Study on the Mass Transfer and Drying Kinetics of Allium stipitatum by Microwave Method

Shallot (Allium stipitatum) is one of the native plants of Iran with antioxidant and antimicrobial properties. In this study, the effect of microwave method (in the powers of 450, 600, 750 and 900W) on drying characteristics of Shallot was investigated. Process kinetics study showed that among 10 common mathematical models, two term model was the best choice in the power range of 450 to 900W. As the power of the microwave increased, the drying time was decreased and its drying rate was increased. The minimum drying time was 18 minutes at 900 W, which was 95.5% less than hot air drying time (400 minutes). The results showed that with increasing microwave power, the diffusion coefficient increases and the activation energy decreases. The maximum effective moisture diffusivity was obtained 1.2×10-7 (m2/s) and the minimum activation energy was obtained 5.3 W/g for microwave power of 900 W. The optimum power was 450W in terms of total color change (∆E) and 900W in terms of browning index (BI).