Development of combined infrared and hot air dryer for vegetables

Application of combined electromagnetic radiation and hot air is gaining momentum in food processing. A combined infrared and hot air heating system was developed for drying of vegetables. A conveyorised drying system having three chambers was fitted with mid-infrared (MIR) heaters for radiative heating. Through-flow hot air circulation was also provided for convective mode heating. The system was designed to operate under infrared, hot air and combination mode independently. The performance evaluation studies indicated that combination drying of carrot and potato at 80 degreesC with air at a velocity of 1 m/s and temperature of 40 degreesC reduced the drying time by 48%, besides consuming less energy (63%) compared to hot air heating. Combination drying also gave better results over infrared heating alone. The energy utilization efficiency of the dryer was estimated to be 38% for both carrot and potato drying. (C) 2004 Elsevier Ltd. All rights reserved.