Determination of the drying kinetics and energy efficiency of purple basil (Ocimum basilicum L.) leaves using different drying methods

Abstract

In this work, the effects of different drying methods, namely sun, freeze, convective and microwave oven drying on the drying time, rate and kinetics were investigated in purple basil leaves. Additionally, the energy efficiencies of the driers were determined. All the drying processes took place mainly in the falling-rate period. Comparatively, higher drying rates were obtained from microwave oven drying of the samples. Eleven thin-layer drying models, (Lewis, Page, Modified Page I, Henderson and Pabis, Modified Henderson and Pabis, Logarithmic, Midilli, Modified Midilli, Two-Term, Two-Term Exponential, and Wang and Singh) were fitted to the experimental moisture ratio data. Handerson and Pabis for freeze drying, logarithmic for sun drying and Page for convective and microwave oven drying were found to be the best models for explaining the drying behavior of the purple basil leaves with the highest R2 and lowest RMSE values. The effective moisture diffusivity (Deff) values of the dried purple basil leaves were calculated with Fick’s diffusion model and ranged from 1.62 × 10−9 to 7.09 × 10−8 m2/s. The energy efficiency of microwave oven drying was higher than the other methods.