Stabilized Rice Bran and Its Application in Analog Rice Formulation

Abstract

Indonesian rice consumption is one of the largest one in the world. This condition has raised concern to from the government. They issued Presidential Decree No. 22 in 2009 aims accelerate food diversification progam based on local resources. The development of analog rice can be one alternative to support food diversification program. Extrusion technology is used in manufacturing process of analog rice. This technology enables to formulate rice with various compositions and also makes product preparation and development easier. Corn flour, sago, soy flour, and rice bran are local resources used for analog rice. Corn flour, soy flour, and sago were used because these raw materials have been very common for Indonesian society, therefore analog rice resulted in this study was expected to be easily accepted in Indonesia. Corn flour was used because it has higher dietary fiber than wheat. Soy flour was used as a source of protein. The presence of protein increases the nutritional value and improves the texture of the analog rice. Other raw material of analog rice is sago. Sago is one of the primary food in East Indonesia. Rice bran contains high dietary fiber and has good antioxidant activity. Rice bran contains tocopherol (vitamin E), tocotrienols and oryzanol that have antioxidant capacity. Rice bran also has low glycemic index. Rice bran is a by-product of rice mill. It is a thin layer covering the rice seeds after husk removal. Rice bran must be stabilized immediately upon production to protect it from lipase activity, which can reduce quality of the rice bran by stimulating off flavor formation. Many methods have been developed to deactivate the lipase in rice bran. However, those methods are difficult to operate and they require a lot of energy so that less suitable for small rice milling unit. Therefore in this study, we developed another stabilization method by using single screw conveyor. The initial study was undertaken to determine the effects of stabilization treatment by using a single screw conveyor to the content of free fatty acids and bioactive components (α-tocopherol and ϒ-oryzanol) of rice bran. The treatments used were A100 (screw speed of 15 Hz, 100 °C), A120 (screw speed of 15 Hz, 120 °C), A140 (screw speed of 15 Hz, 140 °C), B100 (screw speed of 25 Hz, 100 °C), B120 (screw speed of 25 Hz, 120 °C), and B140 (screw speed of 25 Hz, 140 °C). It was shown that rice bran stabilization by using screw conveyor was able to significantly suppress an increase of FFA content of stabilized rice bran as compared to control (unstabilized one). Particularly, A120 was the best treatment for preventing rancidity (FFA content <10%) with a minimum decrease in α-tocopherol and γ-oryzanol content. It can be concluded that single screw conveyor is potential to be used in small-medium scale rice milling unit to produce rice bran with better self-life, while the nutrition content can be preserved. 6 The stabilized rice bran obtained from the most optimum condition was used in analog rice formulation using Mixture Design in Design Expert program (DX7). Mixture Design in the Design Expert v 7.0 (DX7) is a program used to obtain the most optimum formula for the studied product. In this study determination of the best formula was based on the lightness and antioxidant activity of analog rice as two responses. The most optimum formula obtained from DX7 progam consisted of 32.17% corn flour, sago 16.67%, 13.3% soybean flour, 3.16% rice bran, and 1.33% GMS (with water content of 50% of the dry dough). The analog rice was characterized and compared with the milled rice and Beras Cerdas. This study obtained protein content of analog rice was higher than milled rice and Beras Cerdas (11.4%) while dietary fiber in analog rice was as high as 13.3% (>6%). Results of sensory analysis showed that both analog rice and Beras Cerdas had a score of neither like nor dislike-like slightly (Analog rice score was 4.97 and Beras Cerdas 4.90). Glycemic index test was then performed for the resulted analog rice. It was based on Ethical Approval No. LB 02.01/5.2/KE.209/2013 issued by the Ethics Commission of the Ministry of Health of Indonesia. Based on the data obtained, it showed that the glycemic index of the optimum analog rice was 54 ± 18. Based on the results of analog rice characterizations, this study has resulted analog rice formulation from corn flour, sago, soy flour, and rice bran, with high protein and dietaryfiber. The results of this study indicate that analog rice is potential to be developed as functional food products based on local resources.