Thin-layer infrared radiation drying of onion slices

A laboratory scale infrared-convective dryer was developed and single layer drying of onion slices was carried out at infrared power levels of 300, 400 and 500 W, drying air temperatures of 35, 40 and 45 degreesC and inlet drying air velocities of 1.0, 1.25 and 1.5 m/s. The drying time reduced by about 2.25 times on increasing infrared power from 300 to 500 W, air temperature 35-45 degreesC and air velocity from 1.0 to 1.5 m/s. Effective moisture diffusivity varied from 0.21 x 10(-10) to 1.57 x 10(-10) m(2)/s and was significantly influenced by infrared power and air temperature.. The rehydration ratio of dehydrated onion slices was found to be in the range of 4.5 and 5.3. (C) 2004 Elsevier Ltd. All rights reserved.