Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2015
Publication Date: 6/22/2015
Citation: Yadav, M.P., Hicks, K.B. 2015. Isolation of barley hulls and straws constituents and study of emulsifying properties of their arabinoxylans. Carbohydrate Polymers. 132:529-536.
Interpretive Summary: Previous studies in our lab have reported a method to produce a potentially useful food additive called Corn Fiber Gum (CFG). In this case, the word “gum” does not mean that this material would be used as a chewing “gum”, but rather as a food ingredient composed of complex carbohydrates that can serve as an emulsifier of oil-in-water. The U. S. beverage industry uses hundreds of tons of high quality emulsifiers each year for stabilizing citrus oil in soft drinks and for preventing the separation of oil and water in salad dressings plus hundreds of other applications. The most commonly used emulsifier, “gum arabic” is an imported gum that is expensive and is often in short supply due to political and environmental issues in the African countries of origin. To solve this problem, we previously extracted and purified a new type of “gum” called “corn fiber gum (CFG)” from an abundant and inexpensive byproduct of corn processing called “corn fiber. A similar bio-based fiber gum can also be prepared from another low-value by product, “barley hulls” and “barley straw” obtained from barley producing regions. This gum can be called “Barley Fiber Gum” (BFG). In addition to BFG, other valuable carbohydrate components may also be obtained from the same source for other applications. Because the gum from corn fiber was a good emulsifier, we decided to see if that was the case for these new barley fiber gums. In this study we found for the first time that BFG from barley straws are as good as CFG for stabilizing flavor in oil-in-water emulsion system. We also found that easily extractable water soluble carbohydrate is also present in high amount in barley straw, and that this material could be used as a feedstock for fuel ethanol production. Another important carbohydrate polymer is also present in high yield in barley straws, which will be tested for making bio-degradable packaging materials. These results will benefit U.S. barley processors and barley farmers by increasing the value of their low value by-products.
Technical Abstract: Barley hulls (husks) are potential by-products of barley ethanol production. Barley straw is an abundant biomass in the regions producing barley for malting, feeds, and fuel ethanol. Both barley hulls and straw contain valuable arabinoxylans and other useful carbohydrate and non-carbohydrate components. To characterize all the components of barley hulls and straw, they were treated with hot water to obtain water extractable materials and with a-amylase to remove starch. The main functional component, water soluble non-caloric arabinoxylan was then isolated from hot water-extracted and de-starched barley hulls/straws by an alkaline hydrogen peroxide extraction followed by ethanol precipitation. The oligosaccharides, acid insoluble lignin and other acid soluble components present in the supernatant after arabinoxylan precipitation were also obtained. The sugar composition of the arabinoxylans showed that they were typical arabinoxylans containing (in addition to arabinose and xylose) some galactose, glucose and acidic sugars in the side chains. The acid-soluble arabinoxylans (hemicellulose B fractions) from barley straws were superior oil-in-water emulsifiers than those from barley hulls.