Quantitative determination of α-tocopherol distribution in a tributyrin/Brij 30/water model food emulsion

Until recently, determining the distribution of antioxidants, AOs, between the oil, interfacial and aqueous regions of opaque emulsions has not worked well because the concentrations of AOs in interfacial regions cannot be determined separately from their concentrations in the oil and water phases. However, our novel kinetic method based on the reaction between an arenediazonium ion and vitamin E, or α-tocopherol, provides the first good estimates for the two partition constants that describe α-tocopherol distribution between the oil/interfacial and water/interfacial regions of tributyrin/Brij 30/water emulsions without physical isolation of any phase. The reaction is monitored by a new derivatization method based on trapping unreacted arenediazonium ion as an azo dye and confirmed by linear sweep voltammetry, LSV. The results by both derivatization and LSV methods are in good agreement and show that α  -tocopherol distributes strongly in favor of the interfacial region when the oil is tributyrin, e.g., ca. 90% when the surfactant volume fraction is ΦI=0.01ΦI=0.01. The second-order rate constant for reaction in the interfacial region is also obtained from the results. Our kinetic method provides a robust approach for determining antioxidant distributions in emulsions and should help develop a quantitative interpretation of antioxidant efficiency in emulsions.

Graphical abstractWe have employed a kinetic method to determine the partition constants that describe α-tocopherol distribution between the oil/interfacial and water/interfacial regions of an emulsion without physical isolation of any phase.Figure optionsDownload full-size imageDownload as PowerPoint slide