Kinetics of drumstick leaves (Moringa oleifera) during convective drying.

Abstract

Drying characteristics of drumstick leaves (Moringa oleifera) were investigated in a convective type dryer for a temperature range 50 to 80EsC at constant air velocity, 0.5 m/s. Results indicated that drying took place in the falling rate period. The sample dried at 60EsC was found better in color as compared to the samples obtained at 50, 70 and 80EsC. The chroma of the samples, dried in between 50 to 80EsC was ranged 4.9238 to 9.5258 and was the least, 4.9238 for the sample dried at 60EsC, validating the sensory results. Moisture transfer from drumstick leaves was described by applying the Fick’s diffusion model, and the effective moisture diffusivity was calculated. Effective moisture diffusivity increased with increasing temperature. An Arrhenius relation with an activation energy value of 12.50 kJ/mol expressed the effect of temperature on the moisture diffusivity. Mathematical models were fitted to the experimental data and the performance of these models was evaluated by comparing the coefficient of determination (R2) and reduced chi-square (χ2) between the observed and predicted moisture ratio. Verma model gave the best results for describing the drying kinetics of drumstick leaves.   Key words: Drumstick leaves, convective drying, mathematical modelling, effective moisture diffusivity, activation energy.