Effect of Alkyl Chain Length on Interfacial Performance of Alkyl Gallates in Supramolecular Oxidation of Soybean Bulk Phase Oil

Abstract

From an interfacial phenomena standpoint, the effect of length of alkyl chain was evaluated on activities of gallic acid and its alkyl ester derivatives in supramolecular oxidation of stripped soybean oil. The gallic acid molecules (log P = -0.47) with an electron-donating carboxylate anion had a higher scavenging activity against DPPH• than alkyl gallates. Interfacial activities of gallates in emulsion and bulk oil improved as the lengths of the alkyl chain were reached until a critical chain length; after that, further chain length extension causes a decrease in potency. In β-carotene bleaching and Rancimat assays higher inhibitory effect was observed for dodecyl and propyl gallate, respectively. Evaluation of interfacial tension, water content, and droplet size of hydroperoxides reverse micelles in parallel with lipid peroxidation indicated that the inhibitory effect of the alkyl gallates, especially methyl gallate, was significantly better than the gallic acid in the bulk phase oil.