蛋白质降解指示冷藏罗非鱼片品质劣变研究

Protein Degradation Indicating Quality Deterioration of Chilled Tilapia Fillets

通过测定蛋白分解菌、蛋白降解产物、蛋白溶解性以及肌原纤维蛋白和肌浆蛋白的十二烷基硫酸钠-聚丙稀酰胺凝胶电泳(SDS-PAGE)条带变化反映蛋白降解作用对冷藏罗非鱼片腐败进程的影响。结果表明:蛋白分解菌、pH值、氨基态氮含量的变化与肌肉蛋白降解程度具有良好对应关系。当蛋白分解菌少于6.10(lg(CFU/g))时,pH值呈弱酸性,氨基态氮含量无明显增加,肌原纤维蛋白和肌浆蛋白的SDS-PAGE条带模式无明显变化。当蛋白分解菌不少于7.60(lg(CFU/g))时,pH值呈中性至弱碱性,氨基态氮快速增加,SDS-PAGE条带开始扩展分解,蛋白降解作用持续增强。当肌原纤维蛋白SDS-PAGE中中45～29kD处第3条带消失,并在小于等于29kD处出现新条带时是鱼肉腐败的重要标志。

The effect of protein degradation on the spoilage progress of chilled tilapia fillets was evaluated by measuring proteolytic bacteria, proteotytic compounds, protein solubility, and SDS-PAGE patterns of myofibrilar protein and sarcoplasmic protein. The results showed that the extent of muscle protein degradation was associated with changes in proteolytic bacteria, pH and amino nitrogen. When proteolytic bacteria were less than 6.10 （lg（CFU/g））, weakly acidic pH and no obvious changes in amino nitrogen or SDS-PAGE patterns of myofibrilar protein and sarcoplasmic protein were observed. While proteolytic bacteria reached or exceeded 7.60 （lg（CFU/g））, neutral or alkaline pH, a rapid increase in amino nitrogen, and outspread strips indicating protein degradation in SDS-PAGE patterns were observed. Therefore, the disappearance of the third band （45-29 kD） and the appearance of new bands with a molecular weight less than or equal to 29 kD in SDS-PAGE pattern of myofibrilar protein may be an important indicator of protein degradation.