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Sorption isotherm and state diagram for indica rice starch with and without soluble dietary fiber

Wan, Jie, Ding, Yueping, Zhou, Guohui, Luo, Shunjing, Liu, Chengmei, Liu, Fei
Journal of cereal science 2018 v.80 pp. 44-49
dietary fiber, drying, freezing, glass transition, glass transition temperature, gravimetry, models, rice, rice starch, sorption isotherms, storage quality
Moisture sorption isotherms and state diagrams for indica rice starch (IRS) and indica rice starch-soluble dietary fiber (IRS-SDF) were developed to investigate the effect of SDF on the stability of IRS. Sorption isotherms of IRS and IRS-SDF were determined by the static gravimetric method and the data were modeled by Guggenheim–Anderson–de Boer (GAB) model. The GAB monolayer moisture contents were calculated to be 7.43 and 8.37 g/100g (dry basis) for IRS and IRS-SDF, respectively. The state diagram was composed of the glass transition line and freezing curve, which were fitted according to Gordon–Taylor and Chen models, respectively. The ultimate maximum-freeze-concentration conditions were calculated as characteristic glass transition temperature (Tg’) of −42.5 °C and −31.5 °C with characteristic solids content (Xs') being 0.71 and 0.72 g/g (wet basis), and characteristic temperature of end point of freezing (Tm’) being −18.2 °C and −13.8 °C for IRS and IRS-SDF, respectively. The state diagrams and sorption isotherms of IRS and IRS-SDF have great significance for evaluating storage stability, optimizing drying and freezing processes.