A Physicochemical Study of the Effects of Acidity on the Distribution and Antioxidant Efficiency of Trolox in Olive Oil-in-Water Emulsions

The efficiency of antioxidants to inhibit the oxidation of lipid‐based emulsions depends on several factors including their nature and their concentration at the reaction site. Here, we have analyzed the effects of acidity and of surfactant concentration on the distribution and efficiency of the vitamin E analog Trolox (TR) in stripped olive oil‐in‐water emulsions stabilized with Tween 20. The distribution was assessed in the intact emulsions by employing a kinetic method that exploits the reaction between the hydrophobic 4‐hexadecylbenzenediazonium ions and TR. Kinetic results are interpreted on the grounds of the pseudophase model. The effects of TR on the oxidative stability of the emulsion were determined at different pH values by monitoring the formation of conjugated dienes over time. The results show that the efficiency of TR increases upon increasing pH even though its concentration in the interfacial region decreases. Oil and water: The effects of acidity and of surfactant concentration on the distribution and efficiency of the antioxidant Trolox in oil‐in‐water emulsion were analyzed. Trolox is shown to mainly distribute between the aqueous and interfacial regions (pH dependent) even though it is oil soluble.