U.S. Department of Agriculture (USDA) scientists and researchers have identified the chemical composition and potential bioavailability of nutritious compounds in a representative group of five colorful rice varieties. These findings could help breeders select for these traits from among 18,000 rice samples, called accessions, at the National Small Grains Collection in Aberdeen, Idaho.
Rice bran, the outer layer of whole grain rice, is a rich source of the phytochemical known as gamma-oryzanol, and of two forms of vitamin E: tocopherols and tocotrienols.
In their studies conducted with five color classes of rice bran—including white, light brown, brown, red and purple/black—researchers discovered red and purple rice brans had higher phenolic and flavonoid concentrations than the lighter-colored rice brans measured. The researchers also identified one purple rice bran variety that was both high in phenolic compounds as well as vitamin E and oryzanols. Vitamin E concentration differed among rice brans but was not associated with bran color.
Whole-grain brown rice contains 15 vitamins and minerals, including B vitamins, potassium, magnesium, and iron—all nutrients the body needs to grow and develop normally. In addition to these essential nutrients, there are bioactive phytochemicals in rice, as well as in other whole grains, vegetables, fruits, beans, nuts, and seeds. Although the role of these plant chemicals in terms of human health has not been proven, a body of evidence suggests that some phytochemicals could be nutritionally beneficial.
The team used analytical methods to determine the profiles of tocopherols, tocotrienols and gamma-oryzanol in white, light brown, brown, red, and purple bran. They found a wide variation in the concentrations of the two forms of vitamin E and of gamma-oryzanol.The team also analyzed other phytochemicals—specifically phenolics and flavonoids—in the same five color classes of bran. Research chemist Ming-Hsuan Chen headed up the studies, at the Agricultural Research Service (ARS) Dale Bumpers National Rice Research Center in Stuttgart, Ark., with study findings published in the Journal of Food Science and in Food Chemistry.
