Drying of thyme (Thymus Vulgaris L.) and selection of a suitable thin-layer drying model

Abstract

The air drying characteristics of thyme was investigated at a temperature range of 40-60C and at an air velocity of 2.0m/s. The drying time varied from 120 to 495min. Increase in air temperature significantly reduced the drying time of the thyme. Effective moisture diffusivity was estimated using the analytical solution of Fick's law of diffusion. It was found to be in the range of 1.097-5.991×10 -9m 2/s in the temperature range. The temperature dependence of the effective moisture diffusivity was described by the Arrhenius relationship with activation energy of 73.84kJ/mol. Twelve mathematical models were evaluated by using the coefficient of determination (R 2), mean relative percent error (P), reduced chi-square (χ 2) and root mean square error. The drying characteristics of thyme were well predicted by the Midilli etal. model within the limits of the experiment. Rehydration behaviors were affected by the drying temperature and were found to increase with drying temperature. © 2010 Wiley Periodicals, Inc.