Influence of process conditions on the physicochemical properties of acai (Euterpe oleraceae Mart.) powder produced by spray drying

The objective of this work was to study the influence of spray drying conditions on the physicochemical properties of acai powder. The process was carried out on a mini spray dryer and maltodextrin 10DE was used as carrier agent. Seventeen tests were made, according to a central composite design. Independent variables were: inlet air temperature (138-202 degrees C), feed flow rate (5-25 g/min) and maltodextrin concentration (10-30%). Moisture content, hygroscopicity, process yield and anthocyanin retention were analysed as responses. Powder moisture content and process yield were positively affected by inlet air temperature and negatively affected by feed flow rate, which are directly related to heat and mass transfer. Process yield was also negatively influenced by maltodextrin concentration, due to the increase on mixture viscosity. Powders hygroscopicity decreased with increasing maltodextrin concentration, decreasing temperature and increasing feed flow rate. Powders with lower moisture content were more hygroscopic, which is related to the greater water concentration gradient between the product and the surrounding air. Anthocyanin retention was only affected by temperature, due to its high sensitivity. In respect to morphology, the particles produced at higher temperature were larger and a great number of them showed smooth surface. (C) 2008 Elsevier Ltd. All rights reserved.