Issue 3, 2015

Transfer of antioxidants at the interfaces of model food emulsions: distributions and thermodynamic parameters

Abstract

Knowledge on the driving force for the hydrophobic effect that partitions antioxidants (AOs) between the oil (O), aqueous (W) and interfacial (I) regions of food emulsions is crucial to predict their efficiency in inhibiting lipid oxidation and to preserve the organoleptic properties of lipid-based foods. Here, we have investigated the effects of temperature and surfactant volume fraction (ΦI) on the distribution of two representative AOs, the water insoluble α-tocopherol (TOC) and the oil insoluble caffeic acid (CA), in a model food emulsion composed of stripped corn oil, acidic water and the nonionic surfactant Tween 20. The distribution of the AOs is assessed in the intact emulsions by employing a well-established kinetic method based on the reaction between a hydrophobic arenediazonium ion and the AOs. The variations of the observed rate constant, kobs, with ΦI are interpreted on the grounds of the pseudophase kinetic model, which provides values for the interfacial rate constant kI and the partition constants between the aqueous–interfacial (PIW) and oil–interfacial (PIO) regions of the emulsions. From the variations of PIW, PIO and kI at a series of temperatures, we determined the Gibbs free energy, enthalpy and entropy values for the transfer of CA from the water to the interfacial (W → I) region and of TOC from the oil to the interfacial (O → I) regions of the emulsions, and the activation parameters for the reaction in the interfacial region. Activation energy values are in line with those expected for a bimolecular reaction. Results show that the W → I and O → I transfer processes are spontaneous and entropy driven.

Graphical abstract: Transfer of antioxidants at the interfaces of model food emulsions: distributions and thermodynamic parameters

Supplementary files

Article information

Article type
Paper
Submitted
27 sep 2014
Accepted
30 okt 2014
First published
30 okt 2014

Org. Biomol. Chem., 2015,13, 876-885

Transfer of antioxidants at the interfaces of model food emulsions: distributions and thermodynamic parameters

S. Losada-Barreiro, V. Sánchez-Paz and C. Bravo-Díaz, Org. Biomol. Chem., 2015, 13, 876 DOI: 10.1039/C4OB02058H

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