Heat-induced gelation of casein micelles in aqueous suspensions at different pH

Heat-induced gelation of casein micelles in aqueous solution was investigated between pH 5.2 and pH 6.7 over a wide range of protein concentrations (C = 25–160 g L−1). For C ≥ 40 g L−1 the casein micelles rapidly formed a self-supporting gel above a critical temperature (Tc). At C = 160 g L−1, Tc decreased from 90 °C at pH 6.5 to 30 °C at pH 5.4 and increased with decreasing protein concentration. Oscillatory shear measurements during heating showed that the elastic modulus (Gel) of the gels increased strongly with increasing protein concentration, but was insensitive to the pH and the heating temperature except close to Tc where Gel decreased sharply with decreasing temperature. The microstructure of the gels was observed by confocal scanning laser microscopy. Heat-induced gelation of casein micelles was compared with that of sodium caseinate solutions free of calcium phosphate.