower than non-irradiated samples at both storage temperatures, and the rate of decrease was more pronounced in samples irradiated at the higher dose (p < 0.05). Thiobarbituric acid values for irradiated shrimp samples were significantly higher than non-irradiated samples at both storage temperatures (p < 0.05). pH values of shrimp samples were affected significantly by both irradiating dose and storage temperatures (p < 0.05). Microbial counts for non-irradiated shrimp samples were higher than the respective irradiated samples at both storage temperatures (p < 0.05). The results revealed that irradiation at high dose (5 kGy) might enhance lipid oxidation, although the growth of microorganisms and protein oxidation was inhibited. (C) 2012 Elsevier Ltd. All rights reserved.