Interfacial Concentrations of Hydroxytyrosol and Its Lipophilic Esters in Intact Olive Oil-in-Water Emulsions: Effects of Antioxidant Hydrophobicity, Surfactant Concentration, and the Oil-to-Water Ratio on the Oxidative Stability of the Emulsions

Almeida, Joao Pedro; Losada‐Barreiro, Sonia; Costa, Marlene; Paiva‐Martins, Fátima; Romsted, Laurence S.

doi:10.1021/acs.jafc.6b01468

Cited by 65 publications

(120 citation statements)

References 46 publications

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“…In accordance with our previous work, the distribution results show that the nonlinear effect of the hydrophobicity of chlorogenates on their AO activity in emulsions is due to their differential affinities towards the interfacial region.…”

Section: Discussionsupporting

confidence: 92%

“…. This emulsifier concentration effect in the variation of %AO I for chlorogenates has already been observed for other series of homologous AOs in different O/W ratios, where the importance of the emulsifier concentration in controlling the AOs concentration at the reaction site was demonstrated and highlighted …”

Section: Resultssupporting

confidence: 73%

“…The efficiency does not correlate with the hydrophobicity of AOs, increasing with increasing length of the alkyl chain to a maximum, after which a decrease is observed. This phenomenological, parabola‐like, variation of the efficiency is the so‐called ‘cut‐off’ effect already reported by us and others for several series of homologous AOs bearing the same reactive moiety but different hydrophobicities. Our results are also qualitatively similar to those reported by Laguerre et al in Brij 35 stabilized sunflower oil‐in water emulsions …”

Section: Resultssupporting

confidence: 65%

“…By employing a pseudophase kinetic model, we were able to determine the distribution of a series of AOs derived from hydroxytyrosol in intact oil‐in‐water emulsions and demonstrated that there is a direct relationship between the efficiency of AOs and the percentage of AO in the interfacial region of the emulsion (Fig. (A)) . This fundamental result implies that the efficiency of AOs can, in principle, be increased by fine‐tuning their hydrophobicity to achieve the maximum interfacial concentrations.…”

Section: Introductionmentioning

confidence: 91%

“…(A) Variation of the time to reach 0.5% conjugated dienes (CDs) and the values of the percentages of AOs in the interfacial region of 4 : 6 ( O/W) olive oil‐in‐water emulsions, %AO I , with the number of carbon atoms at Φ I = 0.01 for a series of hydroxytyrosol esters. Extracted from Almeida et al (B) Variation of %AO I of 4 : 6 (O/W) olive oil‐in‐water emulsions showing the nonlinear variation of %AO I with the hydrophobicity of the AOs ( caffeates; hydroxytyrosol esters; gallates) …”

Section: Introductionmentioning

confidence: 99%

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Control of antioxidant efficiency of chlorogenates in emulsions: modulation of antioxidant interfacial concentrations

et al. 2019

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BACKGROUND Controlling the interfacial concentrations of antioxidants (AOs) in oil‐in‐water emulsions can be regarded as a unique approach for increasing the efficiency of AOs in inhibiting the oxidation of lipids. Classical methods to determine the AO distribution in binary systems cannot be employed and their distribution needs to be assessed in the intact emulsion. RESULTS We have employed a well‐established kinetic method to determine the distribution of a homologous series of AOs derived of chlorogenic acid in olive oil‐in‐water emulsions and analyse the effects of AO hydrophobicity on their distributions and their efficiencies. Results indicate that variations in the efficiency of chlorogenates in emulsions are due to differences in their interfacial concentrations. Their interfacial concentrations AOI were much higher (20‐ to 150‐fold) than their stoichiometric concentrations. On the other hand, their concentrations in the oil region were 1.5‐ to 0.1‐fold. Results also show the complex effect of the oil‐to‐water ratio employed in the preparation of the emulsions on the (AOI) values. CONCLUSION Results highlight the key role of the interfacial region and of its composition (interfacial AO molarity, emulsifier concentration, oil‐to‐water ratio) in interpreting the efficiency of AOs in inhibiting lipid oxidation in emulsions. Thus, a careful modulation of these parameters is necessary to ensure optimum AO efficiency. © 2019 Society of Chemical Industry

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Section: Discussionsupporting

confidence: 92%

Section: Resultssupporting

confidence: 73%

Section: Resultssupporting

confidence: 65%

Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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Control of antioxidant efficiency of chlorogenates in emulsions: modulation of antioxidant interfacial concentrations

et al. 2019

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Partitioning and antioxidative effect of protocatechuates in soybean oil emulsions: Relevance of emulsifier concentration

