Determining Antioxidant Distributions in Intact Emulsions by Kinetic Methods: Application of Pseudophase Models

Romsted, Laurence S.; Bravo‐Díaz, Carlos

doi:10.1007/978-3-030-87222-9_2

Cited by 7 publications

(33 citation statements)

References 54 publications

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“…By applying the formalism of the pseudophase model (described in detail elsewhere) [ 21 , 30 , 74 ], Equation (5) can be derived.

…”

Section: Resultsmentioning

confidence: 99%

“…Equation (6) is the reciprocal of Equation (5), and it predicts that plots of 1/ k obs vs. Φ I should be linear with positive intercepts, where the values of the partition constants are obtained from the ratio between the slope and the intercept. Details on the procedure can be found elsewhere [ 21 , 30 , 74 ].…”

Section: Resultsmentioning

confidence: 99%

“…The reaction between 16-ArN 2 + and antioxidants was monitored spectrometrically using a batch method, as described in detail elsewhere [ 30 , 71 , 72 , 73 ]. Because emulsions are opaque, a special protocol, described in detail elsewhere [ 21 , 30 , 74 ], was employed to monitor reactions in the intact emulsions. Briefly, the protocol exploits the rapid reaction of the chemical probe (16-ArN 2 + ions) with a proper coupling agent, such as N-(1-naphthyl)ethylenediamine, NED, to yield a stable azo dye.…”

Section: Methodsmentioning

confidence: 99%

“…The optimal location of the antioxidants in emulsions is in the interface of emulsions, where the inhibition reaction between the antioxidants and peroxyl radicals takes place as a result of their massive accumulation in the region [ 7 , 74 , 76 ]. The efficiency of antioxidants depends on their chemical structure, that is, on the number and location of -OH groups, double bonds, and side-chain substituents, which affects its intrinsic ability to scavenge peroxyl radicals.…”

Section: Conclusion and Final Remarksmentioning

confidence: 99%

“…The efficiency of antioxidants depends on their chemical structure, that is, on the number and location of -OH groups, double bonds, and side-chain substituents, which affects its intrinsic ability to scavenge peroxyl radicals. However, in addition to this scavenging ability, the different substituents also affect their relative hydrophobicity/hydrophilicity, resulting in a differential distribution of the antioxidants within the various regions of the emulsions [ 74 ] and its probable orientation in the interface [ 76 ].…”

Section: Conclusion and Final Remarksmentioning

confidence: 99%

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Distributions of α- and δ-TOCopherol in Intact Olive and Soybean Oil-in-Water Emulsions at Various Acidities: A Test of the Sensitivity of the Pseudophase Kinetic Model

et al. 2022

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During the last years, the formalism of the pseudophase kinetic model (PKM) has been successfully applied to determine the distributions of antioxidants and their effective interfacial concentrations, and to assess the relative importance of emulsion and antioxidant properties (oil and surfactant nature, temperature, acidity, chemical structure, hydrophilic-liphophilic balance (HLB), etc.) on their efficiency in intact lipid-based emulsions. The PKM permits separating the contributions of the medium and of the concentration to the overall rate of the reaction. In this paper, we report the results of a specifically designed experiment to further test the suitability of the PKM to evaluate the distributions of antioxidants among the various regions of intact lipid-based emulsions and provide insights into their chemical reactivity in multiphasic systems. For this purpose, we employed the antioxidants α- and δ-TOCopherol (α- and δ-TOC, respectively) and determined, at different acidities well below their pKa, the interfacial rate constants kI for the reaction between 16-ArN2+ and α- and δ-TOC, and the antioxidant distributions in intact emulsions prepared with olive and soybean oils. Results show that the effective interfacial concentration of δ-TOC is higher than that of α-TOC in 1:9 (v/v) soybean and 1:9 olive oil emulsions. The effective interfacial concentrations of tocopherols are much higher (15-96-fold) than the stoichiometric concentrations, as the effective interfacial concentrations of both δ-TOC and α-TOC in soybean oil emulsions are higher (2-fold) than those in olive oil emulsions. Overall, the results demonstrate that the PKM grants an effective separation of the medium and concentration effects, demonstrating that the PKM constitutes a powerful non-destructive tool to determine antioxidant concentrations in intact emulsions and to assess the effects of various factors affecting them.

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“…By applying the formalism of the pseudophase model (described in detail elsewhere) [ 21 , 30 , 74 ], Equation (5) can be derived.

…”

Section: Resultsmentioning

confidence: 99%