Thermal gelation of aqueous solutions of micellar casein (MC), whey protein isolate (WPI) and mixtures was investigated as a function of the total protein concentration and the composition at different pH between 5.8 and 6.6. The sol-gel state diagram was determined visually and the mechanical properties of the gels were studied by oscillatory shear rheology. The evolution of the shear moduli was measured as a function of heating time at different temperatures. Strong synergy between the two types of milk proteins was observed during gelation of mixtures. MC gels are formed above a critical temperature that increases with increasing concentration. The MC gels are reinforced by co-aggregation of denatured whey proteins. Hybrid gels display stronger elastic moduli and less syneresis than pure MC gels. The microstructure of the gels was assessed using confocal laser scanning microscopy and showed that hybrid gels were more homogeneous than pure MC gels. The structure of rapidly formed MC gels was not modified by subsequent co-aggregation with denatured WPI. The effect of electrostatic interactions was probed by comparing gelation of salt free solutions with that at 0.1 M NaCl. Addition of salt led to an increase of the minimal gel concentration of MC.

中文翻译：

---

pH和NaCl对加热后的乳清蛋白分离物和酪蛋白胶束混合物的微观结构和流变学的影响

研究了胶束酪蛋白（MC），乳清蛋白分离物（WPI）和混合物的水溶液的热凝胶化，其是总蛋白浓度和在5.8至6.6之间的不同pH下组成的函数。目视确定溶胶-凝胶状态图，并通过振荡剪切流变学研究凝胶的机械性能。测量在不同温度下剪切模量随加热时间的变化。在混合物凝胶化过程中，观察到两种类型的牛奶蛋白之间具有强大的协同作用。MC凝胶在临界温度以上形成，该临界温度随浓度增加而增加。MC凝胶通过变性乳清蛋白的共聚集而得到增强。杂化凝胶显示出比纯MC凝胶更强的弹性模量和更少的脱水收缩。使用共聚焦激光扫描显微镜评估凝胶的微观结构，结果表明杂化凝胶比纯MC凝胶更均匀。快速形成的MC凝胶的结构未通过随后与变性WPI的共聚集进行修饰。通过比较无盐溶液的凝胶化和在0.1 M NaCl溶液中的凝胶化来探究静电相互作用的影响。盐的加入导致MC的最小凝胶浓度增加。