The dynamic changes of microbial diversity and biogenic amines in different parts of bighead carp (Aristichthys nobilis) head during storage at-2 degrees C

Microorganisms are important factors in fish spoilage, causing the degradation of amino acids to form undesired biogenic amines (BAs). Thus, the composition of BAs and microorganisms in the four parts of bighead carp head and the surface mucus were evaluated in this work during storage at-2 degrees C. Seven BAs were measured in fish head samples, including tryptamine (TRY), phenethylamine (PHE), putrescine (PUT), cadaverine (CAD), tyra-mine (TYR), spermidine (SPD), and spermine (SPM). PHE, TYR and PUT were the predominant ones, whose contents in different parts of fish heads generally ascended during the storage. These samples contained microbiota comprising 202 species and a total of 41 phyla and 391 genera. As the storage proceeded, the bac-terial diversity of all samples decreased significantly. Additionally, the main phyla of Proteobacteria, Bacter-oidetes, and Firmicutes were identified, and the major genera were Shewanella, Flavobacterium, and Lactococcus. In-depth correlation analysis also found that the abundances of Streptococcus, Proteocatella and Lactococcus were positively related to the accumulation of PUT, PHE and TYR, indicating the key roles of these bacteria in the formation of BAs. These findings in the present work would provide a guideline for future investigations on the preservation and processing of fish.