Diffusion kinetics of ascorbic acid in a glassy matrix of high-methoxy pectin with polydextrose. (February 2016)

• Record Type: Journal Article
• Authors: Panyoyai, Naksit; Bannikova, Anna; Small, Darryl M.; Kasapis, Stefan
• Is Part Of: Food hydrocolloids. Volume 53(2015:Nov.)
• Page Start: 293
• Page End: 302
• Publication Date: 2016-02
• Subjects: High-methoxy pectin -- Polydextrose -- Ascorbic acid -- Glass transition temperature -- Diffusion kinetics; Hydrocolloids -- Periodicals; Food additives -- Periodicals; Colloïdes -- Périodiques; Aliments -- Additifs -- Périodiques; Colloids; Food additives; Periodicals; Electronic journals; 664.06
• DOI: 10.1016/j.foodhyd.2014.07.016
• Languages: English
• ISSNs: 0268-005X

Abstract

Abstract: The relative mobility of ascorbic acid incorporated in a condensed matrix of high-methoxy pectin (HMP) and polydextrose is reported. Physicochemical and structural characterisation of the high-solid systems utilised modulated differential scanning calorimetry, small deformation dynamic oscillation in shear, scanning electron microscopy, Fourier transform infrared spectroscopy and wide angle X-ray diffraction. Theoretical modeling of the thermomechanical measurements demonstrated that the mechanism of free volume governs stress relaxation phenomena of the polymeric system through the process of vitrification yielding the mechanical glass transition temperature. Combination of UV-vis spectrophotometry and a vitamin-dye binding method was employed to follow for 60 min the diffusion process of ascorbic acid from the concentrated HMP/polydextrose matrix to the absolute ethanol phase throughout the temperature range of −30 to 20 °C. A relatively low estimate of activation energy for the diffusion of vitamin C reflects its freedom of mobility and high free volume, as compared to the relaxation of the polymeric system that exhibits strong temperature dependence in the glass transition region. Utilisation of the concept of diffusion coefficient sheds further light into the relationship between free volume of the polymeric system and diffusional mobility of the micronutrient. Graphical abstract: Highlights: The mechanism of vitamin C diffusion in a glassy hydrocolloid matrix is studied. For the first time, free volume theory was combined with Fickian diffusion kinetics. Physics and the rate of vitamin C transport in the glassy matrix are elucidated.