Influence of plant proteins blend or polydextrose on freeze-dried a?al (Euterpe oleracea) sorption isotherms and thermal properties

The influence of polydextrose or plant proteins blend, as a drying aid in freeze-dried acal pulp, was evaluated regarding stability by vapor sorption isotherms at 20 degrees 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, acal powder with polydextrose presented a Brunauer-Emmett-Teller (BET) type III, while the acal powder without and with a plant proteins blend, type II. The freeze-dried acal powders showed two endothermic peaks between-15 degrees C and 10 degrees 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 degrees C and 58 degrees C, depending on the water activity, for powder without carriers and from 45 degrees C to 54 degrees C for the one with proteins.