Etiqueta: emulsions

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

Publicada en por 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 [...]

Optimizing the efficiency of antioxidants in emulsions by lipophilization:tuning interfacial concentrations

Publicada en por antiox@uvigo.es

Optimization of the efficiency of antioxidants, AOs, in lipid-based emulsions via chemical modifications of their reactive moieties is not always possible because of the inherent experimental difficulties and because of the regulatory status of AOs. Esterification of hydrophilic AOs may be a practical, convenient, alternative approach [...]

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

Publicada en por 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

Publicada en por 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

Publicada en por 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 [...]

A direct correlation between the antioxidant efficiencies of caffeic acid and its alkyl esters and their concentrations in the interfacial region of olive oil emulsions. The pseudophase model interpretation of the “cut-off” effect

Publicada en por antiox@uvigo.es

Recently published results for a series of homologous antioxidants, AOs, of increasing alkyl chain length show a maximum in AO efficiency followed by a significant decrease for the more hydrophobic AOs, typically called the "cut-off" effect. Here we demonstrate that in olive oil emulsions both antioxidant efficiencies [...]

To model chemical reactivity in heterogeneous emulsions: think homogeneous microemulsions

Publicada en por 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

Publicada en por 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 [...]

Effects of acidity, temperature and emulsifier concentration on the distribution of caffeic acid in stripped corn and olive oil in water emulsions

Publicada en por antiox@uvigo.es

We evaluated the effects of oil type, oil to water ratio, emulsifier concentration, acidity, and temperature on the distribution of caffeic acid, CA, in emulsions composed of stripped olive and corn oils, acidic water, and Tween 20. CA mainly distributes between the water and interfacial regions because it is sparingly soluble in oils, as demonstrated by auxiliary partitioning experiments in the absence of an emulsifier [...]

Maxima in antioxidant distributions and efficiencies with increasing hydrophobicity of gallic acid and its alkyl esters. The pseudophase model interpretation of the “cutoff effect”

Publicada en por antiox@uvigo.es

Antioxidant (AO) efficiencies are reported to go through maxima with increasing chain length (hydrophobicity) in emulsions. The so-called “cutoff” after the maxima, indicating a decrease in efficiency, remains unexplained. This paper shows, for gallic acid (GA) and propyl, octyl, and lauryl gallates (PG, OG, and LG, respectively) [...]