Dual modification of rice bran protein by enzymatic hydrolysis and tannic acid: Impacts on structural characteristics and emulsifying properties.

Abstract

Rice bran protein (RBP) exhibits limited functional properties because of its compact structure, which reduces its interfacial adsorption capacity and consequently constrains its food applications. This study combined moderate enzymatic hydrolysis and non-covalent complexation with tannic acid (TA) to improve RBP functionality. Moderate hydrolysis combined with TA induced protein unfolding via hydrophobic forces and hydrogen bonding. This effectively enhanced the structural flexibility of RBP and improved its interfacial properties, significantly enhancing its emulsifying and foaming capacity. At a mass ratio of 1:0.2 for TA to rice bran protein hydrolysate (RBPH, at a degree of hydrolysis of 4.39%), the emulsifying activity index (EAI) reached 263.42 ± 5.60 m2/g, and foaming capacity (FC) 205.33 ± 6.25%. The RBPH-TA complexes effectively stabilized oil-in-water emulsions. TA improved emulsion viscoelasticity and inhibited droplet coalescence. This study introduces a viable strategy to improve RBP functionality and offers mechanistic insights into its emulsion stabilization behavior.