Effect of Ultimate pH on Postmortem Myofibrillar Protein Degradation and Meat Quality Characteristics of Chinese Yellow Crossbreed Cattle

This paper describes the complex effects of postmortem ultimate pH (pHu) on Chinese Yellow crossbreed cattle quality during postmortem ageing and provides an explanation of how pHu affects beef tenderness. High pHu beef had the highest initial tenderness (P < 0.05) compared with other groups at 1 day postmortem. Intermediate and low pHu beef had similar initial WBSF at 1 day postmortem, but intermediate pHu beef had slower tenderization rate than low pHu beef (P < 0.05). Purge loss, cooking loss, L*, a*, and b* values decreased with increasing pHu during ageing (P < 0.05). Myofibril fragmentation index (MFI) was higher in high pHu beef than intermediate and low pHu beef throughout ageing (P < 0.05). Protein degradation studies found that desmin and troponin-T appeared degraded within 0.5 h postmortem for high and low pHu beef, compared to >2 days for intermediate pHu beef. Overall, Chinese Yellow crossbred cattle tenderness is related to pHu, which may be affected by proteolytic enzymatic activity. Therefore, pHu may be used to predict beef tenderness and other quality characteristics during postmortem ageing. To achieve consistent tenderness, different ageing times should be used, depending on pHu.