The influence of bovine serum albumin on β-lactoglobulin denaturation, aggregation and gelation

The effect of bovine serum albumin (BSA) on the heat-induced denaturation, aggregation and subsequent acid-induced gelation of beta-lactoglobulin (beta-lg) was investigated in this work. Changes in the denaturation kinetics of beta-lg during heating at 78 degrees C were determined by monitoring the disappearance of the native protein by reverse-phase chromatography. Replacing beta-lg with increasing amounts of BSA, while keeping the total protein concentration constant at 5% (w/w), significantly increased the denaturation rate of beta-lg from 2.57 +/- 0.30x10(-3) (g L-1)((1-n)s-1) to 5.07 +/- 0.72x10(-3) (g L-1)((1-n)s-1) (beta-lg: BSA ratio of 3:1 w/w). The reaction order for beta-lg was 1.40++/- 0.09. Partial replacement of beta-lg with BSA (beta-lg: BSA ratio of 3:1 w/w) significantly increased the reaction order to 1.67 +/- 0.13. Heat-induced aggregates between beta-lg and BSA were studied by dynamic light scattering, two-dimensional electrophoresis and size exclusion chromatography. The partial replacement of beta-lg with BSA significantly changed the gelling properties of the acid-induced gels. A rapid rate of acidification resulted in a significant decrease, while a slow acidification rate resulted in a significant increase in gel strength. Size exclusion chromatography demonstrated that intermolecular disulphide bond formation occurred during both heat-induced denaturation/aggregation and subsequent acid-induced gelation. Results clearly indicate that BSA contributed to the formation of these disulphide bonds. (C) 2006 Elsevier Ltd. All rights reserved.