Effects of (+)-catechin on a rice bran protein oil-in-water emulsion: Droplet size, zeta-potential, emulsifying properties, and rheological behavior

The aim of this work was to study the stability of oil-in-water emulsions formed by corn oil with rice bran protein and rice bran protein-catechin complexes, at a (+)-catechin concentration of 0.05%–0.25% (w/v). The experimental results showed that the addition of (+)-catechin decreased the α-helix and β-sheet content to 10.15% and 36.68%, respectively. The surface hydrophobicity increased, and the oil-water interfacial tension decreased to 11.52 mN/m. The emulsions using the rice bran protein-catechin complex (0.15%, w/v) showed the smallest droplet size and the best emulsifying properties. However, a (+)-catechin concentration above 0.20% (w/v) negatively affected the emulsion stability, with increasing droplet size and decreasing absolute ζ-potential values due to protein aggregation. Rheological behavior analyses suggested that the rice bran protein-catechin complex emulsion had higher viscosity and viscoelasticity than the emulsion formed with the control rice bran protein.