State diagrams of freeze-dried camu-camu (Myrciaria dubia (HBK) Mc Vaugh) pulp with and without maltodextrin addition

The state diagram for freeze-dried natural camu-camu pulp and for pulp with 30% maltodextrin DE 20 were determined by differential scanning calorimetry (DSC). Freeze-dried samples were equilibrated at 25 degrees C over saturated salt solutions in order to achieve water activities between 0.11 and 0.90. Higher water activities were obtained by direct water addition on the freeze-dried product. Gordon-Taylor model was able to predict the plasticizing effect of water in the low and intermediate moisture content range. In the high moisture domain (a(w) > 0.90), T-g was practically constant, representing the glass transition temperature of the maximally concentrated phase (T'(g)), which were -58.8 degrees C and -40.1 degrees C for natural pulp and pulp with maltodextrin, respectively. (c) 2005 Elsevier Ltd. All rights reserved.