Structural properties for fruits and vegetables during drying

In order to examine the structural properties of fruits and vegetables in drying process, apparent density, true density, internal porosity and specific volume on a dry basis for five kinds of vegetables, which were radish, carrot, eggplant, potato and sweet potato, were determined at various moisture content. Volume shrinkage of sample with hot air drying was related to a linear function of moisture content. The relationship of apparent density and internal porosity for five kinds of vegetables to moisture content gave two different tendencies. One was a linear function of moisture content for radish and carrot, and the other was a quadratic function of moisture content for eggplant, potato and sweet potato. True density increased exponentially as the moisture content decreased. Therefore, effects of the hardening of sample caused by loss of water and heating on structural properties of them in the drying process were estimated.