HEAT-INDUCED INTERACTIONS AND GELATION OF MIXTURES OF BETA-LACTOGLOBULIN AND ALPHA-LACTALBUMIN

The changes in protein aggregation and storage modulus of mixtures of beta-lactoglobulin and alpha-lactalbumin were measured, by gel electro phoresis and dynamic rheology, respectively, during 60 min of heating at 75 or 80 degrees C in a buffer simulating the whey protein concentr ate environment. The results were consistent with the formation of hea t-induced hydrophobically bonded aggregates involving both alpha-lacta lbumin and beta-lactoglobulin that under go disulfide bond interchange reactions within the aggregate as the basis for the generation of gel strands and gels. The apparent difference in response to heat treatme nt at 75 degrees C between mixtures of bovine serum albumin (BSA) and beta-lactoglobulin and mixtures of alpha-lactalbumin and beta-lactoglo bulin is likely to be based on at least three factors: the different t hermal transition temperatures of the three proteins; the possibility of self-initiation of thiol-disulfide interchange reactions for BSA an d beta-lactoglobulin, but not alpha-lactalbumin; and the ability of al pha-lactalbumin to form interprotein aggregates with each of the other two proteins prior to disulfide bond interchange and gelation.