Mixtures of sodium caseinate and whey protein aggregates: Viscosity and acid- or salt-induced gelation

Mixtures of sodium caseinate (SC) and whey protein aggregates (WPA) were investigated at different compositions, protein concentrations and temperatures. Potentiometric titration suggests that no complexes between SC and WPA were formed, at least in the pH range 4-7. The viscosity increased when SC was substituted with large fractal WPA and decreased when substituted with whey protein microgels, and followed a logarithmic mixing rule. Gelation of mixtures of fractal WPA and SC was induced by adding CaCl2 or acidification. Addition of SC did not have an effect on the elastic modulus and the microstructure properties of acid- or salt-induced gels formed by WPA, but the rate of gelation decreased with increasing SC concentration, even though the activation energy remained the same. This effect was attributed to binding of Ca2+ to SC and a reduction of the effective amount of Ca2+ available for binding to WPA.