宰后肌肉蛋白质变化对冷却猪肉持水性的影响

对正常肉和PSE肉的蛋白质进行溶解性测定、DSC分析和SDS-PAGE电泳分析,结果显示,宰后1hPSE肉的肌浆蛋白和肌球蛋白的变性焓较低,宰后24h不同品质肉样间肌浆蛋白+肌球蛋白的变性焓、总蛋白变性焓和蛋白质溶解性存在明显差异。PSE肉的肌浆中45,40和22kDa蛋白质低于正常肉,而肌原纤维中100,25和24kDa蛋白质高于正常肉,225和16.6kDa低于正常肉。PSE肉的严重汁液流失是肌浆蛋白和肌球蛋白变性的结果,而宰后早期(6h前)的低pH是蛋白质变性的主要诱因;PSE肉蛋白质降解程度较高并和其严重的汁液流失有一定的关系。

Protein solubility, denaturation enthalpy and extent of proteolysis of protein from normal and PSE pork were determined. The results showed that PSE sample exhibited lower DHpeak Ⅰ＋Ⅱthan RFN sample at postmortem time of lh. Significant difference in protein solubility （sarcoplasmic, myofibrillar and total）, DHpeak Ⅰ＋Ⅱand DHtotal were observed between PSE and RFN at postmortem time of 24h. SDS-PAGE showed that in PSE sample a poorer band abundance of the 45, 40 and 22 kDa proteins in the sarcoplasmic fraction and a richer band abundance of the 100, 25 and 24 kDa proteins and poorer abundance of the 225 and 16.6 kDa proteins in the myofibrillar fraction. These data indicated that high drip loss of PSE was due to the denaturation of sarcoplasmic protein and myosin, which were the results from lower pH at early postmortem time. Extent of proteolysis in muscle accounted for the drip loss to some degree.