Fractionation of oat (1→3), (1→4)-β-D-glucans and characterisation of the fractions

A commercial sample of oat beta-glucan was fractionated through stepwise precipitation with ammonium sulphate to yield four fractions. These were analysed for apparent viscosity values, relative molecular weights using high-performance size-exclusion chromatography, and Chemical structure by methyl methylation analysis and analysis of water-soluble fragments released from the fractions by lichenase. Fractions exhibiting lower molecular size and decreased limiting viscosity values were precipitated at higher concentrations of ammonium sulphate. Methylation analysis indicated that in all fractions beta-(1-->3) and beta-(1-->4) linkages represented more than 90% of all linkages present. The beta-(1-->3) to beta-(1-->4) ratio in the ii-actions decreased with molecular size. beta-glucan fractions with distinct physical and structural characteristics were obtained with the ammonium sulphate fractional precipitation technique. (C) 1998 Academic Press Limited.