酰化修饰对牦牛乳酪蛋白结构及理化性质的影响

Influence of Acylation on the Structures and Physico-chemical Properties of Yak Caseins

摘要:

以丁二酸酐、丁二酸、乙酸酐为酰化试剂对牦牛乳酪蛋白进行酰化修饰，研究了酪蛋白空间结构、缓冲性能、钙镁磷含量、色度的变化。结果显示，丁二酸酐、乙酸酐、丁二酸酰化程度分别为90.0%、87.9%、18.5%。酰化修饰后，牦牛乳酪蛋白二级结构以转角和β-折叠的含量为主；丁二酸酐酰化促使酪蛋白形成少量规则的α-螺旋结构，含量为9.4%，其他样品中未检出。丁二酸酐酰化使其三级结构变化程度最大，丁二酸最小。酰化修饰后，牦牛乳酪蛋白最大荧光强度降低，除了乙酸酐修饰酪蛋白之外，其他样品最大发射波长红移；丁二酸修饰酪蛋白三级结构变化较小。酰化修饰后，酪蛋白缓冲性能增强。经酰化修饰后，牦牛乳酪蛋白中的钙、镁、磷含量均降低，但其色泽均变白。研究结果可为牦牛乳酪蛋白的改性及构效关系研究提供参考依据。

Abstract:

The influence of different acylation reagents (succinic anhydride, succinic acid and acetic anhydride) on the spatial conformation and physico-chemical properties of yak caseins were investigated. The secondary and tertiary structure, buffer capacity and calcium, magnesium, phosphorus content of original and modified yak caseins were also studied. The results showed that the acylation degree with succinic anhydride, acetic anhydride and succinic acid was 90.0%, 87.9% and 18.5%, respectively. After acylation with different reagents, the secondary structures of yak casein were mainly turn and β-sheet; a few α-helix structures formed after succinylated modification, with the content of 9.4%. Succinic anhydride had the largest influence on tertiary structure of casein, followed by acetic anhydride and succinic acid. The maximum ?uorescence intensity of intrinsic and ANS ?uorescence spectrum were reduced with modification and the maximum emission wavelength were shifted red except acetic anhydride modified casein. The modification improved the buffer capacity, reduced the content of calcium, magnesium, phosphorus. The color of modified caseins was whiter than original casein. The results could provide references for the chemical modification of yak caseins.