Rehydration properties of dried plant tissues

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Summary

Apples, carrots and potatoes cut in cubes were dried by convection and then subjected to rehydration in water at room temperature. Mass and volume changes were followed during rehydration. A minimal displacement gauge was used to record changes of height of individual cubes during wetting. Porosity of the dried material was calculated and its changes during rehydration were observed. Comparing volume increase with mass gain during rehydration it was found that the mechanism of water imbibing is strongly influenced by porosity and chemical composition of the dried material. Dried apple was very porous, hence its mass gain was much faster than the volume increase. On the other hand, gelatinised starch in dried potato strongly absorbed water and the volume increase outpaced the mass gain. Recording changes of height of the dried cubes upon rehydration evidenced phase changes and injury incurred to the tissue structure by dehydration. In apple a collapse of structure was observed, while potato cubes swelled from the very beginning of the wetting process. In carrot instantaneous changes of height of the cube were observed, which could be due to relaxation of shrinkage stresses and displacements of injured tissue structures.

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