RHEOLOGICAL PROPERTIES OF (1-]3),(1-]4)-BETA-D-GLUCANS FROM RAW, ROASTED, AND STEAMED OAT GREATS

Effects of hydrothermal treatments (steaming, roasting) of oat grain o n beta-glucan extractability and rheological properties were tested on oat cultivars with low (Robert) and high (Marion) beta-glucan content . Steaming of grain reduced the amount of beta-glucan that could be ex tracted, compared with raw or roasted grain, but the extracts from ste amed grain had much greater viscosity. Increased extraction temperatur es increased the amount and the average relative molecular mass (M-r) value of beta-glucans extracted. In boiling water extractions, the ave rage M-r values among raw, roasted and steamed oat samples were equiva lent, but extracts from steamed oat grain had significantly higher int rinsic viscosity than the extracts from roasted or raw oat grains. bet a-Glucan solutions purified from steamed grain extracts were very visc ous and highly pseudoplastic, as described by the power law equation. Oat beta-glucans from steamed samples were more viscoelastic than beta -glucans from roasted or raw oat samples. Because viscous properties o f beta-glucans from boiling water extracts are influenced by hydrother mal treatments without affecting polymer molecular weight, polymer int eraction with the solvent must be affected. Steaming may disrupt intra molecular cross-linkings in native beta-glucan, allowing a linear chai n configuration to generate greater viscosity.