Abstract Gelation of aqueous solutions of casein micelles (MC) in mixtures with fractal aggregates of whey protein isolate (WPI) has been studied first by addition of different amounts of aggregates at a fixed concentration of micelles and then by substitution of micelles with aggregates at a fixed total protein concentration. Addition of small amounts of aggregates (1–5 g/L) to suspensions of micelles (20–60 g/L) at a fixed pH led to a strong decrease of the gelation temperature (Tg) and to an increase of the elastic modulus (G′) of the mixed gels. A minimum in Tg and a maximum in G′ as a function of the WPI fraction were obtained in mixtures with fixed total protein concentration and fixed pH and explained by the opposing influence of increasing WPI aggregate concentration and decreasing concentration of micelles. Increasing the total protein concentration at the same WPI fraction caused a decrease of Tg and increase of G′. Decreasing the pH at the same protein composition led to a decrease of Tg but caused an increase of G′. Tg decreased sharply if a small amount of CaCl2 was added, but if more than about 30 mM of calcium was added, Tg increased again. Gelation of mixtures did not depend significantly on the size of the WPI aggregates, but if fractal aggregates were replaced by microgels, weaker gels were produced and the temperature of gelation was higher. Potentiometric titration curves showed that protonation of the micelles and of the WPI aggregates in the mixtures was independent. It is concluded that MC and WPI aggregates co-aggregate during gelation and there is a transition between gelation at a critical temperature for pure MC suspensions and gelation controlled by an activation energy for pure WPI aggregate suspensions.

中文翻译：

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酪蛋白胶束与乳清蛋白聚集体混合物的热诱导凝胶化

摘要 酪蛋白胶束 (MC) 在与乳清蛋白分离物 (WPI) 分形聚集体混合物中的水溶液的凝胶化首先通过添加不同量的聚集体以固定胶束浓度进行研究，然后通过以一定浓度的聚集体取代胶束。固定总蛋白浓度。将少量聚集体 (1–5 g/L) 添加到固定 pH 值的胶束悬浮液 (20–60 g/L) 导致凝胶温度 (Tg) 大幅降低并增加弹性模量(G') 混合凝胶。在具有固定总蛋白质浓度和固定 pH 值的混合物中获得了作为 WPI 分数的函数的 Tg 最小值和 G' 最大值，并通过增加 WPI 聚集体浓度和降低胶束浓度的相反影响来解释。在相同的 WPI 分数下增加总蛋白质浓度导致 Tg 降低和 G' 增加。在相同蛋白质组成下降低 pH 会导致 Tg 降低但导致 G' 增加。如果添加少量 CaCl2，Tg 会急剧下降，但如果添加超过 30 mM 的钙，Tg 会再次上升。混合物的凝胶化并不显着依赖于 WPI 聚集体的大小，但如果分形聚集体被微凝胶取代，则产生较弱的凝胶并且凝胶化温度较高。电位滴定曲线表明混合物中胶束和 WPI 聚集体的质子化是独立的。