INFRA-RED DRYING AND STERILIZATION OF HIGH MOISTURE ROUGH RICE

A study was carried out to test and evaluate the effect of high-temperature short time Infra-red heating process using a laboratory scale rotary dryer on drying and sterilization of high moisture rough rice and quality changes of the milled rice. The experimental treatments included five different levels of radiation intensity (0.973, 1.033, 1.093, 1.129 and 1.161kW/m²) and two different grain feed rates (2.5 and 3 Kg/patch). Two different drying models [the simple exponential model (Lewis, 1921) and Henderson and Pabis s model (1961)] 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 radiation intensity and lower grain feed rate. 2- Bulk temperature of the heat treated rice samples ranged from 39.1 to 133.3 ºC depending upon the radiation intensity, exposure time and grain feed rate. 3- Both studied models could satisfactorily describe the drying behavior of high moisture rough rice. However, the Lewis s model considered most proper for describing the drying behavior of rough rice due to simplicity of this model in calculations and analysis. 4- The high levels of infra-red radiation intensity reduced the fungal load in high moisture rough rice in an effective manner. 5- A reduction in broken percentage was observed as the radiation intensity decreased and grain feed rate increased. 6- Infra-red heat-treated rough rice yielded milled rice slightly yellowish in appearance in comparison with the sun dried sample.