Distribution of catechol in emulsions

摘要

In this work, we have evaluated the effects of emulsifier concentration on the distribution of catechol (1,2-dihydroxybenzene, CAT) in food-grade emulsions composed of stripped corn oil, acidic water, and Tween 20. Auxiliary experiments in binary stripped corn oil–water mixtures, in the absence of emulsifier, showed that CAT is both oil and water soluble (partition constant P_W~O = 0.34). Addition of Tween 20 to prepare kinetically stable emulsions creates an interfacial region, and the distribution of CAT is now described by two partition constants, that between the oil and interfacial region, P_O~I, and that between the aqueous and interfacial region, P_W~I. These partition constants were determined in the intact emulsion by employing a kinetic method that exploits the reaction between the hydrophobic 4-hexadecylbenzenediazonium ions, 16-ArN_2~+, and CAT. Results show that CAT distributes between the three regions. At emulsifier volume fractions of Φ_I = 0.005, CAT is predominantly located (~61%) in the aqueous region, about 26% is in the interfacial region, and only a small fraction (~13%) in the oil region. An increase in emulsifier concentration promotes the incorporation of CAT to the interfacial region up to ~70% at Φ_I = 0.037. Results obtained should contribute to a better understanding of the antioxidant efficiency in inhibiting lipid oxidation and to the development of new strategies to prepare healthier and more nutritional foods with longer shelf life.