Effects of cultivars, organic cropping management and environment on antioxidants in whole grain rice

Authors: Chen, Ming Hsuan; McClung, Anna

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2015
Publication Date: 7/23/2015
Publication URL: http://handle.nal.usda.gov/10113/61185
Citation: Chen, M., Mcclung, A.M. 2015. Effects of cultivars, organic cropping management and environment on antioxidants in whole grain rice. Cereal Chemistry. 92(4):364-369. DOI.org/10.1094/CCHEM-11-14-0240-R.

Interpretive Summary: Whole grain rice contains lipophilic antioxidants (vitamin E compounds and gamma-oryzanol) and phenolic compounds. These compounds have gained significant attention due to their potential human health benefits. External stresses during the plant growth and development have been reported to induce the accumulation of these compounds. We hypothesized that organic crop production which generally has less soil nutrient availability than conventional farming practices, may result in higher contents of these desirable compounds. The objectives of this study were to quantify the effects of choice of cultivar, type of crop management method used, and growing environment (different production years) on the concentrations of these antioxidants in whole grain rice. Of these three factors, cultivars showed the greatest differences in concentrations of the antioxidant compounds, followed by the growing environment (comparing the two growing seasons), and with crop management method (comparing conventional and organic crops) having the least impact. These results are in agreement with numerous studies in other food products which have shown that organic management does not enhance the nutritional quality. Cultivars that are high in concentrations of these antioxidants were identified, but no one cultivar contained the highest concentration of all antioxidants evaluated. Observing that cultivars differ in these compounds indicates that with further traditional breeding, these antioxidant concentrations in whole grain rice can be improved. This study shows that rice varieties can be chosen that will have high levels of specific antioxidant compounds whether grown under organic or conventional management systems.

Technical Abstract: Whole grain rice contains functional antioxidants such as phenolics, flavonoids (including proanthocyanidins), vitamin E homologues (tocopherols and tocotrienols) and gamma-oryzanol that have positive effects on human health. These antioxidants are secondary metabolites in plants that can be induced under external stress. The objectives of this study were to quantify the effects of cultivars, crop management method, and growing environment on the concentrations of these antioxidants in whole grain rice. Cultivars and environment contributed to a higher percentage of variation in the concentrations of these antioxidants than did crop management method. Cultivars accounted for a greater proportion of the variation than environment for all traits except total tocotrienols and gamma-oryzanol. Cultivars that are high in concentrations of these antioxidants were identified, but no one cultivar contained the highest concentration of all antioxidants evaluated. These cultivar differences indicate that improvement for phytochemical and antioxidant traits can be accomplished through traditional breeding. Because of the limited effect of crop management on these antioxidants, choice of cultivar should be the focus for organic production of whole grain rice high in these antioxidants.