不同年龄牦牛宰后钙激活酶活性及嫩度指标变化

本研究对不同年龄牦牛宰后成熟过程中钙激活酶活性和嫩度指标（肌纤维直径、肌原纤维小片化指数（myofibrillar fragmentation index，MFI）、肌原纤维超微结构）进行测定。结果表明：成熟过程中，不同年龄牦牛肉肌纤维直径、MFI都发生显著变化（P＜0.05），肌原纤维在成熟过程中Z线断裂，框架结构被完全破坏；钙激活酶活性在宰后的前2 d均显著下降（P＜0.05），且成熟过程中不同年龄公牦牛的钙激活酶活性均高于母牦牛；成熟时间与钙激活酶活性、嫩度指标均成极显著相关性（P＜0.01）；牦牛宰后经过7 d的成熟，可以降低牦牛因屠宰年龄不同而产生的差异，同时也可以改善肉的嫩度；与公牦牛相比母牦牛宰后成熟时间可以适当的延长。

Changes of Calpain Activity and Tenderness Indexes during Postmortem of Yak Meat from Different Aged Yaks

In this study, the tenderness indexes (muscle fiber diameter (MFI) and myofibril ultrastructure) and calpain
activity of the meat of yaks of different ages during postmortem were measured. The results showed that MFI of yak meat
at different ages significantly changed (P < 0.05), myofibril ultrastructure was completely disrupted, Z line was ruptured,
and calpain activity was significantly decreased (P < 0.05) during aging. In addition, calpain activity of male yak meat was
higher than that of female yak meat during aging. The aging time showed a significant correlation with tenderness indexes
and calpain activity (P < 0.01). After seven days, the distinction of yak meat at different ages was decreased; meanwhile, the
tenderness of meat was improved. The aging time of male yak meat was longer than that of female yak meat.