MICROWAVE-DRYING CHARACTERISTICS OF BASIL

Abstract

The effect of microwave-drying technique on moisture content, moisture ratio, drying rate, drying time and effective moisture diffusivity of basil leaves (Ocimum Basillium L.) were investigated. By increasing the microwave output powers (180–900 W) and the sample amounts (25–100 g), the drying time decreased from 28 to 6.5 min and increased from 16 to 44 min, respectively. To determine the kinetic parameters, the drying data were fitted to various models based on the ratios of the differences between the initial and final moisture contents and equilibrium moisture content versus drying time. Among the models proposed, the semi-empirical logarithmic model gave a better fit for all drying conditions applied. The activation energy was calculated using an exponential expression based on Arrhenius equation. The relationship between the drying rate constant and effective moisture diffusivity was also estimated and gave a linear relationship. PRACTICAL APPLICATIONS Drying, in general, means removal of water from the material. The purpose of drying food products is to allow longer periods of storage with minimized packaging requirements, reduce shipping weights and preserve seasonal plants and make them available to consumers during the whole year. Besides these advantages, some important changes take place, as structural and physicochemical modifications that affect the final product quality during dehydration. Microwave drying is an alternative method because of its uniform energy and high thermal conductivity to the inner sides of the material, space utilization, sanitation, energy savings, precise process control and fast startup and shutdown conditions. In the present study, drying kinetics of basil were investigated in a microwave oven at various microwave output powers and sample amounts. Drying time decreased considerably with increased microwave output power and with decreased sample amount of basil as well by using microwave-drying technique.