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Speed Control in Microwave Drying Of Apple

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1009275.(doi:10.13031/2013.29841)
Authors:   Zhenfeng Li, G.S.V Raghavam, Ning Wang, Clement Vigneault
Keywords:   Microwave drying, drying curve, control, apple

Microwave drying of apple at constant temperatures of 50 80 C follows typical drying curves. The middle stage of the drying process shows a faster drying speed and accelerated moisture evaporation. Meanwhile, more flavors are lost, surface color is degraded, and charring often occurs. To improve the drying effects, drying curves were controlled and changed in this study. The drying curve was linearized by automatically varying drying temperatures in the middle stages. A microwave drying system with the ability of temperature, power, and moisture control was developed for this purpose. The controlled drying process therefore led to an optimized temperature profile. To simplify the drying methods, apples were further dried with the obtained temperature profile, while drying curves were online monitored but not controlled. It was proved that slowing down the drying speed in the middle stage could improve the product quality on color, flavor, and overall appearance, while the drying time and energy consumption were still acceptable.

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