Evaluation of Food Safety Risk of Frozen Cooked Crayfish Based on Microbial-Related Indicators

Crayfish (Procambarus clarkii) is nutritious and delicious, but its safety always worries consumers. This study aimed to investigate the microbial safety of frozen cooked crayfish. The total volatile basic nitrogen (TVB-N) content and pH of crayfish samples were measured to determine the end point of the shelf life. The structure and diversity of the microbial communities in the viscera and gills, muscle and shell of crayfish and the marinade were analyzed by high-throughput sequencing. The results showed that during the frozen storage of cooked crayfish, the pH of the viscera, gills and muscle decreased slowly, while the pH of the marinade and the shell increased first and then decreased. The TVB-N contents of all four samples showed an upward trend. On the 180th day, the TVB-N values of the muscle as well as the viscera and gills were 32.42 and 31.26 mg/100 g, respectively, which were higher than the accepted upper limit. The results of high-throughput sequencing showed that there were differences in the bacterial community structure of the four crayfish samples at the end of the shelf life. The decreasing order of the abundance of bacteria in these samples were marinade > viscera and gills > shell > muscle. The dominant bacterial genera in these samples were also different; Lactobacillus was dominant in the marinade. Psychrobacter and Vibrio were dominant in the viscera and gills, the dominant bacteria in the shell were Vibrio, Lactobacillus and Psychrobacter, and the dominant bacteria in the muscle were Psychrobacter and Acinetobacter. In conclusion, the microbial safety risk of the marinade and the viscera and gills in frozen cooked crayfish products was relatively high and could be reduced by combined use of various cleaning methods, adjusting the acidity of the marinade and using antibacterial agents.