Distribution and some properties of cell wall polysaccharides in rye milling fractions

A rye sample (cv. Voima) was fractionated by a laboratory scale roller mill into eight fractions: six flour fractions and bran and short fractions originating from the outer kernel layers. The extractabilities of dietary fibre and pentosan were clearly higher in the flour fractions than in the outer fractions. Pentosan and beta-glucan were present throughout the kernel indifferent proportions, although in much higher amounts in the outer parts. The pentosan present in the outer layers was less branched (arabinose:xylose 0.63-0.75) than that in the flour fractions (arabinose:xylose 1.1-1.2). The outer fractions showed the highest water absorption capacities. When extracted with water the fractions yielded solutions with different viscosities, and the shorts extract had clearly the highest viscosity. Extract viscosity was shown to correlate with the content of water-extractable pentosan in the particular fraction. The molecular mass of the solubilised pentosans varied from 150 000 to 800 000 as revealed by size exclusion-HPLC with laser light-scattering detection. The pentosan with lower molecular mass was shown to be less branched than the larger polymers. (C) 1997 Academic Press Limited.