Protein expression and oxygen consumption rate of early postmortem mitochondria relate to meat tenderness

Oxygen consumption rate (OCR) of muscle fibers from bovine semimembranosus mus- cle of 41 animals was investigated 3 to 4 h and 3 wk postmortem. Significant relations (P < 0.05) were found between OCR measurements and Warner- Bratzler shear force measurement. Muscles with high mitochondrial OCR after 3 to 4 h and low nonmi- tochondrial oxygen consumption gave more tender meat. Tender (22.92 ± 2.2 N/cm 2 ) and tough (72.98 ± 7.2 N/cm 2 ) meat samples (4 samples each), separated based on their OCR measurements, were selected for proteomic studies using mitochondria isolated approximately 2.5 h postmortem. Twenty-six differ- ently expressed proteins (P < 0.05) were identified in tender meat and 19 in tough meat. In tender meat, the more prevalent antioxidant and chaperon enzymes may reduce reactive oxygen species and prolong oxy- gen removal by the electron transport system (ETS). Glycolytic, Krebs cycle, and ETS enzymes were also more abundant in tender meat.