Impact of Parboiling on some Characteristics of Rice (Champa Variety)

Abstract

Introduction Rice is one of the most important cereal grains in the world. Milling is one of the most important phases of the paddy processing that affects the quality and quantity of the product. Postharvest losses include threshing, drying, transportation and milling contains about 30–40% of total produced rice in developing country. Parboiling increases the mailing efficiency of rice from 51% to 80%, protein, fat and ash content. Champa variety is one of the most important varieties of rice in the southwest of Iran and has low milling quality in spite of its flavor and aroma. This study was conducted to assess increasing the quality of Champa rice milling phase by parboiling method. Materials and Methods This study was conducted to‏ assess the increasing quality of Champa rice milling phase by parboiling method in the growing season of 2016 in Lordegan city. Paddies were prepared from a rice farm in Lordegan city. Parboiling treatments consisted of three soaking temperatures (35, 55 and 75 °C) and two steaming times (15 and 25 minutes) at a steam temperature of 110 °C. This study was performed in a factorial experiment based on a completely randomized design in three replications. Parboiling process included soaking, steaming, drying and whitening. Bain Marie was used to keep the water temperature constant in two phases of soaking and steaming. Samples were placed in a oven to decrease the humidity in the drying phase. Breakage percentage, loss of solid material, milling efficiency, whiteness degree and the ratio of length to width were measured in raw and baked rice in all samples. Results and Discussion Breakage in control treatment (non-parboiling) was 19.38%. The lowest breakage percentage (4.03%) was obtained in parboiling treatment (soaking temperature of 55 °C and a steaming time of 15 minutes). Parboiling improved milling efficiency and reduced loss of solid materials. Highest milling efficiency (67.11%) was obtained in a soaking temperature of 55 °C and steaming time of 25 minutes. The lowest amount of loss of solid materials (1.74%) was obtained in a soaking temperature of 75 °C and steaming time of 25 minutes. The highest ratio of length to width (2.46) and the highest whiteness degree (76.54%) was obtained in no parboiling treatment. There was no significant difference in water absorption parameter between parboiling treatment and non-parboiling treatment. Conclusions Champa rice variety has a very good flavor and aroma but did not have good appearance and its breakage percentage is not good. Parboiling reduces the breakage and improves the appearance in raw and baked rice. Parboiling had a lot of positive effects on the milling quality of this rice cultivar. The best treatment (soaking temperature of 55 °C and steaming time of 25 minutes) reduced breakage percentage (by 79%) and loss of solid materials (by 37%) and increased milling efficiency (by 2%) in comparison with control treatment (non-parboiling). Overall, parboiling reduced rice streaking during baking by improving the quality attributes of paddies and finally improved the rice shape.

Keywords

• champa rice
• parboiling
• rice breakage percentage
• milling efficiency
• polishing degre