Using pseudophase models to determine antioxidant distributions in emulsions: why dynamic equilibrium matters

Posted on 23 April, 20172 January, 2019 by antiox@uvigo.es

Distributions of a homologous series of protocatechuic acid (PCA) derivatives of increasing lipophilicity were determined in stripped soybean oil-in-water emulsions and compared with their antioxidant (AO) efficiencies. The distribution was determined by employing a recently developed a kinetic method, based on the reaction between the hydrophobic 4-hexadecylbenzenediazonium ions (16-ArN2+) and the antioxidants [...]

Physical evidence that the variations in the efficiency of homologous series of antioxidants in emulsions are due to differences in their partitioning

Posted on 13 January, 201710 May, 2017 by antiox@uvigo.es

The relationships between the hydrophilic-lipophilic balance (HLB) of antioxidants (AOs) and their distributions and efficiencies in emulsions are not fully understood. Recent reports indicate that, for series of homologous antioxidants of different hydrophobicity, the variation of their efficiency with the HLB of the AO increases with the alkyl chain length up to a maximum (C3 -C8ester) followed by a decrease [...]

A physicochemical study of the effects of acidity on the distribution and antioxidant efficiency of Trolox in olive-oil in water emulsions

Posted on 18 January, 201611 May, 2017 by antiox@uvigo.es

The efficiency of antioxidants to inhibit the oxidation of lipid-based emulsions depends on several factors including their nature and their concentration at the reaction site. Here, we have analyzed the effects of acidity and of surfactant concentration on the distribution and efficiency of the vitamin E analog Trolox (TR) in stripped olive oil-in-water emulsions stabilized with Tween 20 [...]

Interfacial kinetics in octane based emulsions. Effects of surfactant concentration on the reaction between 16-ArN2+ and octyl and lauryl gallates

Posted on 5 September, 201514 May, 2017 by antiox@uvigo.es

Here we have applied the formalism of the pseudophase kinetic model to analyze the reactivity of 4-hexadecylbenzenediazonium, 16-ArN2+, ions with the antioxidants octyl gallate (OG) and lauryl gallate (LG) in emulsions composed of octane, acidic water and hexaetyleneglycol monododecyl ether, C12E6 [...]

Distributions of phenolic acid antioxidants between the interfacial and aqueous regions of corn oil emulsions: effects of acidity and emulsifier concentration

Posted on 17 July, 201514 May, 2017 by antiox@uvigo.es

The oxidative stability of emulsions depends on acidity because pH may affect, among other things, the concentration of antioxidants (AOs) at the reaction site. Here we investigated the effects of pH on the partition constant, PWI, and the distribution of two phenolic acid AOs, gallic (GA) and caffeic (CA), between the aqueous (W) and interfacial (I) regions, in emulsions of 1:9 (vol:vol) corn oil/acidic water [...]

To model chemical reactivity in heterogeneous emulsions: think homogeneous microemulsions

Posted on 25 March, 201514 May, 2017 by antiox@uvigo.es

Two important and unsolved problems in the food industry and also fundamental questions in colloid chemistry are how to measure molecular distributions, especially antioxidants (AOs), and how to model chemical reactivity, including AO efficiency in opaque emulsions. The key to understanding reactivity in organized surfactant media is that reaction mechanisms are consistent with a discrete structures–separate continuous regions duality [...]

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

Posted on 21 January, 201514 May, 2017 by antiox@uvigo.es

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 [...]

Distribution and antioxidant efficiency of resveratrol in stripped corn oil-in water emulsions

Posted on 4 April, 201414 May, 2017 by antiox@uvigo.es

We investigated the effects of resveratrol (RES) on the oxidative stability of emulsions composed of stripped corn oil, acidic water and Tween 20 and determined its distribution in the intact emulsions by employing a well-established kinetic method. The distribution of RES is described by two partition constants, that between the oil-interfacial region, POI, and that between the aqueous and interfacial region, PWI [...]

Distribution of catechol in corn oil emulsions

Posted on 3 April, 201414 May, 2017 by antiox@uvigo.es

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 math formula = 0.34) [...]

Influence of temperature on the distribution of catechin in corn oil-in water emulsions and some relevant thermodynamic parameters

Posted on 25 March, 201414 May, 2017 by antiox@uvigo.es

We investigated the effects of increasing temperature and emulsifier volume fraction (ΦI) on the distribution of catechin (CAT) in stripped corn oil-in-water emulsions. We also estimated relevant thermodynamic parameters for the transfer of CAT from the aqueous to the interfacial region because CAT is sparingly soluble in corn oil and mainly distributes between the aqueous and interfacial regions of emulsions [...]