Effect of Temperature on Drying Kinetics of Vegetable Seeds

Abstract

A study was conducted to investigate the effect of temperature on drying kinetics of onion, carrot and tomato seed. The seeds were dried at drying temperatures of 30o C, 35o C and 40o C in a laboratory hot-air oven dryer. Drying rate was faster at higher temperature (40o C) than at lower temperatures. Drying of the seeds occurred in falling rate periods of drying. Drying data were fitted into Newton, Page, Modified Page, Henderson-Pabis, Logarithmic, two-term exponential, and Wang and Singh models. Based on highest R2 and lowest χ2 , RMSE and mean error values, Page model (R2 >0.9) was found to be the best fit for drying of all selected seeds at the selected temperatures. However, two-term exponential model was the best fit for onion seed at 35o C and carrot seed at 30o C, and was comparable with Page model in the selected temperature range. Effective moisture diffusivity of onion, carrot and tomato seed ranged between 1.59 x 10-10 m2 .s-1 and 3.18 x 10-10 m2 .s-1, 3.55 x 10-10 m2 .s-1 and 7.10 x 10-11 m2 .s-1, 2.65 x 10-10 m2 .s-1 and 5.31 x 10-11 m2 .s-1, respectively, at above drying temperatures. Activation energies of onion, carrot, and tomato seed were 56.85 kJ.mol-1, 60.69 kJ.mol-1, and 61.44 kJ.mol-1, respectively.