Spouted bed and microwave-assisted spouted bed drying of parboiled wheat

The effect of spouted bed and microwave-assisted spouted bed drying on drying rates of parboiled wheat was investigated. In addition, the effective moisture diffusivities of parboiled wheat were calculated. The drying experiments were performed using 200 g of parboiled wheat, at three different air temperatures (50, 70, 90 °C) and at two different microwave powers (3.5 W/g (db), 7.5 W/g (db)). Microwave-assisted spouted bed drying at microwave power of 3.5 W/g and 7.5 W/g reduced drying time by at least 60% and 85%, respectively compared to spouted bed drying. The effective diffusivity values were in the range of 1.44 × 10−10–3.32 × 10−10 in spouted bed drying while they were between 5.06 × 10−10 and 11.3 × 10−10 in microwave-assisted spouted bed drying at different experimental conditions.

► Microwave-assisted spouted bed drying reduced drying time siginificantly.
► The drying rate increased with air temperature and microwave power.
► Constant rate period was not observed in drying of parboiled wheat.
► The effect of microwave was dominant rather than the effect of air temperature.