Kinetic analysis, mathematical modeling and quality evaluation of mint drying in greenhouse solar dryer

Abstract

The goal of this study is to evaluate the potential of the Greenhouse Solar Dryer (GSD) for drying the mint leaves and compare it with other traditional drying methods. The top 10 mathematical models introduced by literatures were selected to describe the drying kinetics of mint leaves. The results showed that the average drying time in the GSD is 32 % and 50 % less than the open sun and shade place drying, respectively. Wang and Singh model with R2 = 0.9944, RMSE = 0.02021 and χ2 = 0.00052, logarithmic model with R2 = 0.9918, RMSE = 0.02556 and χ2 = 0.00078, and Henderson-Dabbie with model with R2 = 0.9774, RMSE = 0.04189 and χ2 = 0.00175 were determined as the best models for GSD, sun and shade place drying, respectively. The amount of changes in the color of the dried mint according to the index of total changes (ΔE) was recorded as 0.53 in the shade place, 0.60 in the GSD, and 0.89 in the open sun drying, respectively. The average of dried mint essential oil that was extracted by hydro-distillation method was 0.0254, 0.0237 and 0.0101 for shade place, GSD and open sun drying, respectively. Comparison of the average amount of extracted dried mint essential oil using ANOVA test, two LSD and Tukey HSD (Honestly Significant Difference) tests showed that there is no significant difference between the two treatments of drying in the shade place and GSD, while both of them have a significant difference with the open sun.