MOISTURE DIFFUSION IN ALLSPICE (PIMENTA DIOICA L. MERRIL) FRUITS DURING FLUIDIZED BED DRYING

Abstract

ABSTRACT Allspice fruits (Pimenta dioica L. Merril) were dried in a laboratory fluidized bed dryer at three different inlet air temperatures (60, 70 and 80C), three different initial bed mass loads (0.300, 0.450 and 0.600 kg) and an air velocity of 3.4 m/s. The mean effective diffusion coefficients were obtained by analyzing the drying curves with Fick's second law diffusional model for a spherical geometry, and ranged from 1.37 × 10−10 to 4.66 × 10−10 m2/s for moisture contents between 0.072 and 2.000 kg water/kg dry solids. An Arrhenius-type relationship was used for estimating the activation energy (Ea) required for moisture diffusion at a given temperature. The values for Ea were nonsignificantly different (55.78–59.89 kJ/mol) for the different initial bed mass loads. Fick's model describes successfully the allspice drying process. PRACTICAL APPLICATIONS An important contribution of the present work was to quantify the mean effective diffusion coefficient of water and the estimation of the activation energy required for water diffusion in allspice fruits undergoing fluidized bed drying process. By doing this, a better understanding of the drying process was achieved, which in turn may result in the production of higher-quality allspice dehydrated products.