不同嫩度羊肉中钙蛋白酶的差异

【目的】钙蛋白酶是宰后肌肉嫩化过程的主要贡献者,通过蛋白水解能力发挥其功能作用。钙蛋白酶,尤其是μ-钙蛋白酶(μ-calpain)的活性与宰后肌肉的嫩度密切相关。探究不同嫩度的羊肉中钙蛋白酶的差异,确定羊宰后肌肉中μ-钙蛋白酶的主要作用时间及其与嫩度的关系,为调控钙蛋白酶酶活进而调控嫩度提供理论基础。【方法】选取乌珠穆沁大尾羊背最长肌为样品,通过测定肌原纤维小片化指数将样品进行高、低嫩度分组,分别测定嫩度差异样品在宰后成熟过程中p H、μ-钙蛋白酶大亚基存在状态,以及未自溶μ-/m-钙蛋白酶的含量随宰后时间的变化情况。【结果】高、低嫩度组宰后p H的变化规律一致,宰后各时间点两组样品p H均差异不显著。μ-钙蛋白酶80 k Da大亚基在宰后逐渐降解,宰后30 min,高嫩度组μ-钙蛋白酶80 k Da大亚基含量显著高于低嫩度组;但高嫩度组μ-钙蛋白酶80 k Da大亚基在宰后48 h已基本完全降解,低嫩度组在宰后5 d才基本完全降解。未自溶μ-钙蛋白酶的含量逐渐下降,宰后30 min和2 h,高嫩度组未自溶μ-钙蛋白酶的含量显著高于低嫩度组,宰后12 h、5 d和7 d,低嫩度组未自溶μ-钙蛋白酶的含量显著高于高嫩度组。宰后6 h,高嫩度组μ-钙蛋白酶出现明显的自溶和降解现象。【结论】与低嫩度组相比,高嫩度组宰后μ-钙蛋白酶的初始含量较高,但高嫩度组μ-钙蛋白酶自溶、失活的速率快,自溶及激活程度显著大于低嫩度组。表明宰后μ-钙蛋白酶的自溶及激活状态直接影响肌肉的嫩度。宰后24 h,尤其是12 h内,μ-钙蛋白酶的变化状态对羊肉嫩度的影响最大。

Analysis and Comparison of Calpain in Mutton with Different Levels of Tenderness

【Objective】Calpain plays an important role in postmortem tenderization through the proteolysis ability. The activity of calpains, especially μ-calpain, is closely related to the tenderness of muscles. The objective of this study was to investigate the activation process and the autolysis rate of μ-calpain in mutton during postmortem aging by analyzing and comparing the differences of calpain in mutton with different levels of tenderness, thereby provide a theoretical basis for regulating tenderness through regulating calpain activity. 【Method】 The longissimus dori of WuZhuMuQin Fat Tailed sheep were divided into tender group and tough group based on myofibrillar fragmentation index, then the pH value, the existent state of μ-calpain large subunit and the content of native μ-/m-calpain during postmortem were analyzed. 【Result】The variation trend of pH at postmortem in tender/tough group was identical, all the pH values in two groups at the same postmortem time showed no difference. The 80 kDa subunit of μ-calpain degraded gradually after slaughter. The content of μ-calpain 80 kDa subunit of tender group was significantly higher than tough group at 30 min postmortem. The intact 80 kDa subunit of μ-calpain could not be detected after 48 h in tender group, while it could be detected until 5 d postmortem in tough group. The content of native μ-calpain was decreased gradually, and this content of tender group was significantly higher than tough group at 30 min, 2 h postmortem, however, at 12 h, 5 d, and 7 d postmortem the tough group was significantly higher than the tender group. The autolysis and degradation of μ-calpain in tender group was apparent at 6 h postmortem.【Conclusion】Compared with tough group, tender group had a higher initial μ-calpain content, but the autolysis and degradation rate of μ-calpain in tender group was much faster, leading higher autolysis and degradation degree in tender group. The results indicated that meat tenderness during the postmortem was directly affected by μ-calpain expression quantity and autolysis. In addition, changes of μ-calpain during 24 h postmortem, especially 12 h, had the most impact on mutton tenderness.