Exploration of Rough Rice Head Yield Subjected to Drying and Retention Durations in a Fluidized Bed System

Abstract

Abstract.Several researchers have reported that drying freshly harvested rough rice to safe storage moisture content of 14.9% d.b. in fluidized bed dryers resulted in a decrease in head rice yield, as compared with traditional drying methods. This phenomenon was attributed to the high thermal stress that affects rice kernels. The present study hypothesized that drying rough rice in fluidized bed dryers subjected to retention duration would maintain the rice quality as it may reduce the thermal stress. Therefore, the goal of this research was to investigate the effects of heating and retention durations on the dried rice head yield and energy consumption in a fluidized bed dryer. A bench-scale fluidized bed dryer was developed and tested. The effects of drying duration of 10, 20, and 30 min and the retention duration of 0, 15, 30, 45, and 60 min on rough rice moisture content, drying rate, head rice yield, and energy consumption were investigated. During the retention period, paddy released a considerable amount of moisture. This moisture reduction, achieved during retention period, was obtained without any additional heating cost and was a supplement to the overall drying process. The retention period helped with thermal stress management within rice kernels and resulted in maintaining the head rice yield as compared to the rice dried without retention duration. Considering all the studied heating and retention durations, the head rice yield values of rice samples varied from 46.0% to 51.0%. The lowest energy consumption of 3.31MJ/kg waterremoved was achieved at the heating duration of 10 min and the zero retention duration. This value represents 1.44 folds of the theoretical energy required to remove 1 kg of moisture from organic matter. Keywords: Drying, Energy consumption, Head rice yield, Moisture content, Retention duration, Rough rice.