Effect of Soaking Temperature and Steaming Time on the Quality of Parboiled Iranian Paddy Rice

Iranian paddy (Fajr) is the most popular rice for export and consumption in Iran but it has poor milling yield. To solve this problem, parboiling has been used for improving its milling quality. In this study, the effect of various parboiling conditions (soaking at temperatures of 55-75 degrees C and steaming times for 2-10 min) on some quality properties of Fajr paddy was investigated. After parboiling, the physical properties (degree of milling, head rice yield, lightness and color value) and mechanical properties (rupture force) of parboiled rice were measured. Head rice yield and mean value of rupture force increased significantly (p < 0.05) from 50.10% to 62.11-67.05% and from 108.6 to 128.93-227.30 N, respectively. Also, the color value of parboiled rice increased significantly (p < 0.05) by increasing the length of steaming time. The milling degree of unparboiled rice (17.03%) was significantly (p < 0.05) higher than that of the parboiled rice (15.1-16.9% range). Soaking at 65 degrees C and 4 min steaming time gave the highest values of head rice yield, lightness and rupture force. So, this treatment was found to provide the most desirable quality of Fajr parboiled rice.