Utilization of rice bran for manufacturing nutritional and functional food ingredients

• Main Authors: Wea-Shyang Fuh, 傅偉祥
• Other Authors: Been-Huang Chiang, Ph. D.
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/95620585399812739275

博士 === 國立臺灣大學 === 食品科技研究所 === 89 === Abstract During milling processes, approximately 10% rice bran is removed from the brown rice to yield milled rice. Rice bran is an unstable material, but can be stabilized by the high temperature short time extrusion process. Result of this study showed that stabilization of rice bran could be achieved by extrusion at 130°C and screw speed of 140 rpm for 20 seconds. The extruded rice bran can be stored at room temperature for at least 20 days without showing significant change in acid value. Removal of phytic acid from the rice bran was studied using two methods, the solvent extraction method and the enzyme hydrolysis methods. Nearly 94% of phytic acid in the extruded rice bran could be removed by extraction conducted at 25°C for 30 min using hydrochloric acid at pH 2 as solvent and at a solvent to rice bran ratio of 15. After the extract was neutralized and phytic acid removed, it was added back to the rice bran solid to replenish the nutritional and functional components of the solids. The mixture was dried with a drum dryer to obtain a powdered product. This processing procedure preserved most of the nutritional components in the rice bran, but approximately 50% of oryzanol that originally existed in the rice bran lost during processes. Phytic acid can be hydrolyzed by the phytase co-existing in the rice bran, and addition of acetate buffer (pH 5.5) in fresh rice bran could activate the phytase. When the fresh rice bran was mixed with acetate buffer of pH 5 with a ratio of 1:2.5 (w/w), then the mixture was incubated at 55°C for 12 h, approximately 40 – 60 % of phytic acid was hydrolyzed. Addition of 0.1% of cellulase to the mixture increased the degree of hydrolysis to 80 – 88 %. The germinating seeds contain active phytase, which can be used for phytic acid hydrolysis. The highest phytase activity was detected after 120 hours of seed germination. By mixing equal amounts of dehydrated germinating seed powder, either wheat or barley, with extruded rice bran, then incubated at 55 °C for 12 hours in acetate buffer at pH 5.5, more than 90% of phytic acid in the rice bran was hydrolyzed. The process also preserved most of the nutritional components in both of the rice bran and the seeds. However, approximately 40 – 50 % of oryzanol lost during enzymatic hydrolysis.