The typical composition of crude rice bran oil is 81.3-84.3% triglycerides, 2-3% diglycerides, 5-6% monoglycerides, 2-3% free fatty acids, 0.3% waxes, 0.8% glycolipids, 1.6% phospholipids, 4% unsaponifiables. In comparison with other vegetable oils, crude rice bran oil tends to contain higher levels of non-triglyceride components, most of which are removed during further refining processes. The free fatty acids, monoglycerides and diglycerides in rice bran oil are associated with enzymatic hydrolysis. The phospholispids predominantly include phosphatidylcholine, phosphatidylethanaolamine, and phosphatidylinositol. The wax content of rice bran oil can be somewhat variable, depending upon cultivar and processing parameters. Various sterols constitute the principal portion of the unsaponifiable fraction of nutraceutical interest. In recent years, many studies have been conducted in the area of utilization of these minor components as co-products of rice bran oil processing.

Table 1 compares the fatty-acid composition of rice bran oil with that of peanut, soybean, and cottonseed oils.

Fatty acid (%) Percentage Rice bran Percentage Peanut Percentage Soybean Percentage Cottonseed
Myristic (14:0) 0.2 0 0.2 0.8
Palmitic (16:0) 15.0 8.1 10.7 27.3
Stearic (18:0) 1.9 1.5 3.9 2.0
Oleic (18:1) 42.5 49.9 22.8 18.3
Linoleic (18:2) 39.1 35.4 50.8 50.5
Linolenic (18:3) 1.1 0 6.8 0
Arachidic (20:0) 0.5 1.1 0.2 0.3
Behenic (22:0) 0.2 2.1 0.1 0

Table 1. Fatty-acid composition of selected oils. From Young (1996), Sipos and Szuhaj (1996), and Jones and King (1996). Data for rice bran oil are from Riceland Foods, Inc.

Oleic and linoleic fatty acids constitute more than 80% of the fatty acids of the glycerides. Rice bran oil is similar to peanut oil in fatty acid composition with a saturation level that is slightly higher than that of conventional soybean oil. The much lower linolenic acid content of rice bran oil makes it more stable to oxidation than soy oil.

The quality characteristics of properly refined rice bran oil include a maximum free fatty acid levels (as oleic acid) of 0.1%, a maximum peroxide value of 1.0 meq/kg, 0.05% moisture, an iodine value of 99–108, saponification value of 180-195, and a Lovibond color value of 3.5R. Appearance of rice bran oil ranges from cloudy to clear depending on the degree of dewaxing and winterization processes applied.