Mathematical Modeling of Thin Layer Drying Kinetics and Moisture Diffusivity Study of Pretreated Moringa oleifera Leaves Using Fluidized Bed Dryer

Abstract

Investigations were undertaken to study the drying kinetics of pretreated and unblanched leaves of Moringa oleifera dried in a fluidized bed dryer (FBD) using nine established thin layer drying mathematical models. The statistical software tool Statistica was utilized to carry out regression analysis, and the model constants were evaluated using nonlinear regression. In nonlinear regression, the R2 and reduced χ2 were employed to evaluate the goodness of fit of several mathematical models to the data generated experimentally. The model with the highest R2 and the lowest reduced χ2 and root mean square error (RMSE) values was adjudged as best fit to the drying curves. The drying kinetics of drumstick leaves was best explained by the Midilli–Kucuk model, followed by the Logarithmic model. The R2, reduced χ2, and RMSE values of the Midilli–Kucuk model under fluidized bed drying varied from 0.9982–0.9997, 0.00003–0.00029, and 0.0059–0.0166 in pretreated and 0.9945–0.9961, 0.00019–0.00054 and 0.0136–0.227 in unblanched Moringa leaves dried at 50–70 °C, respectively. The diffusivity (Deff) values ranged between 2.96 × 10−9–3.59 × 10−9 m2 s−1 and 2.92 × 10−9–3.04 × 10−9 m2 s−1, and activation energy varied from 13.67–14.07 (KJ/mol) and 13.85–14.11 (KJ/mol) for pretreated and unblanched dried leaves at 50–70 °C drying temperatures, respectively.