A new study has suggested that rice bran extracts – such as antioxidant phytochemicals – could be used to prevent lipid and protein oxidation in foods, and consequently, preserve their nutritional and functional properties in foods. The research, published in the Journal of Food Science, claims to provide a foundation for those interested in utilizing or improving specific rice varieties for their health benefits.
“The variation in phyotochemical concentrations and composition among the studied pigmented-bran rice varieties indicates the potential to breed for future varieties containing benefits for various nutraceutical and functional food developments,” wrote the researchers, led by Byungrok Min from the University of Maryland, in conjunction with the Department of Agriculture.
Rice bran is a by-product of the rice milling process that has potential as a rich source of valuable health-promoting compounds. It accounts for approximately 10 percent of brown rice by weight.
The health-promoting compounds of bran include phytochemicals – antioxidants linked with health benefits such as a reduced incidence of chronic diseases, and certain inflammatory diseases.
The majority of rice varieties grown around the world have light-brown bran, said the authors. Therefore, phytochemical studies have primarily been focused on the bran of light-brown color, and specifically on the lipophilic antioxidants, such as vitamin E (including all of the 8 naturally occurring forms – alpha, beta, gamma, and delta –of both tocotrienols and tocopherols) and gamma-oryzanols.
Min and colleagues noted that these lipophilic phytochemicals are potent antioxidants that have shown various health-beneficial effects, including the prevention of cancer and cardiovascular disease, as well as reduction of oxidative damage in food.
Therefore, they claim that rice bran oil should be an attractive source for functional-food applications, when compared to plant-derived oil.
The lipophilic antioxidants extracted from light brown-colored rice may also have a potential chemo-preventative effect.
“Thus, rice bran and its extract have potential application as health-promoting ingredients in functional foods. In addition, with increasing concern about the safety of synthetic antioxidant usage, there has been increasing interest in the use of natural antioxidants from plant extracts as an alternative,” said the researchers.
“We evaluated the potential of colored rice bran and its extract as unique sources of phytochemicals for food applications by comparing these phytochemical profiles and antioxidant capacities with those of blueberry and broccoli, which are well established as sources rich in phytochemicals,” they added
In general, the concentrations of lipophilic antioxidants of vitamin E (tocopherol and tocotrienols) and gamma-oryzanols were not found to be associated with bran color.
The researchers demonstrated the uniqueness of red and purple rice brans in containing both lipophilic and polyphenol antioxidants. They added that the two brans also had significantly higher total phenolic and total flavonoid, as well as higher total antioxidant activity compared to blueberry or broccoli.
Total proanthocyanidin concentration was also reported to be the highest in red rice bran, while total anthocyanin was highest in purple brans.
“These results indicate that rice brans are natural sources of hydrophilic and lipophilic phytochemicals for use in quality control of various food systems as well as for nutraceutical and functional food application,” concluded the researchers
Because red and purple rice bran contains high concentrations of both hydrophilic and lipophilic phytochemicals, Min and colleagues suggested that they could be suitable as natural preservatives in various food systems, where either hydrophilic or lipophilic conditions are dominated. In addition, they noted that red and purple rice brans are also great natural sources of proanthocyanidins and anthocyanins, which may have additional health benefits.
Source: Journal of Food Science
Published online ahead of print, doi: 10.1111/j.1750-3841.2010.01929.x
“Phytochemicals and Antioxidant Capacities in Rice Brans of Different Color”
Authors: B. Min, A.M. McClung, M.H. Chen