Microwave drying of paddy: Drying kinetics and modelling

Abstract

Paddy PR121 variety was dried using microwave at 2450 MHz. The effects of power level (180 - 450 W), air flow rate (3 - 7 m/s) and exposure time (4 - 12 s) for different bed thickness (3 - 6 cm) levels on the moisture content (16- 12%, wb) were analysed by means of response surface methodology. Box-Behnken design was used to develop combinations for the responses. Drying occurred almost under falling rate period. The average value of effective moisture diffusivity (Deff) range between 0.1415 to 0.6580 10−9 m2/s. A prediction of the moisture ratio using Page model provided the best R2, x2 and RMSE in drying kinetics studies. It was concluded that a combination of higher power level and short exposure time or a low power level and a long exposure time might be employed to achieve good drying of paddy.