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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 O W = 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 I O , and that between the aqueous and interfacial region, P I W . 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.

Isobaric vapor-liquid equilibria are measured for 1-hexene + o-xylene, + m-xylene, + p-xylene, + toluene, and + ethylbenzene at 101.3 kPa, using a dynamic still with circulation in both of the phases. The experimental data are tested for thermodynamic consistency and could be represented well by the Wilson and UNIQUAC equations, with the latter being far better. A comparative analysis of the application of the group contribution methods ASOG, original UNIFAC, modified UNIFAC-Dortmund, and modified UNIFAC-Lyngby to the mixtures of this study showed that UNIFAC-Lyngby gives better results.

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