Inhibition of Lipid and Protein Oxidation in Whey-Protein-Stabilized Emulsions Using a Natural Antioxidant: Black Rice Anthocyanins

The food industry is exploring the natural environment to identify botanical extracts that can be used as functional ingredients that can replace synthetic ingredients in foods. In the present study, the ability of black rice anthocyanins as natural antioxidants to inhibit both lipid and protein oxidation in protein-stabilized oil-in-water emulsions was examined. Whey-protein-stabilized emulsions were prepared containing 0, 0.02, 0.04, and 0.06% (w/v) anthocyanins, and then the impact of this plant-based extract on their physical and chemical stabilities was evaluated. The addition of the anthocyanins improved the physical stability of the emulsions in a dose-dependent manner by inhibiting droplet aggregation during storage (35 °C for 5 days). The anthocyanins also exhibited good antioxidant activity in a dose-dependent manner, as seen by their capacity for inhibiting both lipid oxidation (reduced lipid hydroperoxides and malondialdehyde) and protein oxidation (reduced carbonyl and Schiff base formation, intrinsic fluorescence loss, and molecular weight changes). Black rice anthocyanins may therefore be an effective botanical extract for improving the stability of protein-stabilized food emulsions by inhibiting oxidative reactions.