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

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*Correspondent: Fax: +44 113 233 2982;e-mail: R.K.Owusu@1Leeds.ac.uk1 Current address: Cambridge University Chemical Laboratory, Cambridge University, Lensfield Road, Cambridge, CB2 1EW, UK.

Abstract

Summary Solutions of a whey protein mixture were subjected to various time/temperature treatments, at pH 6.7. Kinetic and thermodynamic activation parameters for the rates of irreversible denaturation/aggregation of the principal whey protein component—β-lactoglobulin (β-lg) were followed by gel permeation. Fast Protein Liquid Chromatography (non-dissociating, non-reducing conditions) and by SDS-PAGE (dissociating, non-reducing conditions). The rate of loss of native β-lg owing to the formation of disulphide linked protein aggregates (ksds-page) and the rate of formation of aggregates via both covalent and non-covalent bonds (kgp-fplc) showed similar biphasic Arrhenius plots. However, the break of the plot occurred at different points. The kgp-fplc values were higher than values of ksds-page for all the temperatures examined. There was a similar trend for the thermodynamic activation parameters implying that not all of the β-lg aggregates through thiol–disulphide interactions. Hydrophobically driven associations occur within the aggregates.

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