Understanding the spoilage mechanism of refrigerated turbot (Scophthalmus maximus) using high-throughput sequencing combined with untargeted metabolomics

Turbot is susceptible to spoilage during cold storage; however, the interaction between spoilage microorganisms and their metabolic pathway in refrigerated turbot remains unclear. Elucidating this relationship can help provide more effective strategies for the preservation of turbot. This study explored the changes in freshness indexes of refrigerated turbot, including microbial population and chemical indicators. The microbial community and metabolites in refrigerated turbot were analyzed using 16S rRNA sequencing and untargeted metabolomics. Results showed that the freshness of refrigerated turbot declined as the storage period extended, accompanied by yellowing of the fish. Metabolomic results identified 1159 significant differential metabolites during the storage of turbot. Metabolic pathway enrichment illustrated that purine metabolism, amino acid metabolism and biosynthesis, and pentose phosphate pathways, which are involved in the degradation process of fish, were the primary spoilage mechanisms of turbot. Eight potential spoilage biomarkers were identified, among which hypoxanthine, xanthine, Tyr-Leu, Phe-Asn, Gly-L-Phe, and L-Ala-L-Trp exhibited a significantly positive relationship with Shewanella, Acinetobacter, and Brochothrix, which were the dominant spoilage organisms in refrigerated turbot. Furthermore, L-glutamine and PC(20:5(5Z,8Z,11Z,14Z,16E)) exhibited a negative relationship with the abundance of Psychrobacter. These identified biomarkers can provide precise targets for the development of preservatives for aquatic products.