2009 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.
All objectives proposed for the original five year project were completed. The original approach proposed in the first objective for the investigation into the physical basis of high test weight turned out to be unproductive, but contingency plans resulted in highly significant findings on the roles of kernel density and kernel packing efficiency in the control of test weight and new technology developed allowed for many novel findings. Included with data from the second objective, we established theoretical and empirical relationships between oat test weight and groat proportion. The second objective on oat dehulling was completed, largely as described in the original proposal and the results have been written into three manuscripts, one of which is published, the other two are still in review. The third objective was confounded by the discovery of a diversity of glycolipids, never before observed in any living system. It was necessary to recruit collaborators with expertise in LC-MS and MS-MS to identify these novel glycolipids, which turned out to be estolides of galactosyl diglycerides, where glycolipids containing one, two, three and four galactose moieties were esterified to a glycerol group with two other fatty acids, as in a normal galactolipid, but with one, two, and three extra fatty acids attached to at least one of the backbone fatty acids, sometimes in a daisy chain like configuration. Most of these compounds had never been described before.
Mechanisms of Green Color Appearance in Cooked Oats: Occasionally oat companies will receive complaints from consumers that their oats (steel cut groats) turned green when they were cooked in tap water; this problem has been particularly puzzling because no pigments are found in oat grain. ARS scientists in Fargo, ND investigated several possibilities, and concluded that the problem is probably derived from iron in well water, which may contain high concentrations of ferrous ion (Fe+2). The aleurone layer of steel cut groats turned a greenish brown color when cooked in water with 50 ppm ferrous ion. Fortunately, ferrous ion is not stable in the presence of oxygen and rapidly oxidized to the water insoluble ferric ion (Fe+3). Thus, the color can only appear in freshly pumped well water, and if the water is allowed to stand for several hours, the iron will oxidize, precipitate and settle to the bottom of a holding tank. Phenolic compounds in oats will turn a yellowish green color under alkaline conditions (above pH 9.0), but these conditions are more likely to occur in industrial processes rather than in the home.
Genotypic and Environmental Effects on Oat Dehulling Characteristics: The economic yield of a load of oats to an oat processor is largely dependent on the yields they receive after the dehulling process. ARS scientists in Fargo, ND used an industrial sized impact oat dehuller to dehull eighteen different oat cultivars grown in six diverse environments. Our results determined that test weight and especially kernel density were the most important factors associated with enhanced yields. Sources of error in the determination of groat proportion, which is particularly important in the determination of oat quality, were also determined. Aspiration associated with any mechanical dehulling mechanism always removes significant amounts of groats, thus under estimating groat proportion. Results indicate which oats will provide the best yields and provides several approaches to most accurately measure groat proportion.
5.Significant Activities that Support Special Target Populations
Oats are more commonly grown by smaller farms. This project contributes to the development and release of new oat cultivars through the North Dakota State University Oat Improvement Program. We have been particularly active in the selection of high fiber cultivars, such as “HiFi”, which provide greater health benefits to consumers and more value to the producers.
Doehlert, D.C., Mcmullen, M.S. 2008. Oat Grain Density and the Physical Basis of Test Weight. Cereal Chemistry. 85 (5): 654-659.
Doehlert, D.C., Ohm, J., Mcmullen, M.S., Riverland, N.R. 2008. Theoretical and Empirical Relationships between Oat Test Weight and Groat Proportion. Cereal Chemistry. Vol 86 (2) 239:246
Doehlert, D.C., Simsek, S., Wise, M.L. 2009. The Green Oat Story: Possible Mechanisms of Green Color Formation in Oat Products During Cooking Color Changes in Cooked Oat Products. Journal of Food Science. 74(6):S226-S231
Wise, M.L., Doehlert, D.C., Mcmullen, M.S. 2008. Association of Avenanthramide Concentration in Oat (Avena sativa) Grain with Crown Rust Incidence and Genetic Resistence. Cereal Chemistry. 85(5)639-641.