Protein degradation of black carp (Mylopharyngodon piceus) muscle during cold storage

•Black carp muscle was stored at 4, −0.5, −3 and −20 °C.•Z-disk associate protein α-actinin was degraded at 4 °C.•Inter-myofiber and inter-myofibril gaps increased at 4 and −0.5 °C.•Extractable caseinolytic and gelatinolytic proteases decreased at 4 and −0.5 °C. This study investigated the effects of cold storage at different temperatures (4, −0.5, −3, and −20 °C) on protein degradation and its relationship to structural changes of black carp muscle. At −0.5 and 4 °C, major structural changes occurred, including the formation of gaps between myofibers and myofibrils, breakage of myofibrils and myofibers, and degradation of sarcoplasmic reticulum. Gel-based proteomic analysis showed that these structural changes were accompanied by degradation of a series of myofibrillar proteins, including titin, nebulin, troponin, myosin, myomesin, myosin-binding protein, and α-actinin. Loss of extractable gelatinolytic and caseinolytic protease activities was also observed. At −3 and −20 °C, formation of ice crystals was the most noticeable change. The major proteins were degraded at different locations in the black carp muscle, and gelatinolytic and caseinolytic proteases appear to contribute to the degradation of those proteins.