Evaluation of low temperature drying characteristics of fresh tea leaves (Camellia assamica) in an environmental chamber using mathematical models

Abstract

Low-temperature drying (withering) is the first stage in black tea processing. Determination of appropriate end moisture content of green tea leaf as well as temperature and relative humidity (RH) maintained during withering eventually aid the final quality of the processed tea. Therefore, the tea leaf withering (partial drying) properties were evaluated in an environmental chamber using mathematical models. The temperatures and RH considered were 25, 30, 35 °C and 80, 85, 90%, respectively. A total of nine combinations of temperature and RH were considered by keeping one parameter constant. The conditions were taken adhering to that of the climatic conditions of Assam, India. The withering data from experiments were fitted into five drying models using the curve fitting method. The Page model gave better predictions with an R2 value of 0.9989 at 30 °C temperature and 90% RH. The total phenolic and flavonoid contents of the tea leaf samples were evaluated. The best results were 50.60 ± 0.02 mg GAE.g-1 (GAE - gallic acid equivalent) and 22.47 ± 0.01 mg QCE.g-1 (QCE - quercetin equivalent) at 30 °C withering temperature.

Keywords

• fit
• green tea-leaf
• humidity
• moisture ratio
• wither