Inactivity of μ‐Calpain Throughout Postmortem Aging of Meat

ABSTRACT: In order to determine the involvement of μ‐calpain in the tenderization of meat during postmortem aging, μ‐calpain was prepared from porcine skeletal muscle and its activity was measured under various conditions, using casein and myofibrils as the substrate. μ‐Calpain was inactive at pH 5.89 and below 15 °C. Even when the reaction time was extended to 10 h, it was entirely inactive at pH 5.62 and 5 °C. In the early postmortem stage, when the pH value of muscle is above 6.0, μ‐calpain was considered to be inactive due to the low concentration of sarcoplasmic calcium ions. μ‐Calpain is, therefore, irrelevant to the tenderization of meat throughout postmortem aging.