Optimization of Drying Parameters for Minimization of Moisture Content in Black Tea Production

Abstract

Study focuses on black tea drying process on fluidized bed dryer in tea factories. Tea drying variables considered in the study were air temperature, air velocity and time. The response variable in the experiment was the black tea moisture content. Air velocity was varied between 0.21 m/s and 0.55 m/s. Whereas air temperature was varied between 70 ⁰C and 130 ⁰C.  Drying time ranged between 0 minute and 20 minutes. Black tea drying experiment was conducted in the macerated tea laboratory at Sotik Tea Company using the miniature FBD Sherwood Tornado model 501. It took 20 minutes experimental time to lower the dhool moisture from 72% to 3.5%. Experimental data was used to develop black tea drying curve and drying rate.  The Box Behnken design under response surface design methodology in Minitab software was used to analyze and optimize the black tea drying variables. The optimum variables were found to be at hot air temperature of 100 ⁰C, hot air velocity of 0.38 m/s and drying time of 12.9 minutes. These drying parameters resulted in a more acceptable black tea moisture content of 3.5% db which falls between the acceptable black tea moisture content of 3% db to 4% db.