Production of an herbal green tea from ambang ( Xymalos monospora) leaves: Influence of drying method and temperature on the drying kinetics and tea quality

Decoctions of ambang (Xymalos monospora) leaves are claimed to have therapeutic potentials but they are seasonal and highly perishable because of its high moisture content. To improve on the use of this plant, drying studies were carried out on its leaves in an effort to produce a green tea. Green tea was produced under 3 different drying conditions including shade, sun and electric drying. The effects of drying method and temperature (50, 60 and 70 °C) on the kinetics, proximate composition and total phenolic content of the teas were analyzed. Drying method had a significant effect on the drying kinetics and quality of the green tea produced. Drying occurred entirely in the falling rate period suggesting that the principal mechanism of drying was by diffusion. Kinetics of the drying processed were modeled successfully by the Page and Modified Page equations. Activation energy for the drying process as determined using K-values from the modified page equation was 27.89 kJ/mol. Significant differences were observed in the quality parameters of teas produced. Protein, carbohydrate and total phenolic content were also dependent on the type of solvent used for extraction. The green tea produced at 60 °C had most of its properties comparable to the commercial green tea used as a reference in the study. It is recommended that to produce good quality tea from ambang leaves, drying should be done at 60 °C for 6 h to obtain a tea with the following composition; moisture content (6.56 ± 0.01), total polyphenols (8.29 ± 0.08), Proteins (2.99 ± 0.13), ash (8.40 ± 0.15) and fiber content (20.43 ± 2.60).

Keywords: Activation energy; Drying; Green tea; Polyphenol; Xymalos monospora.