Tocopheryl acetate release from microcapsules of waxy maize starch

• Published in: Carbohydrate polymers Vol. 167; pp. 27 - 35
• Main Authors: Panyoyai, Naksit, Shanks, Robert A., Kasapis, Stefan
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2017
• Subjects: Diffusional mobility; Glass transition temperature; Molecular coupling parameter; Tocopheryl acetate; Waxy maize starch; Molecular coupling parameter; Diffusional mobility; Waxy maize starch; Glass transition temperature; Tocopheryl acetate
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2017.03.005

•The mechanism of tocopheryl acetate diffusion in waxy maize starch capsules is studied.•For the first time, free volume theory was combined with Fickian diffusion kinetics.•Physics and the rate of tocopheryl acetate transport in starch capsules are elucidated. Diffusion coefficients are utilised to provide a realistic approach in the quantification of mass transport phenomena, which are important for the delivery of bioactivity from high-solid biopolymer systems. Following this mechanistic consideration, we employ spray drying to produce microcapsules of waxy maize starch that suspend homogeneously tocopheryl acetate. An array of physicochemical techniques including dynamic oscillation in-shear or compression mode, microDSC, WAXD, FTIR, scanning electron or optical microscopy, and UV–vis assays were utilised to relate structural properties of the macromolecular network to diffusivity of the bioactive compound. A modified version of the free-volume theory designed to address molecular diffusion was evaluated over a wide temperature range. Predictive capabilities were facilitated by proposing a mathematical relationship between diffusion coefficient of tocopheryl acetate and fractional free volume of waxy maize starch. Moreover, the theoretical approach is able to accurately describe the extent of cooperativity in the vitamin–biopolymer interaction that determines transport kinetics.