Comparison of rehydration
Rehydration capacity is not only influenced by the product composition, water temperature and rehydration time, but also highly related to drying methods and processing parameters (Zhang, 1996). During the drying process, the water is gradually reduced, inducing irreversible cell damage and dislocation, and leading to structure collapse and integrity loss of cells, therefore resulting in the loss of the hydrophilic property. The product rehydration depends primarily on the degree of structure damage of cells (Krokida and Maroulis, 1999). In general, freeze dried product has good performance of rehydration due to its low temperature drying conditions and less damaged cell structures, however long-time cooling, drying and vacuuming make it high cost. The effect of different drying technologies on the rehydration c a p a b i l i t y i s s h o w n i n F i g u r e 1 .