食品乾燥における有効表面積に関する一考察

The effective drying surface area of cellulous foodstuffs was investigated in this study. Onion epidermis was used as a sample. It was dried in an air dryer, and the changes in shape of the epidermis cells in the drying process were microscopically observed and photographed. The results showed that the volume of the cell decreased or collapsed and its surface rumpled gradually as the drying process proceeded. But the projection area of the cells did not vary so much. Thus it was considered that the change in net surface area of the epidermis might be little, though the volume change of the cells was of an appreciable amount. This assumption was verified by calculating the net surface area from the replica images of onion epidermis. The net surface area was proved to be about 1.8 times as large as the apparent surface area. However, the drying rates per unit apparent area of agar gel plate with a smooth surface were nearly equal to those of onion epidermis. Therefore, we concluded that the effective drying surface area of cellulous foodstuffs might be approximated to the apparent surface area.