Effect of ion fluid injection on beef tenderness in association with calpain activity.

Sodium pyrophosphate plus sodium chloride (PPi) was injected into pre-rigor, hot boned biceps femoris (BF) and semimembranosus (SM) muscle from 12 heifer carcasses. The PPi injection caused higher pH values between 10 and 48 h post-mortem than found in the controls for both muscles (P<0.05). PPi injection resulted in faster decreases in the activities of μ-calpain and calpastatin than in the control for both muscles with time post-mortem (P<0.05). There were significant differences between treatments in both the BF and SM (P<0.05). There was evidence that PPi-injection elevated pH, and accelerated activation of calpains, resulting in improved tenderness. The rates of degradation of titin and troponin-T as well as the appearance of 95 and 30 kDa peptides were faster in the PPi-injected muscles than the controls. PPi-injection elevated muscle pH, which was attributed to acceleration of the calpain activation. It is concluded that PPi-injection improved beef tenderness by accelerating activation of calpain.