Evaluation of antioxidant–surfactant interactions using size distribution Taylor dispersion analysis: measuring antioxidant partitioning and size of native-state micelles

In food emulsions, excess surfactants often lead to the formation of micelles, which play a critical role in modulating the localization and efficacy of antioxidants. The interactions between antioxidants and micelles can either enhance or impair antioxidant function. Despite this importance, methodologies to study these interactions in native-state micelles remain limited. In this study, we employed Size Distribution - Taylor Dispersion Analysis (SD-TDA), a fast and absolute technique for measuring diffusion coefficients and thus hydrodynamic radii, to investigate antioxidant-surfactant interactions in sodium dodecyl sulfate (SDS) micelles, both below and above its critical micelle concentration. Studied antioxidants include α-tocopherol, curcumin, gallic acid, propyl gallate, and octyl gallate. The results revealed distinct behaviors: while gallic acid remained in the aqueous phase regardless of SDS presence, octyl gallate appeared to co-micellize with SDS. Curcumin was fully incorporated into SDS micelles, with micelle size increasing from 4.68 ± 1.52 nm to 6.92 ± 0.79 nm at the maximum loading capacity of 3.57 ± 0.05 mM curcumin with 20 mM SDS. α-Tocopherol also localized within SDS micelles; however, above 2.5 mM, three distinct populations were identified using SD-TDA-free tocopherol in water, tocopherol in small micelles, and swollen SDS micelles. Unlike Dynamic Light Scattering, SD-TDA successfully resolved these populations and provided quantitative insights into their size and α-tocopherol partitioning. These findings highlight the potential of SD-TDA as a powerful tool for studying antioxidant partitioning and micellar interactions, opening the way for more in-depth investigations into the role of micelles in antioxidant efficiency in emulsified systems.