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KMID : 0380919960250020318
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Journal of the Korean Society of Food Nutrition
1996 Volume.25 No. 2 p.318 ~ p.324
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The Drying Characteristics of Korean Tea - Leaves by Processing Methods
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Seo Jae-Sin
Hur Jong-Wha
Choi Byoung-Min
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Abstract
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The drying constants and diffusion coefficient of Korean tea-leaves during hot air drying were determined with respect to different drying temperatures, plucking times, heating methods, and rolling conditions. Higher drying temperature, later plucking time, and repeated rolling contributed to increasing the drying constant of tea-leaves, which means faster drying. The drying constant was determined to be high in the samples heated several times before drying. The average drying constants were calculated as 0.356, 0.425, and 0.77/hr for the sample of the 1st, 2nd, and 3rd tea-leaves ; 0.403, 0.418, and 0.438/hr for natural, steamed, and roasted tea-leaves, respectively. The diffusion coefficient of moisture in tea-leaves was affected by width and diameter of the samples, temperatures and rolling frequency. The average values of moisture diffusion coefficient were 1.162×10^(-8), 1.986×10^(-8)㎡/hr for natural, steamed, and roasted tea-leaves ; 7.00×10^(-7) and 1.130×10^(-7)㎡/hr for leaves and stems, respectively. Activation energies of diffusion were calculated as 9.50, 9.48, and 9.51㎉/㏖ for steamed and roasted tea-leaves ; 10.33 and 8.67 ㎉/㏖ for leaves and stems, respectively.
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KEYWORD
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Korean tea-leaves, drying constants, diffusion coefficient, activation energies
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