Submitted to: Plant Foods for Human Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/10/2010
Publication Date: 11/16/2010
Citation: Miller, H.B., Grace, S.C. 2010. Variations in bran carotenoids levels within and between rice subgroups. Plant Foods for Human Nutrition. 65:358-363. Interpretive Summary: Rice is a major grain in the human diet. Carotenoids, which are yellow pigments found in many plants, are valuable antioxidants. Removal of the hull from a rice kernel leaves brown rice which has a higher nutritional value than the usual white rice found in the grocery store. Brown rice has a bran layer which contains most of the nutrients, including carotenoids. The many different varieties of rice are divided into subgroups according to where it is grown. Since little is known about differences in the amount of carotenoids in the different varieties of rice, this study determined the differences in bran carotenoid levels among the five subgroups of rice. Measurements were made by a novel, rapid non-destructive fluorescence quenching method using thirty three rice cultivars. The amount of carotenoids was stable in the rice bran for over 10 years of storage. The most popular rice subgroup in the U.S., tropical japonica, had the lowest levels of carotenoids in the bran. These differences in carotenoid content may open up new opportunities for identifying or breeding rice varieties with higher nutritional value.
Technical Abstract: Rice (Oryza sativa L.) is a major grain in the human diet and carotenoids are valuable antioxidants. However, little is known about varietal differences in the carotenoid contents of the rice bran. The objective of this study is to determine the relative differences in bran carotenoid levels among all the five subgroups of rice. Measurements were made by a novel, rapid non-destructive fluorescence quenching method. Confirmation by HPLC after solvent extraction of the bran indicated that the major carotenoid was lutein. Our data showed that carotenoid levels were stable over 10 years of storage. Of the thirty three cultivars that were surveyed, tropical japonica rice, the most consumed subgroup in the U.S., tended to have the lowest levels of carotenoids in the bran while temperate japonicas had the highest. These differences in carotenoid content may open up new opportunities for identifying or breeding rice varieties with higher nutritional value.