INTERACTIONS OF ALPHA-LACTALBUMIN AND BOVINE SERUM-ALBUMIN WITH BETA-LACTOGLOBULIN IN THERMALLY INDUCED GELATION

The interactions of alpha-lactalbumin and bovine serum albumin (BSA) with beta-lactoglobulin in mixed-protein gel systems were investigated by dynamic oscillation rheology and aggregation rates. BSA and alpha-lactalbumin were found to contribute to the storage modulus (G') of mixed-protein gels made primarily with beta-lactoglobulin. Gels made with beta-lactoglobulin alone, or combinations of alpha-lactalbumin and beta-lactoglobulin, had similar transitions and ultimate values for G'. In contrast, the rheological transitions and properties of gels made with mixtures of beta-lactoglobulin and BSA were dependent on the ratio of proteins in the mixture. Second-order aggregation rate constants of alpha-lactalbumin, beta-lactoglobulin, and BSA heated alone at 80-degrees-C were in the order BSA much greater than beta-lactoglobulin > alpha-lactalbumin. The aggregation rate of alpha-lactalbumin increased when heated in combination with beta-lactoglobulin, suggesting a coaggregation of proteins. These results indicate that rheological properties of whey protein gels can be altered by changing the ratios of constitutive proteins.