Electrohydrodynamic, oven and natural drying of mint leaves and effects on physiochemical indices of the leaves

Electrohydrodynamic (EHD) enhanced the thin-layer drying of mint (Mentha Spicata Huds) leaves using multiple point-to-plate electrodes. Its configurations were carried out under a DC high voltage and its effects compared to oven drying at 40˚C and open-air-drying with natural convection at 25˚C. The EHD was run in an optimum electric field of 3.2 kV/cm using positive ionizing conical needles to a plate electrode covered by a steel screen grid to prevent leaves drift. The samples subjected to the EHD and oven exhibited faster drying kinetics than natural convection. Compared to the oven drying, the EHD electrical power consumption was negligible. The EHD fewer developed undesirable changes in color features and leaves total chlorophyll, whereas the oven-dried sample color underwent a significant difference in color. The samples dried by EHD had lower active microorganisms. Empirical modeling based on the maximum value of R2 and minimum value of RMSE and SSE between the experimental and predicted moisture ratios showed that diffusion and logarithmic were the best models for describing the EHD and oven drying behavior of mint leaves.

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