Enhancing the fraction of antioxidants at the interfaces of oil-in-water emulsions: A kinetic and thermodynamic analysis of their partitioning.

The distribution of antioxidants (AOs) in O/W emulsions depends on two partition constants, that between oil-interfacial (P_O^I), and that between the aqueous-interfacial (P_W^I) regions, that need to be determined in the unbroken emulsion to prevent disruptions of the present equilibria. Prediction of the effects of temperature on AO partitioning is challenging because may change both P_O^I and P_W^I in a different extent and the control of their interfacial concentrations is crucial to optimize their antioxidant efficiency. Such effects can be analyzed in the intact emulsions with the aid of a pseudophase kinetic model.

Here we estimated the partition constants of the food-grade antioxidants -propyl (PG), octyl (OG) and lauryl (LG) gallates- in intact corn oil-in-water emulsions and their interfacial concentrations by employing a kinetic methods, and carried out a thermodynamic analysis of the transfer parameters controlling their partitioning.Results show that the Gibbs free energy for the transfer of gallates to the interfacial region is spontaneous and the transfer process is enthalpy driven. An increase in T favors their incorporation into the interfacial region in an extent that depends on AO hydrophobicity. For any of AOs, the effective interfacial concentrations are much higher (15-170 fold) than the stoichiometric concentration. Results are basic to get a deeper knowledge on the driving force that partitions the AOs in lipid-based foods and to select the best AO to minimize the oxidation of lipids.