Heat-Induced Interactions and Gelation of Mixtures of β-Lactoglobulin and α-Lactalbumin

The changes in protein aggregation and storage modulus of mixtures of β-lactoglobulin and α-lactalbumin were measured, by gel electrophoresis and dynamic rheology, respectively, during 60 min of heating at 75 or 80 °C in a buffer simulating the whey protein concentrate environment. The results were consistent with the formation of heat-induced hydrophobically bonded aggregates involving both α-lactalbumin and β-lactoglobulin that undergo 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 treatment at 75 °C between mixtures of bovine serum albumin (BSA) and β-lactoglobulin and mixtures of α-lactalbumin and β-lactoglobulin is likely to be based on at least three factors: the different thermal transition temperatures of the three proteins; the possibility of self-initiation of thiol−disulfide interchange reactions for BSA and β-lactoglobulin, but not α-lactalbumin; and the ability of α-lactalbumin to form interprotein aggregates with each of the other two proteins prior to disulfide bond interchange and gelation. Keywords: Whey protein concentrate; hydrophobic aggregation; disulfide bonding