Dehydration of SteviarebaudianaBertoni Leaves: Kinetics, Modeling and Energy Features

The drying process of Stevia leaves was studied from 30 to 80C. Experimental drying curves showed that the drying process took place only in the falling rate period. Effective moisture diffusivity of Stevia leaves was in the range of 4.67-14.9x10(-10)m(2)/s. Several drying models available were evaluated based on statistical tests as a sum squared error (SSE), chi-square and determination coefficient. A value of 38.78kJ/mol was determined as an activation energy. When comparing the experimental with predicted drying curves, the Midilli-Kucuk model was found to give the best fit quality (SSE<0.001, (2)<0.001, r(2)>0.99). In addition, all drying curves were generalized and then modeled by Midilli-Kucuk model (r(2)=0.99), showing this equation can very accurately predict the drying time of Stevia leaves under the drying conditions studied. At last, energy consumption and efficiency values for Stevia leaves drying process were found to be in the range of 316.59-716.19kJ/kg and 21.46-54.34%, respectively. Practical ApplicationsA great demand for medicinal plants with extended shelf life has urged the dried food industry to look for raw materials of desirable nutritional and functional properties. Stevia rebaudiana leaves, with its high content of biologically active health-promoting components (natural non-caloric sweetener compounds, antibacterial capacity, antioxidant activity and other), is therefore an excellent raw material for the healthy food industry. Dehydration has the potential to deliver safe food products through decreasing moisture content and water activity. Therefore, knowledge about moisture transfer kinetics, as well as energy consumption and/or data normalization, is needed by the industry to manage and control efficiently drying process. Thus, this could serve to demonstrate the environmental consciousness of the food processing industry, greatly appreciated by consumers.