为探究快速冷却对宰后牦牛肉成熟过程中嫩度与细胞凋亡酶活力的关系，以常规冷却和快速冷却处理的牦牛背最长肌为研究对象，分别在宰后不同时间点测定剪切力、肌原纤维小片化指数（myofibrillar fragmentation index，MFI）、caspase-9、3活力等指标变化。结果表明，快速冷却处理使宰后初期肌肉中心温度下降速率加快，pH下降速率降低。在宰后6 h内，MFI、caspase-9活力变化不显著（p>0.05）。pH、剪切力、caspase-9、3活力出现峰值时间延迟。此外，与常规冷却相比，快速冷却组剪切力值普遍较高，MFI较低。宰后168 h，快速冷却组与常规冷却组MFI分别升高了56.59%、58.60%，差异显著（p<0.05）。以上研究表明，快速冷却方式下温度下降速率的提高显著减缓了pH的下降，使caspase活力在成熟前期被抑制，导致其对肌原纤维蛋白的降解减弱，从而降低牛肉嫩度并延长肌肉成熟时间。

In order to explore the relationship between the tenderness and the apoptotic activity during yak meat postmortem aging. The longissimus dorsi muscles of the yak treated by conventional chilling and rapid chilling were taken as experiment objects. The changes of shear force, myofibrillar fragmentation index (MFI) and caspase-9,3 activity at different time points in postmortem were measured. The results indicated that rapid chilling accelerated the rate of decrease of temperature in the muscle center and decreased the rate of drop of pH value in early postmortem aging. The rapid chilling led to no significant change in activity of caspase-9 and MFI within 6 h in postmortem (p>0.05), which delayed the peak times of pH value, shear force and caspase-9,3 activities. In addition, the shear force value in rapid chilling group was higher than the value in conventional chilling group, and the MFI was lower in rapid chilling group compared to conventional chilling group. The MFI in rapid chilling group and conventional chilling group increased by 56.59% and 58.60%, respectively, at 168 h in postmortem aging, the difference was significant (p<0.05). The above research shows that the increase of temperature reduction rate during rapid chilling significantly slows down the reduction rate of pH, so that the apoptotic activity was inhibited in the early postmortem aging, leading to the weak degradation of myofibrillar protein, which reduced the tenderness of beef and prolonged the aging time of muscle.

国家自然科学基金项目（31560463）；甘肃省财政厅专项和国家肉牛牦牛产业技术体系项目（CARS-37）