Modeling of convective drying kinetic of Erythroxylu mminutifolium Griseb leaves

In the present investigation, the drying kinetic of Erythroxylum minutifolium Griseb leaves was studied. The milling leaves were dried in a tray dryer at selected temperatures (50- 70°C), air flow speed (2-4 m/s) and bed depth (10-20 cm). The sorption isotherm of the fresh product was mathematically described by the Guggenheim, Anderson and de Boer (GAB) model, giving as a result monolayer moisture of 0.23 g /g d.b. The results indicated that the drying process takes place in the falling rate period and both the bed depth and the temperature of air are the parameters with most influence in the drying of E. minutifolium leaves. The diffusivity coefficient increased with the temperature from 4.30–5.56 10^-07 m2/s, for a range of temperatures between 50 and 70°C, with an estimated activation energy of 204.13 kJ/mol. Three equations were used for modelling of drying kinetic of leaves. The Page’s model was found the best to fit of the data, showing that this equation correctly simulates the E. minutifolium leaves dehydration process and represents an excellent tool for estimating its drying time.