Critical water activity and critical water content of freeze-dried strawberry powder as affected by maltodextrin and arabic gum

The adsorption isotherms (20 degrees C) and the relationship between water content and glass transition temperature were modeled in freeze-dried strawberry powder studying the effect of the addition of maltodextrin and arabic gum. Both compositional and physicochemical analyses of strawberry pulp were performed. If the midpoint of the glass transition is considered, the critical water activity that ensures the glassy state of the product during storage at 20 degrees C increased from 0.094 to 0.237-0.341 when maltodextrin and arabic gum were added, respectively. The increase in the critical water content was not so marked and it was noticeable only in arabic gum added sample (from 7.5 to 8.9 g water/100 g product), being this sample more stable. (c) 2011 Elsevier Ltd. All rights reserved.