Abstract: The present study explored the mechanism of the occurrence of dark cutting beef through comparing the sarcoplasmic proteomics of normal pH (5.59) and dark cutting beef (pH 6.54) at 45 min and 24 h post-mortem and analyzing the differentially expressed proteins. The results revealed that 20 differentially expressed proteins were identified. Of these proteins, 9 were metabolic enzymes, 4 were antioxidant proteins and 4 were chaperones. Compared with dark cutting beef, all energy-related enzymes (adenylate kinase 1, creatine kinase M chain, Phospholysine phosphohistidine inorganic pyrophosphate phosphatase, succinate-CoA ligase, UTP-glucose-1-phosphate uridylyltransferase, and S-adenosylhomocysteine hydrolase) except adenylate kinase 1 (which was overexpressed in dark cutting beef) at postmortem 24 h, and the glycometabolic enzymes (phosphoglucomutase 1 and myophosphorylase) were overexpressed in normal pH beef. All antioxidant proteins, and heat shock protein beta-1 and beta-2 were overexpressed in normal pH beef, while alpha-crystallin B chain was overexpressed in dark cutting beef. The development of dark cutting beef could be directly explained by lower abundances of glycometabolic enzymes and energy-related enzymes when compared to normal pH beef. Moreover, succinate-CoA ligase, heat shock protein beta-1 and alpha-crystallin could be employed as biomarkers to identify dark cutting beef.

Key words: dark cutting beef, sarcoplasmic proteomics, metabolic enzymes, antioxidant protein, chaperones