ABSTRACT Gambir is one of the leading agricultural commodities of North Sumatra Province, Indonesia. One of the post-harvest processing steps for gambir leaves is drying. In this work, a flat-bed dryer (FBD) powered by a biomass pyrolysis reactor has been studied for the drying of gambir leaves. The vertical distance of the flat-bed position from the hot air channel was varied (20 cm, 40 cm, 60 cm) to explore their effect on the drying behavior, kinetic, and quality of gambir leaves. The results showed that the optimal flat-bed position was found to be 40 cm, resulting in a drying time of 95 minutes, a final moisture content of less than 1%, and the highest drying rate among the positions. The effective moisture diffusivity (D eff ) ranges from 3.489 × 10 -9 to 8.205 × 10 -9 m 2 /s. The Hasibuan–Daud model was identified as the most suitable for describing the experimental drying data at flat-bed position of 40 cm, while Page model being the best model for flat-bed position of 20 cm and 40 cm. The drying process reduces fatty acid levels as analyzed by GC-MS, and causes shrinkage of the surface of gambier leaves as observed by SEM. Interestingly, drying did not significantly affect the catechin content of gambir leaves, due to the low RH and moderate temperature in the drying chamber. Overall, this drying system is suitable for quickly drying gambir leaves while maintaining their quality.
Hasibuan et al. (Fri,) studied this question.