Abstract: In order to uncover the growth and decline of microorganisms during the processing of frozen cooked crayfish and to determine the critical control points, the traditional microbial culture method combined with high-throughput sequencing was used to analyze the changes in the microbial community at different processing stages, namely, raw materials, sand spitting, washing, cooking and finished products. The results showed that the sand spitting process could significantly reduce the number of microbes in the gills by 98.9%, but did not change the number of microbes in the intestine. The total number of colonies in the gills and intestines of crayfish decreased by 4.22 and 4.64 (lg(CFU/g)), respectively during the cooking process. The microbial load in crayfish meat was below the detection limit. Besides, the coliform bacteria and Pseudomonas were killed completely. The high-throughput sequencing results showed that the species abundance and diversity in the gills and intestine of raw crayfish were lower than those in cooked crayfish meat. The microbial community in the crayfish gills was dominated by Proteobacteria, while that in the intestine was dominated by Firmicutes. The species abundance and diversity of crayfish were reduced during sand spitting, and the relative abundance of Proteobacteria in the crayfish intestine was decreased significantly. The relative abundance of Flavobacterium in the meat and gills of crayfish was more significantly decreased after cooking compared with washing. The key control points of microorganisms during the processing of frozen cooked crayfish were determined as sand spitting and cooking, which will provide a theoretical basis for improving the quality and safety of and preserving crayfish products.

Key words: crayfish (Procambarus clarkii); frozen cooked food; microbial growth and decline; high-throughput sequencing; critical control point