Drying characteristics and kinetics of okra

Air-drying characteristics of okra were investigated in a laboratory scale hot-air dryer for a temperature range 50-70 degrees C, and a relative humidity range 8-25%. Results indicated that drying took place in the falling rate period. Moisture transfer from okra was described by applying the Fick's diffusion model, and the effective diffusivity was calculated. Effective diffusivity increased with increasing temperature. An Arrhenius relation with an activation energy value of 51.26 kJ/mol expressed the effect of temperature on the diffusivity. Two mathematical models, the Page and the simple exponential models, available in the literature were fitted to the experimental data. The performance of these models is evaluated by comparing the coefficient of determination (R-2) and reduced chi-square (chi(2)) between the observed and predicted moisture ratio. The Page model gave the best results for describing single layer drying of okra. (c) 2004 Elsevier Ltd. All rights reserved.