Investigation of the molecular interactions between beta-lactoglobulin and low methoxyl pectin by multi-detection High Performance Size Exclusion Chromatography

摘要

To achieve controlled physiochemical, structural, and consequently, functional properties of interacting systems containing beta-lactoglobulin (beta LG) and commercial standardized low methoxyl pectin (LMP, DE 36.8%), solution conditions were established and studied at the weight ratio of 3:1 (w/w), pH similar to 6.50. Online multi-detection High Performance Size Exclusion Chromatography (HPSEC) was used to characterize the physicochemical properties of the interacting biopolymer fractions in detail. Results showed that upon direct mixing, similar to 6.1% (w/w) of native dimeric PLG molecules formed complexes with LMP molecules of two sizes, namely [M-w] similar to 250 and 55 kDa. The interactions produced complexes of altered shapes and hydrodynamic properties compared to those of beta LG and LMP controls. Heat-induced (80 degrees C,10 min) denaturation of beta LG greatly increased its participation in the complexes as aggregates, to similar to 10.4%, which appear to favor the LMP molecules of higher [M-W]. Pre-heating LMP, however, impeded its binding to beta LG and increased the amount of unbound beta LG as a result. The effect of sucrose on the interactions between beta LG and LMP was also investigated using a set of similarly treated samples but with sucrose removed from LMP. These studies demonstrated that sucrose greatly facilitated the complex formation, notably between the pre-heated beta LG and LMP. The structures of the complexes were found to be less flexible and less open in the presence of sucrose than its absence. It is suggested that sucrose contributed greatly to the stabilization of the heat-induced beta LG aggregates as they interact with LMP through a preferential exclusion mechanism. Published by Elsevier Ltd.