Heat-induced denaturation and aggregation of beta-Lactoglobulin: kinetics of formation of hydrophobic and disulphide-linked aggregates

Solutions of a whey protein mixture were subjected to various time/temperat ure treatments, at pH 6.7. Kinetic and thermodynamic activation parameters for the rates of irreversible denaturation/aggregation of the principal whe y protein component-beta-lactoglobulin (beta-1g) were followed by gel perme ation. Fast Protein Liquid Chromatography (non-dissociating, non-reducing c onditions) and by SDS-PAGE (dissociating, non-reducing conditions). The rat e of loss of native beta-1g owing to the formation of disulphide linked pro tein aggregates (k(SDS-PAGE)) and the rate of formation of aggregates via b oth covalent and non-covalent bonds (k(GP-FPLC)) showed similar biphasic Ar rhenius plots. However, the break of the plot occurred at different points. The k(GP-FPLC) Values were higher than values of k(SDS-PAGE) for all the t emperatures examined. There was a similar trend for the thermodynamic activ ation parameters implying that not all of the beta-1g aggregates through th iol-disulphide interactions. Hydrophobically driven associations occur with in the aggregates.