Location: Cereal Crops Research2011 Annual Report
1a. Objectives (from AD-416)
The overall goal of this project is to improve the quality of high soluble fiber oat cultivars. Specific objectives for the project period: Optimize methodologies for the extraction and analysis of soluble oat fiber components; determine environmental variation in the quantity and quality of ß-glucan as characterized in the first objective in newly developed high ß-glucan cultivars and other oat cultivars; and determine relationships between oil concentration and ß-glucan concentration in segregating crosses for these traits, as to how each affects groat breakage during dehulling.
1b. Approach (from AD-416)
Health benefits derived in humans from the consumption of oats are currently understood to be related to the molecular weight of the soluble fiber component commonly called beta-glucan and the increased viscosity of the gut contents created by high molecular weight beta-glucan. We will develop optimized methodologies for the extraction of beta-glucan in order to evaluate its physical and structural, molecular weight, and viscometric properties. We will collect oats samples, including those from newly developed high soluble fiber cultivars, from replicated plots grown in diverse environments over several years. Then we will use our newly developed methods for the analysis of soluble fiber quality to determine how environment might affect the quality and concentration of beta-glucan, especially in the newly developed high beta-glucan cultivars. Finally, we will test how beta-glucan affects the milling quality of oats. Because beta-glucan is in the cell walls of oats, it is thought to provide a strengthening effect, which reduces groat breakage during dehulling. However, high oil in oats also seems to prevent groat breakage, and currently breeders have been unable to separate the traits of high oil and high beta-glucan in oats. A collaborating genetics program has developed populations of recombinant inbred lines from oat crosses designed to be segregating for high oil and high beta-glucan. We will evaluate the phenotypes of these lines and test their behavior during dehulling to determine the relative roles of oil and beta-glucan in preventing groat breakage during oat milling.
3. Progress Report
A new project on the characterization of beta-glucan quality in oats was initiated. Initial experiments centered on the optimization of beta-glucan extraction for analytical purposes. The simplest approaches have proved to be the best. We found that temperature and pH had very little effect on beta-glucan extraction, as long as sufficient time was allowed for the extraction (e.g. 18 hrs) and that enzymes had been sufficiently inactivated in the flour. Addition of external hydrolytic enzymes to digest possible contaminants invariably led to the degradation of beta-glucan polymer. Flour to water ratio of 2 g of flour to 50 mL proved best for extraction of beta-glucan for analytical purposes. For viscosity experiments, we found 8 g of flour per 50 mL water provided solutions saturated with high molecular weight beta-glucan. Addition of hydrolytic enzymes or insufficient inactivation of endogenous hydrolytic enzymes led to more efficient extraction, but solutions contained polymers with much lower molecular weights. Because high molecular weight and high viscosity are considered positive quality characteristics, our simple extraction appeared best suited for analysis of beta-glucan quality. The most effective methods for enzyme inactivation appeared to involve high temperature steam (106 to 130 degrees C). Viscosity experiments along with molecular weight determinations using multi angle laser light scattering indicated that steam treatments changed the configuration of the beta-glucan relative to dry heat treatments. Steam heat increased intrinsic viscosity of solutions relative to toasted samples (dry heat) without affecting the molecular weight of the polymer. We have also determined significant differences in extractability of beta-glucan and in the fine structure of polymer according to genotype and environment.
1. Standardized extraction of beta-glucan. Beta-glucan is a soluble fiber in oats that improves heart health in humans by decreasing serum cholesterol. Since the development of high beta-glucan oat cultivars, the quality of the beta-glucan derived from cultivars grown in different locations and environments has come into question. ARS Researchers in Fargo, ND, developed a standardized extraction protocol for quality analyses for beta-glucan. They demonstrated the importance of hydrothermal treatments for the inactivation of endogenous beta-glucanase activity and that externally applied hydrolytic enzymes, designed to hydrolyze contaminating compounds extracted with the beta-glucan, also degraded beta-glucan. The simple water extraction of oat flour from grain exposed to 106 degrees C steam provides a means to evaluate the quality of beta-glucan from any oat grain. This provides standardized protocols for industry to evaluate beta-glucan quality in oat lots.
2. Environment affects beta-glucan. A major reason that people eat oats is because the soluble fiber or beta-glucan in oats will lower cholesterol and improve heart health. ARS Researchers in Fargo, ND, in collaboration with North Dakota State University, have developed oat cultivars high in beta-glucan, but it has never been clear how environment affects the beta-glucan. Recent results from Fargo ARS and North Dakota State University laboratories have shown that drier environments produce oats with lower beta-glucan concentration and that the molecular structure of the beta-glucan has been changed in subtle ways. This information will help oat companies source their oats more appropriately to their needs.Doehlert, D.C., Angelikousis, S., Vick, B.A. 2010. Accumulation of Oxygenated Fatty Acids in Oat Lipids During Storage. Cereal Chemistry. 87(6):532–537.