| Abstract: | The process of drying apple tissue under most conditions may be divided into two main periods viz primary and secondary falling-rate periods. For most drying conditions the secondary falling-rate period is longer and has the greater influence on the overall rate. When the drying capacity of the air is very low an initial constant-rate period may occur. The drying rate constant varies with temperature with an Arrhenius-type relationship and the available evidence suggests that temperature-induced changes in the rate may be caused by vapor pressure changes Air velocity and relative humidity have their greatest influence in the early part of the drying process Towards the end of drying, internal resistance to water movement becomes rate-controlling, and external factors have little influence. An explanation of the observed drying characteristics of apple tissue in terms of the diffusion of water vapour through a ‘skin’ of dried cells is suggested. |
