牦牛奶中不同酪蛋白的提取及其功能特性研究

Study on Extraction and Functional Properties of Different Casein in Yak Milk

本研究以新鲜牦牛乳为原料,添加钙盐后利用其等电点分离提取牦牛奶中的不同酪蛋白,利用单因素实验筛选牦牛奶中α-、β-、κ-酪蛋白的提取分离参数;并利用电泳(SDS-PAGE)分析牦牛乳不同酪蛋白纯度。同时对牦牛乳中α-、β-、κ-酪蛋白的溶解性、乳化性、发泡性进行分析比较。结果表明:牦牛奶不同酪蛋白分离的最佳Ca2+浓度为0.08 mol/L,最佳温度2℃,此时牦牛乳中α-、β-酪蛋白分离效果较好。牦牛乳不同酪蛋白在等电点(p I)附近时,α-、β-、κ-酪蛋白溶解性、乳化性、发泡能力最低,泡沫稳定性最好。等电点附近酪蛋白的溶解度最低,α-、β-酪蛋白pH值在2.1时溶解度最高(分别为60%、80%),而k-酪蛋白在pH值6.22时最高(43%);在40~80℃范围内,κ-酪蛋白溶解度受温度影响显著;当pH值为2.1时,α-、β-、κ-酪蛋白的乳化能力和发泡能力都最大,其乳化稳定性则是远离等电点后逐渐上升;本研究旨在为牦牛乳酪蛋白的利用和深加工提供思路,为云南特色乳制品的开发利用提供科学依据。

In this work,fresh yak milk was used as a raw material to separate and extract the different casein by adding calcium salt and employing its isoelectric point.Single factor experiments screened the extraction and separation parameters ofα-,β-,κ-casein in yak milk.SDS-PAGE was applied to analyze the purity of different casein in yak milk.At the same time,the solubility,emulsification,and foamability ofα-,β-,κ-casein in yak milk were analyzed and compared.The results showed that the optimum concentration of Ca2+and the optimum temperature for casein components separation in yak milk were 0.08 mol/L and 2℃,respectively.At this point,the separation effect ofα-andβ-casein in yak milk was better compared to the other.When different casein in yak milk was close to isoelectric point(p I),the solubility,emulsification,and foaming ability were at the lowest.On the contrary,the foam stability was at its best.The solubility of the casein component which was close to the isoelectric point was the lowest,the solubility ofα-,β-casein was at its highest at 2.1(60%,80%,respectively),while theκ-casein was at its highest at pH 6.22(43%).In the range between 40 and 80℃,the solubility ofκ-casein was significantly affected by temperature.In pH 2.1,the emulsification ability and foaming ability ofα-,β-,κ-casein were at the largest,and the emulsion stability was gradually increased from the isoelectric point.This study aimed to provide ideas for the utilization and advanced processing of yak milk casein,as well as providing a scientific basis for the development and utilization of Yunnan’s unique dairy products.