Antioxidant Effects of Berry Phenolics Incorporated in Oil‐in‐Water Emulsions with Continuous Phase β‐Lactoglobulin

Abstract The purpose of this study was to evaluate the effects of berry phenolics, in this case, black currant ( Ribes nigrum ) anthocyanins and raspberry ( Rubus idaeus ) ellagitannins, in the presence of continuous phase β‐lactoglobulin (β‐Lg), on the oxidative stability of Brij 35‐stabilized corn oil‐in‐water emulsions. The extent of lipid oxidation in emulsions was measured by determining the formation of lipid hydroperoxides and hexanal, and extent of protein oxidation by monitoring the loss of tryptophan and cysteine residues in the continuous phase β‐Lg. Berry phenolics at concentration levels of 20 and 50 μM were able to prevent lipid oxidation with and without β‐Lg in the aqueous phase. The results show that a combination of β‐Lg and berry phenolics was more efficient in inhibiting hexanal formation than either component alone. Synergistic effects on antioxidant activity toward hexanal were observed only at the 20 μM levels of berry phenolics in combination with continuous phase β‐Lg. The berry phenolics were also able to inhibit the oxidation of tryptophan and cysteine residues of β‐Lg. The results show that the amino acid residues were oxidized prior to the propagation of lipid oxidation. This suggests that these amino acids were able to inhibit fatty acid scission. The information gained from this study would be useful in protecting emulsion‐based food products from oxidative deterioration.