Preliminary Investigation of Non-isothermal Drying Kinetics of Wheat as Affected by Initial Moisture Content and Heating Rate Using Model-Fitting Technique

Abstract. In this study, one of the Mid-South available grain, i.e., wheat was dried using a thermogravimetric analyzer. The goal was to study the effects of initial moisture contents and heating rate on the drying kinetics under non-isothermal conditions. Three heating rates (2, 4, and 10^oC/min) were used to determine the drying curves and the weight loss derivatives of wheat from initial moisture contents of 20.7, 16.8 and 13.2% w.b. Wheat was heated from room temperature of 30 to 170^oC to allow a comparison between the drying kinetic parameters. The experimental moisture ratio data were fitted to the four models namely Page, Newton, Logarithmic and Henderson to determine the best-fit model. The goodness of fit criteria was used to determine the best-fit model.

 Heating rate and initial moisture content affected the activation energy required for drying wheat. Increasing the heating rate and drying time expedited the drying curve. The maximum activation energy of 32.876 kJ/mol was achieved at the heating rate of 10°C/min and the initial moisture content of 13.2% w.b. Conversely, the lowest activation energy of 14.760 kJ/mol was achieved at the heating rate of 2°C/min and the initial moisture content of 20.7% w.b. Logarithmic and Henderson were the two models that best fit the entire drying curves. This study revealed that the energy required to dry wheat from 20.7% w.b. to an acceptable safe level could be minimized by reducing the heating rate.