Microwave heat treatment of leek:: drying kinetic and effective moisture diffusivity

The effect of microwave drying technique on moisture ratio, drying time and effective moisture diffusivity of white and green parts of leek (Allium porrum) were investigated. By increasing the sample amount (100-300 g) at constant microwave output power of 180 W, the drying time increased from 52 to 130 min and increased from 55 to 135 min for white and green parts of leek, respectively. Effective moisture diffusivity values for white and green parts of leek ranged from 0.618 x 10(-10) to 2.128 x 10(-10) m(2).s(-1) and 0.256 x 10(-10) to 0.611 x 10(-10) m(2) s(-1), respectively. Among the models proposed, Midilli et al. model gave a better fit for all drying conditions applied. The activation energy for microwave drying of white and green parts of leek was calculated using an exponential expression based on Arrhenius equation; found as 0.9530 and 1.2045 W g(-1), respectively. The dependence of drying rate constant on effective moisture diffusivity gave a linear relationship.