Enhancing Effect of β-Lactoglobulin on the Antioxidative Activity of α-Tocopherol in an Emulsion of Linoleic Acid.

Abstract

The antioxidative activity of α-tocopherol and Trolox, a water-soluble carboxylic acid derivative of α-tocopherol, in an emulsion stabilized with the hydrophilic emulsifier, polyoxyethylene (20) sorbitan monolaurate, was evaluated by measuring the changes in linoleic acid content, peroxide value, and thiobarbituric acid value. The activity of α-tocopherol and Trolox to depress the autoxidation of linoleic acid was stronger when they were added in the aqueous phase than when added in the oil phase, and Trolox in the aqueous phase was the most effective. The results of interfacial-tension measurements support the idea that the affinity of phenolic antioxidants to the surface layer of oil droplets might be related to their antioxidative activity. The antioxidative activity of α-tocopherol and Trolox added in the oil phase was markedly enhanced by using β-lactoglobulin together with Tween 20 to stabilize a linoleic acid emulsion. The results of a linoleic acid determination with cold and radioactive linoleic acid indicate that linoleic acid in a complex with the β-lactoglobulin molecule would be effectively protected by the phenolic antioxidants, α-tocopherol and Trolox, against autoxidation.