Drying kinetics of organic parchment coffee beans (Coffea arabica L.) using microwave fluidised bed: Semi-theoretical modeling

The aim of this study was to model the drying kinetics of microwave and fluidised bed of parchment coffee bean (Coffea arabica L.) using a semi-theoretical approach. A completely randomized design with six treatments: three with microwave drying (MD) and the rest combined with fluidized bed drying (MFBD) was carried out. The drying curves were established until reaching a final moisture content between 10 to 12% w.b. The results indicated that the drying time decreased as the microwave power level increased. When MFBD was used, drying times increased approximately 4-fold compared to MD treatments. The values of effective diffusivity for coffee beans treated with MD and MFBD ranged from 0.913 to1.72×10-9 m2.s-1 and 0.23 to 0.42×10-9 m2.s-1, respectively. Although all the models presented high goodness of fit, the two-term model presented the highest R2 (0.9855 – 0.9978) and lowest RMSE (0.0128-0.0285). In general, all models adequately fitted the experimental data so they can be used to predict the drying kinetics, therefore they could be very useful in equipment design and optimization of the coffee drying process.