Water sorption isotherms for vacuum‐dried persimmon pulp (PP) powder were determined in the temperature range of 20–50C, and the effects of maltodextrin (MD) or gum arabic (GA) addition on the water sorption behavior of the dried powders were analyzed. Several models were evaluated to fit the experimental data and the Guggenheim‐Anderson‐de Boer model was selected as the most adequate to describe the observed behavior. Addition of encapsulants affected the isotherms: at the same water activity, PP powder with added GA (PP + GA) or MD (PP + MD) presented lower equilibrium water content than pure PP and were less affected by temperature variations. Samples of PP + MD presented lower equilibrium moisture content than those of PP + GA. The isosteric heats of sorption of pulp powders with encapsulants were higher (less negative) than those of PP, suggesting that there are more active polar sites in PP than in pulp powder containing encapsulants. PRACTICAL APPLICATIONS The choice of persimmon to carry out this work was due to the large persimmon production available in Brazil; moreover, persimmon pulp is rich in vitamin C, vitamin A and iron, as well as in phenolic compounds. Drying of fruit pulps with high sugar content presents technical difficulties because the hygroscopicity and thermoplasticity of the resulting powders when exposed to high temperature and relative humidity. For this reason, addition of high‐molar‐mass biopolymers, such as maltodextrin or gum arabic, is a strategy to aid drying and to improve storage stability. Knowledge of water sorption isotherms and net isosteric heats of sorption is important to various food processing operations, including drying, storage and packaging. They are useful in calculating time and energy consumptions during drying, modeling moisture changes during storage and predicting shelf life of food products.

Sodium Thiosulphate, Polymorphism, Solid ElectrolyteNa2S2C>3 crystallizes in 4 modifications. The familiar monoclinic a-form stable at ambient temperature transforms into the trigonal /3-form at 330 °C which at 388 °C converts to bcc y-Na2S203. These transformations are reversible. Unstable orthorhombic a'-Na2S2C>3(Pna 2i) is obtained by dehydration of the pentahydrate or by cooling the ß-phase.The y-phase decomposes in sealed ampoule to Na2SC>4 and NaSs; decomposition is slow below and rapid above 440 °C. Equilibrium displacement by distillation of sulphur accelerates decomposition even for /?-Na2S203, and maintaining low sulphur pressure by pumping gives Na2S03. ß-and y-Na2S2C>3 are superionic conductors; a dynamic model is presented for the /3-structure with Na+ conduction pathways originating from oscillation of the S0O3 2-tetrahedra. Structural relationships can be derived with respect to the arrangement of the thiosulphate groups.

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