Deteriorative reactions of Pacific whiteleg shrimp (Litopenaeus vannamei) during chilled storage: enzymatic degradation, microbial activity, and quality changes

Abstract

Pacific whiteleg shrimp (Litopenaeus vannamei) is one of the signature aquatic products in the city of Zhuhai and the Greater Bay area of southern China. Due to its high perishability under ambient conditions, the deterioration during storage can result in the decline of eating quality and nutrient loss. This study investigated the deteriorative mechanisms of Pacific whiteleg shrimp during 7-day storage at 4 °C, especially on enzymatic autolysis, oxidative reactions, and microbial growth. Comparing with fresh shrimp, on day 7, significant higher pH (7.70), total volatile basic nitrogen content (81.32 mg/100 g), and peroxide value (17.09 mg hydroperoxide/kg) were found (p < 0.05), demonstrating the accumulation of alkaline amine metabolites and higher degree of lipid oxidation. Shrimp protein degradation was revealed by the increase of peptides, loss of sulfhydryl groups, as well as activity decline of endogenous enzymes. Vibrio, Photobacterium, Fusibacter, Pseudomonas, Ralstonia and Shewanella were identified as the predominant bacterial strains in fresh shrimp samples, while lactic acid bacteria were found to enumerate substantially during shrimp deterioration. Pearson's correlation analysis was performed in this study, and significant strong correlations were found between the chemical degradative reactions and microbial growth, as well as the shrimp textural changes. The deteriorative mechanisms of Pacific whiteleg shrimp explored in this study can serve as the fundamental knowledge for developing advanced seafood preservation techniques or active packaging materials in the future.