Department of Food Science, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark.
Meat Sci. 2010 May;85(1):110-4. doi: 10.1016/j.meatsci.2009.12.013. Epub 2009 Dec 13.
This study investigated the influence of post-mortem pH decline on calpain activity and myofibrillar degradation. From 80 pigs, 30 Longissimus dorsi (LD) muscles were selected on the basis of pH values at 3h post-mortem and classified into groups of 10 as fast, intermediate and slow pH decline. The rate of pH decline early post-mortem differed between the three groups, but the ultimate pH values were similar at 24h. Calpain activity and autolysis from 1 to 72h post-mortem were determined using casein zymography and studied in relation to myofibrillar fragmentation. Colour and drip loss were measured. A faster decrease in pH resulted in reduced level of mu-calpain activity and increased autolysis of the enzyme, and hence an earlier loss of activity due to activation of mu-calpain in muscles with a fast pH decline. Paralleling the mu-calpain activation in muscles with a fast pH decline a higher myofibril fragmentation at 24h post-mortem was observed, which was no longer evident in the later phase of the tenderization process. In conclusion, the rate of early pH decline influenced mu-calpain activity and the rate but not the extent of myofibrillar degradation, suggesting an early effect of proteolysis on myofibril fragmentation that is reduced during ageing due to an earlier exhaustion of mu-calpain activity.
本研究探讨了死后 pH 值下降对钙蛋白酶活性和肌原纤维降解的影响。从 80 头猪中选择了 30 块背最长肌（LD）肌肉，根据死后 3 小时的 pH 值进行分组，分为快速、中速和慢速 pH 值下降组，每组 10 块。三组间早期 pH 值下降速度不同，但 24 小时后的最终 pH 值相似。使用酪蛋白凝胶电泳法测定死后 1 至 72 小时的钙蛋白酶活性和自溶，并研究其与肌原纤维片段化的关系。测定颜色和滴水损失。更快的 pH 值下降导致 μ-钙蛋白酶活性降低和酶自溶增加，因此在 pH 值下降较快的肌肉中，由于 μ-钙蛋白酶的激活，酶活性较早丧失。与 pH 值下降较快的肌肉中的 μ-钙蛋白酶激活相一致，在死后 24 小时观察到更高的肌原纤维片段化，但在嫩化过程的后期阶段不再明显。总之，早期 pH 值下降速度影响 μ-钙蛋白酶活性和速度，但不影响肌原纤维降解的程度，表明蛋白酶解对肌原纤维片段化的早期影响，由于 μ-钙蛋白酶活性的早期耗尽，这种影响在老化过程中会减少。
