Experimental study of parchment coffee drying using the combined fluidization and microwave process: Analysis of drying curves and thermal imaging

Abstract

In this study, several experimental drying conditions for parchment coffee were investigated using microwave-assisted fluidization. The experiments were carried out in a prototype equipment consisting of a multimode microwave equipment (700 W and 2.45 GHz frequency) with a drying chamber inside of the cavity. Fluidization is provided by a centrifugal blower (1500 rpm nominal) operating at different controlled speeds. The experimental design corresponds to three microwave power levels (0, 210 and 350 W) and different air speeds (0, 1.7 and 3.4 m/s) at 25 and 40 ºC. The experimental moisture evolution and temperature distribution showed that fluidization homogenizes the temperature profiles. Thermographic images further indicated that intermediate microwave power levels (210 W) achieved high uniformity in surface temperature distribution. The combination of fluidization and microwaves facilitated a significant acceleration of the drying rate without exceeding temperature limits, thus preventing any adverse effects on the final product´s quality.