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Effect of Drying on the Physical Characteristics of Black Leaf Tea
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 036110, 2003 ASAE Annual Meeting . (doi: 10.13031/2013.14201) @2003Authors: Hongbo Song, Zhihuai Mao, Guoping Lian
Keywords: Black leaf tea, Physical characteristics, Fluidized bed drying, Vacuum dying, Microwave drying
The effect of drying process on the physical characteristics of black leaf tea has been investigated. Fermented dhool of black leaf tea was dried using different methods including fluidized bed, vacuum and microwave drying. Experiments have been carried out to measure the drying kinetics, relative humidity and exit air temperature during fluidized bed drying. The physical properties of the dried product were assessed by moisture content, particle size distribution and average particle size. With fluidized bed drying, there are two drying periods for CTC dhool: the constant drying rate drying period and the falling drying rate period. The drying rate was relatively fast and depended on the drying temperature. However, with microwave drying, only one drying period for Freedom leaf tea was observed and the drying rate was slower. There is positive linear relation for CTC dhool but not for Freedom dhool between drying temperature and average particle size during fluidized bed drying. With vacuum drying and microwave drying, there is positive linear relation for Freedom dhool between drying temperature, microwave intensity and average particle size.
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