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Molecular Characterization of Barley β-Glucans by Size-Exclusion Chromatography with Multiple-Angle Laser Light Scattering and Other Detectors

¹Research chemists and chemist, respectively, Cereal Products Utilization Research Unit, USDA-ARS, Western Regional Research Center, Albany, CA 94710. Reference to a company or product by the USDA is only for purposes of information and does not imply approval of the product to the exclusion of others which may also be suitable. ²Corresponding author. Phone: 510/559-5693. E-mail: bek@pw.usda.gov

Molecular characteristics were determined for mixed-linkage (1→3) (1→4)-β-D-glucans (β-glucans) extracted from Azhul, Crystal, Waxbar, and Prowashonupana barleys. β-Glucans in extracts (with or without α-amylase, protease, hemicellulase, or xylanase treatment) were separated from other components by high-performance size-exclusion chromatography and detected with multiple-angle laser light scattering, refractive index, and fluorometry following postrefractive index treatment with Calcofluor. Pretreatment of barley with 70% ethanol (80°C, 4 hr) reduced β-glucanase activity by ~20%. Hot-alcohol treatment also reduced β-glucan extraction at 23 and 65°C by 42 and 14%, respectively. Molecular weights of β-glucans in the first water extract were generally higher than in succeeding water and alkali extracts. Weight average molecular weights ranged from 0.44 × 10⁶ to 2.34 × 10⁶ g/mol after α-amylase treatment to remove interfering starch. Interference due to pentosans was not demonstrated using enzyme treatments.