Mathematical modeling of blanch-assisted drying of drumstick leaves (Moringa oleifera) in convective hot air system

Studies were conducted to investigate the drying characteristics and kinetics of pre-drying treated leaves of Moringa oleifera using a hot air oven at 50, 60 and 70 degrees C. The equilibrium moisture content (M-e), moisture ratio (MR) and drying time decreased, whereas the drying rate increased with the increase in temperature from 50 to 70 degrees C. The blanching of the leaves in 0.5 % KMS and 0.1 % NaHCO3 was at par and took less drying time to reach M-e than other pre-drying treatments. Minimum MR was attained in 6.5, 7.0 and 7.5 h in leaves blanched with 0.5 % KMS and 0.5 % NaHSO3 solutions, while in unblanched leaves it was obtained in 7.0, 8.0 and 9.5 h at 50, 60, and 70 degrees C, respectively. The drying rate was higher in 0.5 % KMS pre-drying treatment than the other pre-drying treatments, and the lowest was in unblanched leaves. Among the models, the Midilli-Kucuk model was adjudged as the best fit with highest R-2, lowest reduced chi(2) and the least RMSE. The effective diffusivity of moisture (D-eff) increased while energy consumption (E-c) and specific energy consumption (SEC) of leaves decreased with increasing temperatures from 50 to 70 degrees C. Blanching with 0.5 % KMS solution had the highest D-eff, while, in unblanched leaves, the results were reversed. The leaves blanched with 0.5 % KMS and 0.1 % NaHCO3 solutions required the lowest E-c and SEC while the unblanched leaves had the highest values.