Disulfide cleavage to improve interfacial behavior and emulsification properties of oat protein

Abstract

Disulfide bonds play an essential structural role but may hinder the molecular flexibility and functionality of proteins. The present study investigated the effect of disulfide cleavage on emulsifying activity of oat protein isolate (OPI). Four reducing agents tested (dithiothreitol, ascorbic acid, cysteine, and sodium bisulfite) except ascorbic acid disrupted inter-subunit SS bonds of OPI (up to 90 %) in a dose-dependent manner. Emulsification properties were measured specifically on cysteine-modified OPI, and the results showed increased emulsifying activity up to 37 % after subunit dissociation, which exposed hydrophobic groups and loosened the structure. In particular, emulsions formed by cysteine-treated OPI (1.7 to 6.7 mM/mg protein) displayed a superior interfacial protein coverage (0.170 m2/mg compared to 0.092 m2/mg for control) and reduced emulsion particle size (from 4722 to 2238 nm). The application of cysteine as a structure-modifying food additive can broaden the utilization of oat protein in emulsion-based food products.