Quality deterioration induced by microbial community in Litopenaeus vannamei during superchilling storage were demonstrated in this study. In this study, 6 microorganisms were identified as the biomarkers by 16S rDNA sequencing and 71 differential metabolites were identified by untargeted metabolomics. The correlation analysis between microorganisms and differential metabolites revealed that Oceanicaulis, Aliihoeflea, Prauserella, Chelativorans and Pseudoalteromonas had the potential to be the important microorganisms of deterioration of superchilled shrimp. Moreover, the spearman correlation analysis revealed that L* value had highly significant correlation with Shewanella (P < 0.01), and TBA value, TVC value total sulfhydryl content, TCA-soluble peptide and Ca²⁺-ATPase activity showed significantly correlation with Oceanicaulis, Prauserella, Chelativorans, Aliihoeflea and Pseudoalteromonas (P < 0.05). This study offers a better understanding for mechanisms behind quality degradation induced by microorganisms, which may help the quality maintaining of Pacific white shrimp during superchilling storage.

Proteins play a substantial role in the deterioration of partial freezing shrimp product quality. In this study, traditional protein indicators were used to determine changes in shrimp muscle quality during storage, and the changed proteins were identified using proteomic analysis. The decrease in total sulfhydryl (SH) content and the increase in carbonyl content indicate protein is denatured. The decrease in Ca²⁺-ATPase activity and the increase in surface hydrophobicity also indicate protein denatured. The increase of hydrophobic interaction and disulfide bonds suggest a larger and closer network among proteins. A total of eight changed protein bands were detected on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) diagram under partial freezing storage. Three of them were identified as α-actinin (97 kDa), invertebrate connectin (I-connectin (55 kDa)), and troponin I (30 kDa), respectively, which are essential components of myofibrillar protein. The results of the bioinformatic analysis showed that α-actinin and troponin I are unstable proteins with a secondary structure dominated by α-helix, while I-connectin is a stable protein with a secondary structure dominated by random coil. All three proteins are hydrophilic and predicted to be non-toxic on ToxinPreds.