2010 Annual Report
1a.Objectives (from AD-416)
To contribute to the improvement of oat quality by characterizing panicle and kernel structure characteristics associated with environmental stability of high test weight, by determining kernel structure characteristics associated with improved milling yield, and by the characterization of genotypic and environmental effects on the chemical composition of polar lipids in oat groats.
1b.Approach (from AD-416)
In order to determine panicle and kernel structure effects on environmental stability of test weight, fifty advanced lines of oats will be selected from an oat breeding program in North Dakota. Selected lines will have high potential for high test weight and will be highly variable for panicle size. Lines will be grown in four diverse environments and intact panicles will be harvested. Panicle and kernel size and structure will be analyzed along with test weight to determine physical characteristics that provide high test weight even in harsh environments that adversely affect yield. Kernel structure associated with improved milling yield will be determined by dehulling different genotypes of oats with an impact dehuller, similar to dehullers used by industry. Every oats sample will be fractionated by kernel size by three different mechanisms that divide according to different size characteristics. Slotted sieves will separate according to kernel width, disc separators will separate according to kernel length, and a gravity table will separate according to kernel density. Each size fraction will be dehulled at a
series of dehuller rotor speeds, so that the influence of different kernel size characteristics on dehulling efficiency and milling yield can be determined. Finally, oat polar lipids will be characterized from a variety of oat cultivars grown in diverse environments. Polar oat lipids will be extracted and analyzed for their chemical composition by chloroform/methanol/water extraction, separation by
silica gel chromatography, and analyzed by high pressure liquid chromatography using an evaporative light scattering detector.
This bridging project was initiated in July 2009 after the previous project 5442-21440-004-00D expired. Manuscripts from the previous project were completed and the project plan for a new project was written and approved after OSQR review with minor revisions. The new project 5442-21440-006-00D was implemented in June 2010. New research on definitions of beta-glucan quality in oats has been initiated.
Optimal conditions for beta-glucan extraction have been established after a series of systematic analyses. Analysis of 18 oat genotypes grown in 6 different environments indicated no significant genotypic difference in beta-glucan solubility, but large and significant differences in beta-glucan solubility among environments were found. A manuscript is being prepared and should be ready for the approval process soon. We continue systematic extractions of beta-glucan from eight oat genotypes with diverse beta-glucan accumulation potential grown in seven locations each year to determine how environment affects beta-glucan quality, as indicated in the recently approved project plan.
A final paper on lipid chemistry, addressed in the previous project, concerning identity and accumulation of oxygenated fatty acids in oats during storage is being prepared, largely from old data, only recently confirmed. These oxygenated fatty acids are very bitter in flavor and detract strongly from the quality of stored oat products.
A survey of the chemical composition of 18 oat genotypes from 6 environments is being completed. Most of the composition data had been gathered as part of the previous project, but is now being compiled, along with some addition analyses to provide a comprehensive work on oat composition. Mineral composition is being provided by collaboration with the University of Saskatchewan, in Saskatoon, Canada. This will provide a general reference on oat composition, not readily available in current literature.
Collaborative work on the stability of oat beta-glucan molecular mass after extraction is being conducted with laboratories at North Dakota University, Purdue University, and the University of Helsinki in Finland. Analyses include rheological analyses, analytical centrifugation, and size exclusion chromatography with molecular mass determined by multi-angle laser light scattering detection.
Oxygenated fatty acids in oat lipids. ARS researchers in Fargo, ND, have identified seven oxygenated fatty acids in oat lipids by gas chromatography-mass spectrometry, including three hydroxy fatty acids and four epoxy fatty acids. Of these, all but one (a 15-hydroxy fatty acid) are involved in fat rancidity in oats. They have followed their accumulation in oat groats and oat flour during a 22 week storage treatment and have found that steam pretreatment of oats before storage greatly decreased the amount of hydroxy and epoxy fatty acids, apparently because of enzyme inactivation induced by the steam treatment. Also more oxygenated fatty acids accumulated in oat flour than in oat groats. Oxygenated fatty acids are known to detract from the quality of oat products because of the bitter tastes associated with them. Information from this study identified the products from oat lipid oxidation, and indicates how storage conditions affect their accumulation to allow better treatment of oat products by the food industry.
Polar Lipids in Oats. Quantitative analysis of polar lipid from oat kernels, conducted by ARS scientists in Fargo, ND, indicated that oats may be the richest source of polar lipids among any plant source, at least according to current literature. Over 2% of the oat dry mass is composed of either phospholipid or glycolipid, which are the two main types of polar lipids. About 60% of the polar lipid is glycolipid, which includes di, tri, and tetra galactosyl diglycerides, along with a variety of estolides, where additional fatty acids are hooked on to the glycolipids. This work has contributed to product development by a small company in the United States.
Doehlert, D.C., Wiesenborn, D.L., Mcmullen, M.S., Ohm, J., Riveland, N.R. 2009. Effects of Impact Dehuller Rotor Speed on Dehulling Characteristics of Diverse Oat Genotypes Grown in Different Environments. Cereal Chemistry. 86(6): 653-660
Doehlert, D.C., Mcmullen, M.S., Riveland, N.R. 2010. Groat Proportion in Oats as Measured by Different Methods: Analysis of Oats Resistant to Dehulling and Sources of Error in Mechanical Dehulling. Canadian Journal of Plant Science. 90: 391-397