Cocoa Beans Microwave Pulse Drying: Characterization of the Moisture Transfer

Abstract

The aim of this study was to characterize the moisture transfer during microwave pulse drying of cocoa beans. Experiments were carried out on fermented cocoa beans using a domestic microwave oven. Three microwave power levels (450 W, 600 W and 700 W) were used. The moisture transfer characterization was made using the estimation of mass transfer parameters and a modeling. The estimated mass transfer parameters were the Biot number (Bi), the diffusivity (D) and the mass transfer coefficient (km). They were given by the analytical method of Dincer. The 2nd Fick’s law was used for the moisture transfer modelling. The results obtained showed that for the whole microwave powers, the Bi values were included between 0.57 and 0.62. The D values, for the various microwaves powers (450 W, 600 W and 700 W), were respectively 6.01×10-9 m².s-1, 10.27 ×10-9 m².s-1and 11.94×10-9 m².s-1. The km values varied between 9.87×10-7 m.s-1and 21.33×10-7 m.s-1. The Fick’s model application showed a good adequacy between the experimental values and those simulated. R² of the Fick’s model for the whole microwave power levels, was higher than 0.998.