猪宰后肌肉体系中μ-calpain及肌原纤维蛋白理化特性的变化规律  

The Variations in μ-Calpain and Physico-Chemical Characteristics of Myofibrillar Proteins in Postmortem Porcine Muscle

作　　者：魏秀丽[1] 谢小雷[1] 张春晖[1] 李侠[1] 王春青[1] 

机构地区：[1]中国农业科学院农产品加工研究所/农业部农产品加工综合性重点实验室,北京100193

出　　处：《中国农业科学》2015年第12期2428-2438,共11页Scientia Agricultura Sinica

基　　金：国家自然科学基金(31271902);国家公益性行业(农业)科研专项(201303083)

摘　　要：【目的】研究猪宰后1—168 h,肌肉体系中μ-calpain及肌原纤维蛋白理化特性变化规律,并探究肌肉持水性变化机理,为冷鲜肉汁液流失控制提供理论依据。【方法】取宰后1 h内的猪背最长肌,在4℃条件下分别成熟6、12、24、72、120和168 h,通过活性电泳(casein zymography)对μ-calpain活性定量分析,对肌原纤维小片化指数(myofibril fragmentation index,MFI)进行过程测定,利用SDS-PAGE变性凝胶电泳分析肌原纤维蛋白降解聚合情况,研究宰后肌肉的成熟与肌原纤维蛋白的结构变化规律;通过测定肌原纤维蛋白表面疏水性和溶解性,考察肌原纤维蛋白水合力的变化,利用加压滤纸法测定肌肉的持水性(water-holding capacity,WHC),并借助低场核磁共振技术(low field nuclear magnetic resonance,LF-NMR)定性定量考察肌肉3种不同状态水(结合水、不易流动水及自由水)的分布和迁移。【结果】宰后1—24 h,μ-calpain活性升高,肌原纤维蛋白未发生明显降解,MFI无显著变化(P>0.05)。宰后24 h肌肉进入成熟期,μ-calpain活性逐渐下降,MFI值显著升高(P<0.05),肌原纤维蛋白显著降解,肌肉持水性随之改变。肌肉成熟过程中,μ-calpain作用于肌肉蛋白导致蛋白质结构伸展并降解,一方面会有低分子量的蛋白生成,增加蛋白质的比表面积,使其溶解度增加;另一方面也有疏水残基的暴露及蛋白的交联聚合,导致蛋白溶解度降低,表面疏水性增加,这两者之间的竞争结果决定了降解后蛋白质的水合特性。其中,宰后24—120 h,μ-calpain适度降解肌原纤维蛋白,溶解度显著升高(P<0.05),使肌肉中不易流动水P22升高(r=0.286,P<0.01),自由水P23下降(r=-0.246,P<0.05);肌原纤维蛋白内部疏水性残基的暴露引起表面疏水性显著升高(P<0.05),致使肌肉自由水P23升高(r=0.319,P<0.01);LF-NMR-T2结果表明结合水P21与不易流动水P22的相关系数为r=-0.890(P<0.01),不易流动水P22与自由水P23的�【Objective】Variations in μ-calpain and physico-chemical characteristics of myofibrillar proteins in relation to the water-holding capacity in postmortem porcine muscle（1-168 h） were investigated. The study was expected to provide theoretical supports to regulate the unacceptable high drip loss of muscle and meat postmortem.【Method】Samples of porcine M. longissimus dorsi was collected for μ-calpain activity by casein zymography, myofibril fragmentation index, SDS-PAGE, myofibrillar protein surface hydrophobicity and solubility, water-holding capacity analysis. And low-field nuclear magnetic resonance relaxation T2（LF-NMR T2） analysis of water mobility and distribution was also carried out.【Result】During the 1 h to 24 h postmortem, μ-calpain activity increased, while no significant changes of myofibrillar proteins degradation and MFI values were observed. Significant decreases of μ-calpain activity, with the increases in MFI occurred at 24 h postmortem, which revealed the conversion of muscle into meat. Proteolysis of muscle proteins by μ-calpain, on the one hand gave a rise in protein solubility because of more low molecular proteins emerged, on the other hand led to higher surface hydrophobicity and lower solubility due to hydrophobic groups in protein exposure to its surface and protein aggregation. Both contributed to the protein hydration characteristics. Changes of protein hydration capacity affected the attributes of muscle water populations. During the 24 h to 120 h postmortem, proteolysis degradation of myofibrillar proteins by μ-calpain occurred. The improvements of protein solubility led to the decreased population of free water P23（r=-0.246, P0.05）and increased population of immobilized water P22（r=0.286, P0.01）. Meanwhile, the exposure of hydrophobic residues resulted in increases of surface hydrophobicity, which was accompanied with decreases of the population of free water P23（r=0.319, P0.01）. T2 relaxation patterns data indicated that protein-associated water wa

关 键 词：猪 宰后成熟 μ-钙激活酶 肌原纤维蛋白 水合特性 持水性 水分迁移 

分 类 号：S828[农业科学—畜牧学]