Heterogeneity in a water-extractable rye arabinoxylan with a low degree ofdisubstitution

From rye grain samples, water extractable arabinoxylan with a low degree of disubstitution (AX I) was isolated by fractionation on a DEAE-cellulose co lumn. AX I of all rye samples had a similar relative composition of un- and monosubstituted xylose residues and with less than 5% disubstitution. It s howed a shear thinning behaviour and the viscosity was related to molecular weight. AX I isolated from different rye varieties had different viscositi es at the same concentration. One rye sample had a weight average molecular weight of 125 000 (polydispersity 2) according to calculations from both l ight scattering and viscosity data. Signals from un- and monosubstituted xy lose residues in C-13 NMR spectra were assigned using C-13-HSQC-DEPT and CO SY techniques. AX I probably consisted of blocks or different molecules wit h sparsely and more densely substituted regions. (C) 2000 Elsevier Science Ltd. All rights reserved.