Contribution of calpain to protein degradation, variation in myowater properties and the water-holding capacity of pork during postmortem ageing.

To investigate calpain's effect on protein degradation, myowater properties, and the water-holding capacity (WHC), porcine longissimus muscles were incubated with control buffer, PD150,606 (calpain-specific inhibitor) and MG-262 (multiple-protease inhibitor) and assigned to an ageing period of 1, 4 or 7 d. Over 7 d of storage, no significant differences (P > 0.05) were observed in desmin or integrin expression between the MG-262 and PD150,606 groups, which indicated that calpain played a major role in protein proteolysis. Compared to those in the control group, muscle samples subjected to PD150,606 and MG-262 exhibited higher water mobility and a poorer WHC. Additionally, there were no significant differences in myowater properties or the WHC between the two groups at 1 d postmortem (P > 0.05). Calpain regulated the distribution and mobility of myowater, which contributed to a higher WHC in the early postmortem period (before 4 d), but other proteases tended to take over at a later stage.