Gelation of the complex between kappa-casein and beta-lactoglobulin.

The gelation of the complex between kappa-casein and beta-lactoglobulin was examined. The apparent viscosity of the mixture of kappa-casein and beta-lactoglobulin increased by heat treatment. The mixture formed a gel at the concentration of 8% (w/w). The gel formation was accelerated by the chymosin treatment. The mixture of kappa-casein and beta-lactoglobulin in each concentration of 1.5% gelled by the addition of chymosin after heat treatment. Forming the complex between kappa-casein and beta-lactoglobulin was necessary to the gel formation. Therefore, heat treatment of above 70 degrees C was demanded. Turbidity increased and the relative content of soluble protein decreased accompanied with gel formation. The addition of calcium ion to the heated solution produced an increase in turbidity. The larger the protein concentration was, the larger the breaking stress of the formed gel was. The addition of calcium ion weakened the breaking stress of the gel.