热诱导温度与pH值对乳清浓缩蛋白凝胶结构和性质的影响

以乳清浓缩蛋白（whey protein concentrate，WPC）为原料，采用动态流变仪、光学微流变仪、圆二色谱仪、荧光分光光度计及扫描电镜探究WPC凝胶形成过程、分子间相互作用和微观结构，并研究热诱导温度（60、85 ℃）和pH值（2.0、4.5、7.0、9.0）对WPC凝胶性质和结构的影响机理。结果表明：pH值通过改变电荷密度影响WPC的凝胶结构；热诱导温度为85 ℃时，蛋白质分子展开更充分，α-螺旋结构含量较低，内源荧光的最大荧光强度波长处红移明显，形成的WPC凝胶具有更高的弹性模量和黏性模量；凝胶的弹性因子和宏观黏度指数较高，固液平衡值较低；相互作用力分析结果说明较高的热诱导温度能促进疏水相互作用、氢键与二硫键的形成，从而改善WPC凝胶的性质和结构。

Effect of Heating Temperature and pH on the Structure and Properties of Whey Protein Concentrate Gels

The objective of this study was to explore the formation process, molecular interactions, and microstructure of whey protein concentrate (WPC) gels by a dynamic rheometer, a microrheometer, a circular dichroism spectrometer, a fluorescence spectrophotometer and a scanning electron microscope (SEM). Furthermore, the mechanisms for the effects of heating temperature (60 and 85 ℃) and pH (2.0, 4.5, 7.0 and 9.0) on the properties and microstructures of WPC gels were discussed. The results indicated that pH affected the gel structure by changing the charge density of WPC. After heat treatment at 85 ℃, the protein molecules were unfolded more sufficiently and exhibited a lower content of α-helix structure. In addition, the wavelength of maximum endogenous fluorescence intensity was red-shifted. The WPC gel formed at 85 ℃ showed higher elastic and viscous moduli as well as elasticity index and macroscopic viscosity index, and lower solid-liquid balance value. In addition, higher temperature could promote the formation of hydrogen bonds, disulfide bonds and hydrophobic interactions, thus improving the properties and microstructure of WPC gels.