Location: Cereal Crops Research2013 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:
Oats (Avena sativa L.) contain a soluble fiber commonly called beta glucan to which health benefits have been attributed. Effects of oat plant genotype and environment on beta glucan extractability, flour slurry viscosity, and beta glucan polymer fine structure were investigated. Environment had a strong effect on beta glucan extractability, whereas genotype had no significant effect. However, oats grown in drier environments and cultivars with higher beta glucan content have beta glucan with fine structure differences (relative to oats grown in wetter environments or with lower beta glucan content) that influence extractability of beta glucan. The observed variations may influence functional properties, such as viscosity or potential health benefits. Extraction protocols for beta glucan from oat flour were tested to determine optimal conditions for beta glucan quality testing, which included extractability and molecular weight. Mass yields of beta glucan were constant at all temperatures, pH values, and flour-to-water ratios, as long as sufficient time and enough repeat extractions were performed and no hydrolytic enzymes were present. Extracts contained about 30–60% beta glucan, with lower proportions associated with higher extraction temperatures in which more starch and protein were extracted. All commercial starch hydrolytic enzymes tested, even those that are considered homogeneous, degraded apparent molecular weight of beta glucan as evaluated by size exclusion chromatography. Higher concentration beta glucan solutions could be prepared by controlling the flour-to-water ratio in extractions. Optimal conditions were determined that generated the highest native beta glucan concentrations.