不同热杀菌条件对羊乳乳清蛋白和酪蛋白结构与功能特性的影响

Effects of Different Thermal Sterilization Conditions on Structural and Functional Properties of Whey and Casein Proteins in Goat Milk

为了探究不同热杀菌条件对羊乳乳清蛋白和酪蛋白结构与功能特性的影响,选取工业常用的杀菌条件65℃、30 min,80℃、30 s,95℃、5 min和135℃、4 s处理羊乳,并分离羊乳乳清蛋白和酪蛋白;采用圆二色光谱仪、傅里叶变换红外光谱仪、荧光分光光度计、激光共聚焦扫描显微镜、原子力显微镜分析蛋白结构与特性变化情况。结果表明,65℃、30 min和80℃、30 s处理的乳清蛋白和酪蛋白结构变化较小,蛋白展开与表面疏水性的增加使得乳清蛋白和酪蛋白具有更好的起泡特性和乳化特性。95℃、5 min和135℃、4 s处理使蛋白的α-螺旋相对含量显著降低,无规卷曲相对含量显著增高,蛋白严重变性,溶解度与表面疏水性的降低会对羊乳蛋白功能特性以及稳定性产生不利影响。综上,本研究揭示了羊乳乳清蛋白和酪蛋白在不同杀菌温度条件下的变化规律,可为优化羊乳制品的品质和稳定性提供参考,有助于开发更具有功能性的羊乳产品。

This study investigated the effects of different thermal sterilization conditions on the structural and functional properties of whey and caseins in goat milk.The commonly used industrial sterilization conditions including 65 ℃ for 30 min,80 ℃ for 30 s,95 ℃ for 5 min and 135 ℃ for 4 s were selected to treat goat milk,and whey and casein proteins were separated from the treated milk.Circular dichroism(CD) spectroscopy,Fourier transform infrared(FTIR) spectroscopy,fluorescence spectroscopy,laser confocal scanning microscopy(LCSM) and atomic force microscopy(AFM) were used to analyze the changes in protein structure and properties.The results showed that the structures of whey and casein proteins changed little after treatment at 65 ℃ for 30 min and 80 ℃ for 30 s,and the increase in protein unfolding and surface hydrophobicity resulted in better foaming and emulsifying properties of whey and casein proteins.The treatments at 95 ℃for 5 min and 135 ℃ for 4 s resulted in a significant decrease in the relative content of α-helix,a significant increase in the relative content of random coil,severe denaturation of the proteins,and a decrease in solubility and surface hydrophobicity,which adversely affected the stability of functional properties of goat milk proteins.The above results provide a reference for optimizing the quality and stability of goat milk products,and help to develop functional goat milk products.