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Title: Heat-stability of health-beneficial phytonutrients/antioxidants in rice

item Chen, Ming Hsuan

Submitted to: Texas Experiment Station Field Day Handout
Publication Type: Experiment Station
Publication Acceptance Date: 7/6/2010
Publication Date: 7/8/2010
Citation: Chen, M. 2010. Heat-stability of health-beneficial phytonutrients/antioxidants in rice. Texas Experiment Station Field Day Handout.

Interpretive Summary:

Technical Abstract: The consumption of whole grain has been linked to the reduced incidence of chronic (cancer, diabetes, cardiovascular disease) and various inflammatory diseases. The phytonutrients/antioxidants contained in the whole grain, specifically in the bran layer, contribute to these health benefits. Rice bran is a rich source of lipophilic antioxidants, including vitamin Es and '-oryzanols. In addition, the phenols extracted from light brown colored rice have a potential chemopreventive effect. Recent interest has also been focused on pigmented rice, and especially on the purple and red colored bran rice cultivars because of their abundance of anthocyanins and tannins, respectively. The objective of this study was to investigate the effect of steam-cooking and parboiling on the concentrations of antioxidants (vitamin Es, '-oryzanols and flavonoids) and antioxidant capacities of pigmented, i.e., red and purple, and common light brown bran rice. The cooking processes included whole-grain steam-cooked (S), paddy (with hull) parboiled (PP), and parboiled paddy steam-cooked (PP-S). Uncooked whole-grain (Raw) served as a control. The concentrations of total vitamin Es (sum of tocopherols and tocotrienols) and '-oryzanols varied among three cultivars. In relation to Raw, the uncooked control, these lipophilic antioxidants were fairly heat-stable across all the cooking methods or the combination of cooking methods (Fig.1a and 1b). For the total flavonoid concentration, the Raw light brown bran rice contained less than one sixth that ofred and purple bran rice, but the flavonoids in the light brown bran rice were heat-stable (Fig. 2a). The flavonoids in the red bran rice were very heat-sensitive: S reduced the flavonoid concentration to 45% of Raw; PP-S reduced it to 21% of Raw. Nevertheless, PP-S-red bran rice still contained 1.8 times more flavonoids than PP-S light brown bran rice. Relative to red bran rice, purple bran rice contained a high concentration of heat-stable flavonoids. The concentrations of total flavonoids of S- and PP-purple rice were retained at 97% and 92% of Raw, respectively; while PP-S-purple rice was retained at 65%. The PP-S-purple rice contained 5-fold higher total flavonoid concentration than light brown rice. Similar patterns as seen for total flavonoid concentration were observed for the antioxidant capacities of these samples (Fig. 2b). The results clearly demonstrated that different types of flavonoids and antioxidants were present among rices of different bran color. Rice cultivars with a high concentration of heat-stable antioxidants would have great potential for use in snack bars and cereals, in addition to being consumed as steam-cooked table rice. For questions please contact: Other scientist s involved in this project: Drs.Byungrok Min and Anna McClung.