Parboiling to improve milling quality of Selam rice variety, grown in Ethiopia

Abstract

Conventional rice milling produces a high percentage (40%) of rice breakage. The parboiling process is, therefore, considered the best solution for reducing the susceptibility of the rice grain to breakage in addition to varietal characteristics and quality of milling machine. The parboiling process hardens the rice kernel enabling it to withstand the machine’s impact and reduce breakage during the milling process. The objective of this study was determining of the milling quality of a short-grain Ethiopian rice variety (Selam). A full factorial design was used to study the effects of the parboiling factors in CRD arrangement. The factors were soaking temperatures (40, 60, and 80°C), soaking times (6, 12, and 24 hours), and steaming times (15, 25, and 35 minutes) compared with the non-parboiled rice as a control using controlled randomized design. The result showed that combinations of treatments had significant (P ≤ 0.05) differences in the quality parameters, such as percentage of broken rice, head rice yield, and total milling recovery during milling, compared to the control. The minimum and maximum percentages of breakage for parboiled rice were 0.95 and 9.30%, which were recorded at soaking temperatures, soaking time, and steaming time of 80°C, 24 hours and 35 minutes, and 40°C, 6 hours, and 15 minutes, respectively, in contrast to the non-parboiled rice (41.73% breakage). The result showed that the highest milling recovery (90.40%) was obtained at 40°C soaking temperature, 6 hours of soaking time, and 15 minutes of steaming time compared to the control (79.30%).