Optimization of Physical Refining to Produce Rice Bran Oil with Light Color and High Oryzanol Content

Crude rice bran oil (RBO) is rich in valuable minor components such as tocotrienols, phytosterols and gamma-oryzanol. These compounds are well preserved during physical refining, but in current industrial practice, RBO is mostly refined chemically because this results in a lighter color. However this process removes most of the gamma-oryzanol. The challenge is to develop a refining process which combines a high gamma-oryzanol retention with the commercially desired light color. A modified physical refining process was developed, consisting of an acid degumming, prebleaching, dewaxing, physical removal of free fatty acids using packed column technology, a modified washing step, conventional bleaching and deodorization. A RBO with acceptable oryzanol retention of 39% had a Lovibond red color value (measured with a 5.25-inch cell) of 2.8, approaching very close the color of a chemically refined RBO (red = 2). At the process step where high (94%) retention of gamma-oryzanol was achieved, a somewhat darker Lovibond red value of 5.2 was obtained.