DRYING AND STERILIZATION OF HIGH MOISTURE ROUGH RICE USING CONDUCTION HEATING ROTARY DRYER

A study was carried out to test and evaluate the effect of high-temperature short time conduction heating process using a laboratory scale rotary dryer on sterilization and drying of high moisture rough rice and quality changes of milled rice. The experimental treatments included five different levels of heating surface temperature (10٥, 11٥, 12٥, 13٥ and 1٤٥ºC) and two different grain feed rates (2٫٥ and 3 Kg/patch). Two different drying models (the simple exponential model (Lewis, 1921) and Henderson and Pabis s model (19٦1)) were also examined for describing the drying data. The obtained results showed that: 1- Rapid moisture removal from rough rice was obvious particularly at higher levels of heating surface temperature and lower grain feed rate. 2- For all levels of heating surface temperature, as the exposure time increased, the difference between the grain bulk temperature and the cylinder surface temperature decreased. 3- Both studied models satisfactorily described the drying behavior of high moisture rough rice as indicated from the high coefficient of determination (R²) of the two models. However, Lewis s model could be considered most proper for describing the drying behavior of rough rice. ٤- Heating surface temperature of 11٥ºC with grain feed rate of 3 Kg /patch recorded the highest quality of milled rice.