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United States Department of Agriculture

Agricultural Research Service

Title: Macromolecular Characterisation of Three Barley Beta-Glucan Standards by Size-Exclusion Chromatography Combined with Light Scattering and Viscometry: An Interlaboratory Study.

item Christensen, B - NORWEGIAN UNIV SCI & TECH
item Knuckles, Benny
item Williams, D - EAST TENN. STATE UNIV.
item Fishman, Marshall
item Chau, Hoa
item Wood, P - AG & AGRI-FOOD CANADA

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 10, 2000
Publication Date: April 10, 2000

Interpretive Summary: Beta-glucan is a polysaccharide found in barley and oats. It is a soluble food fiber which has been found to lower blood cholesterol, glucose and insulin levels. The mechanisms by which it affects these levels is not well understood. Rapid, accurate characterization of molecular properties is necessary to establish how the structure of Beta-glucan is related to its function as a food fiber. In this interlaboratory study on Beta-glucan standards, it was shown that size exclusion chromatography with on-line molecular weight, size and viscosity detectors could be used to rapidly and accurately determine the overall molecular structure of Beta-glucan. This research will aid in a better understanding of how a major constituent of barley and oats functions as a nutrient in preventing heart disease and diabetes. Therefore it is of interest to producers of barley and oats and to consumers.

Technical Abstract: Beta-glucan standards (A-F) isolated from barley were analyzed by size- exclusion chromatography (SEC) in five different laboratories with varying columns, solvent conditions and detector systems (low- and multi-angle light scattering and viscometry). Static (batch) measurements by capillary viscometry and laser light scattering were included. Fairly consistent results were obtained for the weight average molecular weights, M(weight), radii of gyration and intrinsic viscosities, demonstrating that the Beta- glucans may serve as useful standards or reference materials in the study of cereal Beta-glucans. Average values for M(weight) were: A,E: 114,000 (plus or minus 11%), B,C: 374,000 (plus or minus 9%), D,F: 228,000 (plus or minus 13%). Some inconsistencies regarding the polydispersity, M(weight)/M(number), could be ascribed to the influence of peak broadening in certain column/solvent systems. The study further demonstrated that individual researchers tended to use different processing parameters, especially refractive index increments (dn/dc), due to ambiguities in the literature or to differing experimental values. The need for consistent parameters and processing methods is clearly demonstrated.

Last Modified: 5/5/2015
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