Drying of Apple Purees

Various factors influencing the drying rate of apple purée were investigated. A heated airstream passed over the purée which was contained on a large flat tray. The drying rate could be increased by raising the air temperature, by increasing the air velocity, by promoting turbulence at the tray entrance, by increasing the vertical spacing between trays, and by using metal instead of wooden trays. Three distinct modes of moisture removal were observed during the transition from wet purée to dried apple leather. It was possible to obtain a suitable apple leather product in about 3 hr using 107°C air at 4.6–7.6 m/sec.