Postmortem calpain changes in ostrich skeletal muscle

The objective of this study was to study the postmortem calpain change in ostrich muscle. Iliotibialis cranialis and Obturatorius medialis muscles were removed from the both sides of carcasses (n=8). The muscles from the left side were sampled after 0, 1, 2, 3, and 7days of storage at 5°C, while the right-side muscles were taken at 1-, 3-, and 7-day postmortem for shear force measurements. The results showed that the calpain-1 activity was not detected in ostrich muscle during the entire 7-day postmortem storage period, while the calpain-11 was. The unautolyzed calpain-11 activity decreased and the autolyzed calpain-11 activity increased with time postmortem. Desmin content and shear force did not change during postmortem storage although a minor degradation of desmin was observed. Therefore, our results suggest that limited postmortem proteolysis (as suggested by the limited degradation of desmin) and tenderization might be due to the lack of calpain-1 and/or insufficient calpain-11 activity present in ostrich muscle.