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The influence of polydextrose or plant proteins blend, as a drying aid in freeze-dried açaí pulp, was evaluated regarding stability by vapor sorption isotherms at 20 °C in a water activity range of 0.1–0.95, obtained by vapor sorption analyzer and by saturated salt solutions, and the enthalpic properties were obtained by differential scanning calorimetry. The experimental isotherms data presented a good fit to the Peleg and Guggenheim-Anderson-de Boer (GAB) equations, açaí powder with polydextrose presented a Brunauer-Emmett-Teller (BET) type III, while the açaí powder without and with a plant proteins blend, type II. The freeze-dried açaí powders showed two endothermic peaks between −15 °C and 10 °C, probably related to linoleic and oleic fatty acids fusion. Fusion enthalpies of these peaks were lower when a carrier agent was used, which could be explained by a lower lipids content (25.0 J/g and 3.5 J/g for powder without the carrier and 12.0 J/g and 1.5 J/g for powder with plant proteins blend). The glass transition temperatures were between 49 °C and 58 °C, depending on the water activity, for powder without carriers and from 45 °C to 54 °C for the one with proteins. • The glass transition temperature between 49 °C and 58 °C for açaí powder without carriers. • The glass transition temperature between 45 °C and 54 °C for açaí powder with plant proteins blend. • Polydextrose as a drying aid reduced glass transition temperature with water activity increased. • Adsorption isotherms of freeze-dried açaí with polydextrose were BET type III. • Adsorption isotherms of freeze-dried açaí with plant protein blend was BET type II. [ABSTRACT FROM AUTHOR]

Unripe acerola powders obtained from freeze-drying without (AV) and with polydextrose (AP) were characterized by using differential scanning calorimetry (DSC) and vapor sorption isotherms at (25, 35, and 45) °C in water activity (a w) range of 0.10–0.90. State diagrams built from DSC results, such as the glass transition (T g) and freezing (T m) points, were compared with those of the sorption isotherms. The Gordon-Taylor equation presented a good fit for T g , in which the solids glass transition increased and the k parameter decreased in the presence of polydextrose. The isotherms obtained were Brunauer-Emmett-Teller (BET) type III, and the Guggenheim-Anderson-de Boer (GAB) equation fitted to the experimental data showed slightly higher monolayer water content for AP, and not affected by temperature. Although there was a divergence in the stability when comparing the criteria of a w and T g , polydextrose increased the a w and T g of freeze-dried unripe acerola and conferred a stabler powder. • The stability criterion between water activity and glass transition was studied. • State diagrams of unripe acerola with polydextrose were built. • Polydextrose used as a drying aid increased the glass transition temperature. • Sorption isotherms of unripe acerola powders were BET Type III. [ABSTRACT FROM AUTHOR]