Abstract: In this paper, 4D-label-free proteomics (4D-LFQ) was used to explore changes in the content of myoglobin and its transformation into derivatives in the Longissimus dorsi muscle in Qinchuan cattle during the first eight days of postmortem storage. The results showed that during storage from day 0 to day 4, the expression of the myoglobin had an upward trend, but then decreased. Totally 14 differentially expressed proteins related to myoglobin and its derivatives were identified, including metabolic enzyme, oxidoreductase, peroxidase and chaperone protein, which could together regulate the change in myoglobin content and the transformation between myoglobin and its three derivatives. Specifically, myoglobin expression showed an overall downward trend, and the relative content of oxymyoglobin continuously declined, while the relative contents of deoxymyoglobin and metmyoglobin gradually rose, resulting in browning in meat color. The results of this study will be useful for understanding the complex biochemical mechanism underlying color changes in the meat of Qinchuan cattle during storage.

Key words: meat of Qinchuan cattle; myoglobin; myoglobin derivatives; 4D-label-free proteomics; meat color