Comparison of drying parameters and qualitative characteristics of paddy (Tarom Hashemi) using a continues and a domestic microwave dryer

Paddy drying is one of the most important and critical post-harvest processes of rice in order to prevent the growth of germs and fungi; which enhances the product storage time. In this study, drying process of Tarom Hashemi was evaluated in a continuous band microwave dryer and in a domestic microwave dryer. The obtained results indicated that the moisture ratio decreased by increasing the paddy thickness from 6 to 18 mm and the microwave power levels from 10 to 30%, whereas the seed breakage increased. The drying ratio in the domestic microwave dryer was always less than that in the continuous band microwave dryer except at the 10% input power level, whereas the seed breakage percent was always more in the domestic microwave dryer in comparison with the continuous band microwave dryer. The results indicated that the moisture diffusion coefficient was larger in drying with continuous band microwave dryer in comparison with the domestic microwave dryer at 10% microwave power levels, whereas this coefficient was less at the 50% microwave power. As a final conclusion, the use of household microwave dryer for drying the paddy is not recommended due to high percentage of seed breakage. In contrast using a continuous band microwave dryer with low input power levels (e.g., 10%) is recommended on a large scale due to the rapid moisture reduction and low seed breakage percentage.