The influence of various emulsifiers on the partitioning and antioxidant activity of hydroxybenzoic acids and their derivatives in oil-in-water emulsions

The partitioning behavior of a series of hydroxybenzoic acids and their derivatives was determined in biphasic water-oil systems, emulsifier solutions, and oil-in-water (O/W) emulsions. The effect of gradually decreasing polarity on partitioning behavior and antioxidant efficiency in O/W emulsions was investigated by using gallic acid and its esters as antioxidants. Sodium dodecyl sulfate (SDS), cetyltrimethylammbnium bromide (CTAB), polyoxyethylene 20 cetyl ether (Brij 58), and partially hydrolyzed soybean lecithin (PHLC, Emultop(R)) were used to investigate the influence of different classes of emulsifiers on the partitioning behavior. The antioxidant activity of gallic acid and its methyl, ethyl, propyl, butyl, and octyl esters showed markedly different trends in O/W emulsions depending on the emulsifier used. The results are discussed with respect to the properties of the emulsifiers, such as hydrogen bond basicity, hydrophobic interactions, and structural properties.