Silva

Losada‐Barreiro

Paiva‐Martins

et al. 2017

Euro J Lipid Sci & Tech

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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, that allows to determine the partition constants between the oil‐interfacial, PnormalOnormalI, and water‐interfacial, PnormalWnormalI, regions of the emulsion and their interfacial molarities. Our results show that: (i) at low surfactant volume fractions, ΦI = 0.005, a significant fraction (>50%) of all protocatechuates is located in the interfacial region of soybean oil emulsions. The percentage increases with increasing ΦI such that at ΦI = 0.04, than 90% of the AOs are located in the interfacial region; (ii) the variation of the hydrophobicity of the AOs has a modest effect on their concentration in the interfacial region, particularly at ΦI > 0.01, and an almost negligible effect on their antioxidant efficiency in the same emulsions; (iii) a positive correlation between the antioxidant efficiency and the interfacial molarities of the protecatechuates was established. Practical application: Results will contribute to a deeper understanding of oxidative stability in polyunsaturated acids enriched emulsions, will enhance current understanding of how AO structure and physical location within the food system affect their efficiency and will provide basic information on the factors controlling AO distributions and efficiencies, allowing a more rational selection of AOs in food stabilization. The outcome of this research will help the development of more efficient antioxidant strategies for food preservation and for the oxidative protection of nutritionally important bioactive lipids. There is a positive correlation between the antioxidant efficiency of protocatechuates of different HLB and their interfacial concentration, (AOI), in soybean oil emulsions.

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Using a pseudophase model to determine AO distributions in emulsions: Why dynamic equilibrium matters

Bravo‐Díaz

Romsted

Paiva‐Martins

2017

Euro J Lipid Sci & Tech

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For decades, explorations with ground state, thermal reactions combined with pseudophase kinetic models and methods for interpreting the results have provided insights into the properties of the different regions of homogeneous association colloids. More recent successful determination of antioxidant (AO) distributions by this approach is providing new insights into AO efficiency in opaque, well‐mixed two‐phase intact emulsions and eliminating the need to separate the phases. The chemical probe reacts with AOs exclusively in the interfacial region of the emulsion, permitting simplification of the kinetic treatment, and determining its distribution between the oil, interfacial, and aqueous regions. AO distributions are obtained from the two partition constants, PnormalOnormalI and PnormalWnormalI, of the AOs between the oil‐interfacial and aqueous‐interfacial regions, respectively. PnormalOnormalI and PnormalWnormalI values are obtained by fitting the observed rate constant, kobs, versus surfactant concentration profiles with an overall kinetic approach or model we call the “pseudophase chemical kinetic method.” However, because emulsions break up and reform, and reactants and other components diffuse at various time scales within and between the oil, interfacial, and water regions, kobs could also depend on reactant diffusion coefficients. Here we demonstrate that reactant diffusion is generally orders of magnitude faster than most thermal reactions and reactant distributions between the multiple oil, aqueous, and interfacial droplets and regions of emulsions are in dynamic equilibrium throughout the multiphase systems during the time course of the reaction. Thus, kinetic probes are powerful tools for determining structure‐reactivity, for example, the HLB, relationships governing AO distributions and efficiencies in emulsions. Practical applications: The analysis presented here demonstrates that one of the basic assumptions of the pseudophase chemical kinetic model that we have developed has a solid foundation in the properties of emulsions. That is, we can determine the distributions of reactants between oil (O), interfacial (I), and aqueous (W) regions of the emulsions because the diffusivity coefficients of reactants within emulsions are orders of magnitude greater than the rate of the reaction between the antioxidant and the 4‐hexadecylbenzenediazonium probe. Consequently, we can use the same kinetic model in emulsions as we have used in homogeneous microemulsions. The method permits determination of the partition constants of many antioxidants between the O‐I and W‐I regions of the emulsions and from them their distributions. The method provides new insights into the relationships between antioxidant hydrophobic‐lipophilic balance (HLB) and its efficiency in emulsions and a natural explanation for the cut‐off effect observed with increasing antioxidant HLB. Interpreting chemical reactivity in emulsions requires that reactive components A and B be in dynamic equilibrium, that separate second order rate consta...

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Interfacial Concentrations of Hydroxytyrosol and Its Lipophilic Esters in Intact Olive Oil-in-Water Emulsions: Effects of Antioxidant Hydrophobicity, Surfactant Concentration, and the Oil-to-Water Ratio on the Oxidative Stability of the Emulsions

Cited by 65 publications

References 46 publications

Control of antioxidant efficiency of chlorogenates in emulsions: modulation of antioxidant interfacial concentrations

Control of antioxidant efficiency of chlorogenates in emulsions: modulation of antioxidant interfacial concentrations

Partitioning and antioxidative effect of protocatechuates in soybean oil emulsions: Relevance of emulsifier concentration

Using a pseudophase model to determine AO distributions in emulsions: Why dynamic equilibrium matters

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