FRACTIONATION OF OAT (1-]3),(1-]4)-BETA-D-GLUCANS AND CHARACTERIZATION OF THE FRACTIONS

A commercial sample of oat beta-glucan was fractionated through stepwi se precipitation with ammonium sulphate to yield four fractions. These were analysed for apparent viscosity values, relative molecular weigh ts 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 exhibit ing lower molecular size and decreased limiting viscosity values were precipitated at higher concentrations of ammonium sulphate. Methylatio n analysis indicated that in all fractions beta-(1-->3) and beta-(1--> 4) linkages represented more than 90% of all linkages present. The bet a-(1-->3) to beta-(1-->4) ratio in the ii-actions decreased with molec ular size. beta-glucan fractions with distinct physical and structural characteristics were obtained with the ammonium sulphate fractional p recipitation technique. (C) 1998 Academic Press Limited.