Physicochemical changes and comparative proteomics analysis of hairtail (Trichiurus lepturus) fish muscles during frozen storage

Hairtail (Trichiurus lepturus) muscle proteins are susceptible to oxidative denaturation during frozen storage. The aim of this study is to investigate their quality changes by physicochemical analysis and proteomics when stored at −7 °C or −23 °C. Results showed that the space between the myofibers increased and parts of myofibers degraded with extension of storage time. The increase in K value and TVB-N value suggested that the freshness of hairtails decreased with storage time. Salt-soluble protein content and SDS-PAGE analysis indicated that the lower storage temperature inhibited protein degradation. To reveal the mechanism of protein degradation, TMT-labeled quantitative proteomic analysis was performed. The structural proteins including myosin heavy chains and actin-related proteins were down-regulated during frozen storage, whereas the cathepsin D, pyruvate kinase, and proteasome were up-regulated. Storage at a higher temperature (−7 °C) accelerated the up- or down-regulation of these differentially expressed proteins. Up- or down-regulated pathways including oxidative phosphorylation, glycolysis/gluconeogenesis, the degradation of valine, leucine and isoleucine mainly accounted for the protein degradation and quality reduction for hairtails during frozen storage. These results provided a theoretical basis for improving the quality stability of hairtails during frozen storage.