The calpain proteolytic system in different types of ovine skeletal muscles and relationship to meat tenderness

The calpain system is involved in postmortem tenderisation of meat. Muscle type also influences tenderness and aging rate. This study investigated the extent to which differences in the calpain system may account for differences in tenderness. Calpain and calpastatin activities were measured from 12 different ovine muscles. Shear force was determined on muscle aged at 15°C for 1, 2, 3 and 4 days postmortem and ultimate pH measured. Calpastatin, μand m-calpain, shear force and pH measures were different between muscles. Calpastatin activity had a positive association and both μ-calpain:calpastatin ratio and μ-calpain had a negative association with shear force of aged muscle, within muscles. These results suggest that greater calpastatin activity and less μ-calpain activity results in tougher meat. This may result from increased inhibitory actions of calpastatin on the proteolytic actions of calpain, resulting in less proteolysis of myofibrillar proteins and tougher meat.