Dielectric-barrier discharge (DBD) plasma treatment reduces IgG binding capacity of β-lactoglobulin by inducing structural changes

Abstract

The present study investigated the effects of dielectric-barrier-discharge (DBD) plasma treatment (12 kHz, 40 kV) at 1, 2, 3, and 4 min on the reduction of the immunoglobulin G (IgG) binding capacity of β-lactoglobulin (β-LG). The IgG binding capacity of β-LG was reduced by 58.21% following a plasma treatment time of 4 min, as confirmed by western-blot and ELISA analyses. The reduction in IgG binding capacity of β-LG was directly related to a stepwise change in its structure. The initial drop in the IgG binding capacity of β-LG was found to be caused by conformational alteration, free sulfhydryl exposure and cross-linkage of molecules induced by oxidation of NH-/NH₂- functional groups of peptide bonds and of sensitive amino acid residues (Tyr, Trp) as confirmed by SDS-PAGE, surface hydrophobicity and multi-spectroscopic analyses. Plasma treatment of more than 3 min resulted in cleavage of disulfidebonds and fragmentation of β-LG that was confirmed by LC-MS/MS analysis, which resulted a further decline in the IgG binding capacity of β-LG. Plasma treatment therefore has great potential as a substitute treatment for enzymatic hydrolysis for the production of hypoallergenic milk protein-based products.

Keywords: Antigenicity; DBD plasma treatment; IgG binding; β-Lactoglobulin.