Comparative study of fluidized bed paddy drying using hot air and superheated steam

Abstract

This research investigated the physical properties of paddy, i.e., head rice yield, whiteness, white belly, viscosity of rice flour and change of microstructure of rice kernel. The experimental results showed that, for the same duration of drying, drying rates of paddy dried by superheated steam were lower than those dried by hot air due to an initial steam condensation during the first few minutes of superheated steam drying. This initial condition, however, promoted starch gelatinization making head rice yield of paddy dried by superheated steam higher than that dried by hot air. However, the values of whiteness of paddy dried by superheated steam were lower than those dried by hot air, especially during the first few minutes of drying due to a higher degree of Maillard reaction. Nevertheless, no obvious difference between the percentage of white belly of paddy dried by superheated steam and hot air was noted. Measured pasting properties indicated that gelatinization occurred more in paddy dried by superheated steam than that dried by hot air.