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KMID : 1007520070160050771
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Food Science and Biotechnology
2007 Volume.16 No. 5 p.771 ~ p.777
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Dehydration Kinetics of Rehmannia (Rehmannia glutinosa Liboschitz
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Rhim Jong-Whan
Kim Ji-Hye
Jeong Won-Chul
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Abstract
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Sliced and whole root of rehmannia were dehydrated in a laboratory dryer at 40, 60, 80, and 100℃ to evaluate the kinetic parameters for dehydration of rehmannia. The drying curves of both samples were characterized by a falling-rate drying period only. Sliced rehmannia dried 1.1 to 3.1 times faster than whole root of rehmannia depending on drying temperature. Equilibrium moisture content (EMC) of rehmannia samples at the drying temperature tested were 0.069-0.078 g water/g dry solid, which was coincided with the monolayer moisture content (0.06 and 0.07 g water/g dry solid) evaluated from desorption isotherms using GAB (Guggenheim-Anderson-de Boer) model. A logarithmic model for thin layer drying was applied to evaluate the drying time to reach EMC (tEMC) and drying constant (k). The effect of temperature on 1/tEMC and k was described by the Arrhenius model with activation energy values of 32.56 and 47.14 kJ/mol determined using the former parameter, and 34.27 an 38.26 kJ/mol determined using the latter parameter for sliced and whole root of rehmannia, respectively.
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KEYWORD
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rehmannia, jiwhang, dehydration, kinetics, Logarithmic model
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