Abstract: In order to explore the mechanism of postmortem energy metabolism in Qinchuan cattle muscle during cold storage and its effect on meat quality, this study investigated the proteomic changes in the Longissimus dorsi muscle of Qinchuan cattle during different storage periods (0, 4 and 8 days) using 4D label-free quantitative (4D-LFQ) proteomics, and high performance liquid chromatography (HPLC) was used to detect the changes of energy substances. The results showed that ATP synthase subunit δ and ATP synthase subunit γ, both related to energy metabolism, were up-regulated by 1.516 (P = 0.017), and 1.579 times (P = 0.037), respectively on day 8 compared with those on day 0, NADH dehydrogenase [ubiquinone] 1β subunit 5 was down-regulated by 0.497 times (P = 0.023) on day 8 compared with that on day 4 and succinate CoA linker [ADP formation] subunit β was down-regulated by 0.762 times (P = 0.000 7) on day 8 compared with that on day 0, NADH dehydrogenase [ubiquinone] 1 α subunit 6 was up-regulated by 1.467 times (P = 0.026) on day 4 compared with that on day 0, and cytochrome c oxidase subunit 7A1 was down-regulated by 0.692 times (P = 0.024) on day 8 compared with that on day 4. The changes in the expression abundance of the above six proteins could affect the synthesis and transportation of ATP and other energy substances through mitochondrial electron transport, respiratory chain complex I assembly, ATP biosynthesis and other processes, thereby resulting in insufficient supply of energy materials in muscle cells during cold storage, and consequently affecting the change of meat quality. ATP content was reduced by 95.07% after 8 days of storage, affecting myoglobin transformation, leading to the occurrence of browning, promoting anaerobic glycolysis to produce energy and lactic acid, causing muscle acidification, and leading to cell apoptosis and finally myofibrillar protein hydrolysis to promote muscle tenderness changes.

Key words: Qinchuan cattle meat; 4D-label-free quantitative proteomics; energy metabolism; meat quality; meat color; muscle acidification; tenderness