Gelation of commercial fractions of beta-lactoglobulin and alpha-lactalbumin

Commercial fractions of alpha-lactalbumin (alpha-fraction) and beta-lactoglobulin (beta-fraction) were studied to characterize and define their gelation behaviour. Gels were obtained from the beta-fraction at a solution concentration of 100gL(-1) at 85 degrees C, 110gL(-1) at 80 degrees C, 120gL(-1) at 75 degrees C and 140gL(-1) at 70 degrees C, while the alpha-fraction produced gels at concentrations above 130gL(-1) at 85 degrees C, but not at lower temperatures. Salt concentration and pH had significant effects (p < 0.05) on the formation, strength and viscoelastic behaviour of the gels. The rigidity of the gels from either fraction increased significantly (p < 0.05) at pH 6.8, 7.0 and 7.5 when the concentration of NaCl was increased to 20mM. The addition of low levels of alpha-fraction to beta-fraction at constant total protein concentration increased the gelation behaviour compared to the beta-fraction alone; however, it appeared that a maximum concentration of alpha-lactalbumin existed for this synergistic behaviour. (C) 1997 Elsevier Science Limited.