The effect of moisture content on the crystallinity and glass transition temperature of inulin

This paper focuses on the physicochemical characterization of inulin, an important fractooligosaccharide with dietary fiber properties, and its dependence on water sorption properties. The moisture sorption isotherm of inulin was determined at 25degreesC and fitted to the GAB model. Inulin's glass transition temperature (T-g) was measured by differential scanning calorimetry (DSC) as a function of water content; the Gordon-Taylor equation was used to fit the experimental data. Relative crystallinity of inulin was determined by X-ray diffraction and DSC studies, Native inulin was found to be a semi-crystal line material, which, at 25degreesC and storage water activity values below 0.75, was found in a glassy state. When pre-solubilized, inulin's relative crystallinity depended on moisture content: crystallinity was low at low moist-are contents, while, at water activities above 0.75 (conditions above T-g), it recrystallized and reached native inulin's crystallinity level. (C) 2002 Elsevier Science Ltd. All rights reserved.