Effect of continuous steaming on parboiled rice quality

Abstract

A prototype model of a continuous flow steamer was designed and developed taking into consideration the flow characteristics of high-moisture rough rice through a pipe. The model consisted of a hopper to hold soaked rough rice, a steaming section and an outlet to remove gelatinized rough rice at controlled rate. Regulation of rough rice exposure to steam was achieved by manipulating the settings of the discharge mechanism. Rough rice soaked at 60 °C for 5 h and equilibrated overnight was steamed using the device. A 10 ° inclination of the discharge flap and discharge port area of 28.9 cm 2 was found to give optimum quality of parboiled rice with steam supplied at a rate of 9 kg/h and pressure of 1.5 kg/cm 2. Under these conditions, the capacity of the steamer was 104.5 kg/h parboiled rice with 14% moisture content (wb). The developed steamer has a capacity of approximately 2.7 times that of conventional steamers with only about one-third of the steam requirement. These results indicate potential applications for reducing the cost of parboiling equipment by precluding the need for large boilers and steaming tanks with elaborate steam distribution systems, in addition to improvements in the quality of the parboiled rice.