Carrot volatiles monitoring and control in microwave drying

Volatiles emanating from carrot [Daucus carota L cv. 'Enterprise'] samples dried in a microwave oven were monitored throughout the drying process with a zNose (TM). Drying temperatures were first set to 50 degrees C, 60 degrees C, 70 degrees C, and 80 degrees C. Six typical volatile peaks were recorded every 4 min for each of the three replicate runs. Color and sensory evaluation were performed after drying. Samples could be dried in a short time at high temperatures but the interior of some samples was charred. Longer time and more energy were required at low temperature drying. A fuzzy logic control system was then designed and employed to control the drying temperature throughout the whole drying process, using detected volatile peaks as variables. Based on the fuzzy logic controlled temperature curve, a simple linear control method was developed. It was shown that carrot quality was intact and time and energy were saved with these new control strategies. (C) 2009 Elsevier Ltd. All rights reserved.