Protein denaturing conditions in beef deep semimembranosus muscle results in limited μ-calpain activation and protein degradation.

The objective was to determine the effect of muscle location on protein solubility and protein degradation in deep (DSM) and superficial (SSM) portion of beef semimembranosus. At 24 h postmortem, the semimembranosus was removed from beef carcasses (n=10), packaged in high-oxygen modified atmosphere (80% O2+20% CO2), and displayed for 7 d at 1°C. DSM had higher (P<0.05) L*, a*, b*, and hue values than SSM throughout display. DSM had significantly higher protein denaturation and less protein concentration than SSM. Western blotting for μ-calpain autolysis revealed that DSM maintained more (P<0.05) unautolyzed μ-calpain than SSM. This result coincided with less desmin and troponin-T degradation in samples from the DSM. These results confirm the hypothesis that increased protein denaturation in DSM results in minimal proteolysis by negatively affecting μ-calpain activation. This demonstrates a potential to alter progression of proteolysis and improvement in tenderness associated with postmortem storage.