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Rheological Properties of (1→3),(1→4)-β-D-Glucans from Raw, Roasted, and Steamed Oat Groats

¹Graduate assistant and associate professor respectively, Department of Cereal Science, Harris Hall, North Dakota State University, Fargo, ND 58105. ²Current address: The Kellogg Company, W. K. Kellogg Institute for Food and Nutrition Research, 2 Hamblin Avenue East, Battle Creek, MI 49016-3232. ³Research chemist, USDA-ARS Hard Red Spring and Durum Wheat Quality Laboratory, Harris Hall, North Dakota State University, Fargo, ND 58105. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ⁴Corresponding author. E-mail: doehlert@plains.nodak.edu

Effects of hydrothermal treatments (steaming, roasting) of oat grain on β-glucan extractability and rheological properties were tested on oat cultivars with low (Robert) and high (Marion) β-glucan content. Steaming of grain reduced the amount of β-glucan that could be extracted, compared with raw or roasted grain, but the extracts from steamed grain had much greater viscosity. Increased extraction temperatures increased the amount and the average relative molecular mass (M _r) value of β-glucan extracted. In boiling water extractions, the average M _r values among raw, roasted and steamed oat samples were equivalent, but extracts from steamed oat grain had significantly higher intrinsic viscosity than the extracts from roasted or raw oat grains. β-glucan solutions purified from steamed grain extracts were very viscous and highly pseudoplastic, as described by the power law equation. Oat β-glucan from steamed samples were more viscoelastic than β-glucan from roasted or raw oat samples. Because viscous properties of β-glucan from boiling water extracts are influencedhydrothermal treatments without affecting polymer molecular weight, polymer interaction with the solvent must be affected. Steaming may disrupt intramolecular cross-linkings in native β-glucan, allowing a linear chain configuration to generate greater viscosity.