Evaluation of energy efficiency and moisture diffusivity for convective drying of large cardamom

Abstract

Abstract The drying behavior of freshly harvested large cardamom capsules were studied in a hot air dryer within the temperature range of 50-80°C. The study on drying rate showed that the constant rate drying period was very short, and capsules mostly followed the falling rate drying period. The drying during falling rate drying was followed unsteady state mass transfer and was governed by Fick’s diffusion law. The drying rate was faster initially when the moisture content in the product was high but with a decrease of moisture content, the drying rate was found to be decreased. Nine different drying kinetics models were fitted to find the best suitable model to predict the drying kinetics of large cardamom capsules. The two-term model was the best-suited model out of the nine different models, representing the drying properties of large cardamom with the highest R2 and the lowest RMSE and χ2 values. The maximum effective moisture diffusivity Deff value of 3.898×10−10 was obtained at a drying temperature of 80°C, while the lowest value was 1.949×10−10 at 50°C. The dependency of effective moisture diffusivity with drying temperature was correlated by Arrhenius equation. The activation energy showing the minimum energy needed to extract moisture from a solid matrix of large cardamom capsule was calculated as 32.54 kJ/mol and the pre-exponential factor of Arrhenius equation was calculated at 7.6×10−4 m2/s.