Abstract: In order to investigate the effect of myofibrillar protein on postmortem meat quality and to determine the best post-mortem aging time for Sunit sheep carcasses, the Biceps femoris of Sunit lambs slaughtered at six months of age was evaluated for meat quality, myofibrillar protein functional characteristics, and protein degradation-related indicators during post-mortem aging (from day 0 to 3). The results showed that three meat quality attributes (pH, shear force, and cooking loss rate) reached optimal values on the second day of post-mortem aging, not significantly different from those recorded on the third day. On the first day, the functional properties of myofibrillar protein including hydration properties (solubility and hydrophobicity), gel properties (water-holding capacity and hardness) and emulsifying properties (emulsifying activity index (EAI), emulsion stability index (ESI)) were poor, improved on the second day and then leveled off. Measurement of myofibril fragmentation index (MFI) and sodium dodecylsulphate-polyacrylamide gel electrophoresis indicated that the degree of protein degradation was low on the second day and thereafter remained stabled. Correlation analysis demonstrated that MFI, solubility, hydrophobicity, EAI, ESI, and gel water-holding capacity were correlated with meat quality indicators. In summary, during the post-mortem aging of Sunit sheep carcasses, the degradation of myofibrillar protein and changes in its functional characteristics had a great impact on meat quality, and the best post-mortem aging time was two days.

Key words: Sunit sheep; post-mortem aging; meat quality; myofibrillar protein