Main Article Content
This research aimed to design and develop the continuous paddy steaming machine for the production of hang rice or parboiled rice for community enterprises and small enterprises. The paddy-steaming machine was cylindrical shape and made of stainless steel with a height of 4800 mm and diameter of 250 mm. The loading capacity of paddy in the machine was 96.66 kg. There was steam pipeline at the middle machine. Flow rate of steamed paddy was controlled by speed of screw conveyor. The RD31 paddy was soaked in water at room temperature for 12 hours and moisture content of the paddy was 31.14 ±0.78 % (w.b.). Steam condition in this experiment was 0.4 Barg and 109.5◦C. The steaming time of paddy was controlled by the speed of the screw conveyor by using a variable frequency inverter. The screw speed was 10.2, 15.4, and 20.6 rpm at the three frequencies (5, 7.5 and 10 Hz). The sample of paddy was collected at first 15 minutes and every 10 minutes until 105 minutes. The steamed paddy was left to cool down and dry in the air conditioned room with temperature of 27-28 °C and 63% RH for 4 days. The final moisture of paddy was 11.65 -13.13% (w.b.). The paddy was milled and the head rice yield of brown rice, head rice yield of milled rice, broken rice, chalky kernels and color of the milled rice were determined. The results showed that flow rate of rice was 0.70 ± 0.01, 1.06±0.01 and 1.42±0.07 kg/min at the screw speed 10.2, 15.4, and 20.6 rpm respectively. By increasing the steaming time, the percentage of head rice yield and the yellow color value of parboiled rice increased but chalky kernels decreased. The suitable time for streaming the RD31 paddy was 35 minute at speed of screw conveyor 20.63 rpm. At this condition, the head rice yield of brown rice was 71.76%; the head rice yield of milled rice was 65.83%. The percentage of chalky kernels reduced from 23% (before steaming) to 4% (after steaming). The yellow value (b*) of rice increased to 16.31±1.12%.