Differences in antioxidant activity between two rice protein concentrates in an oil‐in‐water emulsion

Two formulations of rice protein concentrates (RPC) derived from brown rice were evaluated for their antioxidant activity in bulk oil and in oil-in-water emulsions. Bulk oils were mixed with RPC and heated to 180°C, and total polar compounds and triacylglycerol polymerization were measured. Minimal antioxidant activity was observed in the bulk oil phase. Rice protein concentrates were incorporated into soybean oil-in-water emulsions, which were oxidized at 50°C for 8 days. Lipid oxidation in emulsions was assessed via peroxide values (PV), headspace oxygen levels, headspace volatile oxidation products, and fatty acid analysis. One of the RPC treatments showed some antioxidant activity in emulsions, suggesting that RPC could potentially be used to extend shelf life and preserve product quality. Practical applications: Naturally derived antioxidants that can inhibit oxidation in edible oils are in high demand. As consumers become more label-conscious, synthetic antioxidants are falling out of favor. Rice proteins offer a means of antioxidant capability in emulsions, which may have applications in improving shelf life and/or product quality in a variety of foods, including sauces, salad dressings, and dairy products. Rice protein concentrations show more promise in emulsions than in bulk oil. Protein concentrates derived from brown rice (left) were incorporated into oil-in-water emulsions (center) and showed differing abilities to suppress lipid oxidation (linolenic acid, shown right).