Abstract

In this study the effectiveness of drying methods - vacuum microwave drying (VMD), hot air drying (AD), convective air drying combined with vacuum microwave drying (AD-VMD) and osmotic dehydration followed by vacuum microwave drying (OD-VMD) - and their effects on both physicochemical and structural changes in strawberries are compared. Drying performance was assessed by drying rate, moisture content and water activity, while changes in quality attributes of strawberries were determined by measuring color, texture, microstructure, shrinkage and rehydration ratio. A maximum drying rate of 6.74 x 10(-4) kg water/(kg dry matter s) was found for microwave-assisted drying, which results into a product of intermediate water activity. Combining VMD with osmotic dehydration or air drying did not improve drying efficiency. VMD yields an elastic product of improved mechanical resistance with just a slight loss of color and an appropriate rehydration performance. Preliminary dehydration using hot air or sucrose solution was not able to improve most of the quality attributes of strawberries. (C) 2014 Elsevier Ltd. All rights reserved.