Inhibition and Promotion of Heat-Induced Gelation of Whey Proteins in the Presence of Calcium by Addition of Sodium Caseinate.

Heat-induced aggregation and gelation of aqueous solutions of whey protein isolate (WPI) in the presence of sodium caseinate (SC) and CaCl was studied at pH 6.6. The effect of adding SC (0-100 g/L) on the structure of the aggregates and the gels was investigated by light scattering and confocal laser scanning microscopy at different CaCl concentration ([CaCl] = 0-30 mM). The gelation process was studied by oscillatory shear rheology. At the whey protein concentrations studied here (34 and 60 g/L), no gels were formed in the absence of CaCl and SC. However, WPI solutions gelled above a critical CaCl concentration that increased with increasing SC concentration. In the absence of CaCl, WPI gels were formed only above a critical SC concentration. The critical SC concentration needed to induce WPI gelation decreased weakly when CaCl was added. In an intermediate range of CaCl concentrations, gels were formed both at low and high SC concentrations, but not at intermediate SC concentrations. Finally, at high CaCl concentrations gels were formed at all SC concentrations. The gelation rate and the gel structure of the gels formed at low and high casein concentrations were very different. The effect of SC on the thermal gelation of WPI was interpreted by competition for Ca, a chaperon effect, and microphase separation.