Effects of Main Parameters of a Thin-Layer Dryer on Extraction of the Green Tea Poly Phenols and Drying Duration

In this study, the effects of drying air temperature and airflow rate on the drying duration of semi-dried and completely dried green tea were determined. Also, their effects on the ingredients of the extaction from green tea leaves were determined. Drying temperatures and airflow rates were: 50, 60, 70, 80 and 90 °C and 0.5, 1 and 1.5 m/s. The recorded data were: the drying duration and the amount of poly phenols available in the dried leaves extractions. A factorial statistical experiment was conducted by randomized complete block design. The results showed that with increasing temperature and drying airflow rate, the required time to reach half and completely dried samples are decreased.The variation in the airflow rate at high temperatures did not have any significant effect on drying duration. However, at the low temperatures the variation in airflow rate had significant influence on the drying duration. The amount of poly phenols extracted from green tea leaves dried at high temperatures was more than that for those dried at low temperatures. However, the airflow velocity did not show any significant effect on the indredients of the extraction. Due to destruction of the ingredients of green tea at both high and low temperatures of dryer, it is recommended to use the average temperatures in drying process