Effects of Ultimate pH on the Properties of Myofibrillar Proteins from Ovine Muscle during Postmortem Aging

This study was aimed to investigate effects of muscle ultimate pH (pH_u) on titin, nebulin, desmin, troponin-T degradation and myofibril fragmentation index (MFI) in ovine muscle. After 50 animals were slaughtered, the right longissimus lumborum (LL) muscles were stored at 4℃ for 7 d. Based on muscle the pH at post-mortem 2 d, muscles were classified into three groups:the high pH_u (5.72±0.03), intermediate pH_u (5.54±0.01) and low pH_u (5.40±0.02) muscles. Muscle pH, MFI and degradation of titin, nebulin, desmin and troponin-T were measured at 1 h, 1, 2, 3, 5 and 7 days postmortem. The data obtained showed that titin started to the degradation in the high pH_u muscles on day 1 postmortem. On day 1 postmortem, the intensity of desmin was lowest in the high pH_u muscles than that that in intermediate and low pH_u (p<0.05). Degradation of troponin-T occurred on day 1 postmortem in the high pH_u muscles. But degradation of nebulin was observed on day 1 postmortem in the intermediate pH_u muscles. At the same time, meat in high and intermediate pH_u groups had higher MFI than that in low pH_u group at 1, 2, 3, 5 and 7 days postmortem (p<0.05). The study showed that muscle ultimate pH influenced the degradation of these myofibrillar proteins postmortem and thus meat tenderization. Degradation of titin, desmin and troponin-T improved directly meat tenderness in early stage of ageing. This provided a theoretical basis for mechanisms involved in tenderization of meat.