Structural features of water-soluble arabinogalactans from Norway spruce and Scots pine heartwood S. Willfo ¨r, R. Sjo ¨holm, C. Laine, B. Holmbom Abstract Isolated water-soluble acidic arabinogalactans from Norway spruce and Scots pine heartwood were analysed and compared to Siberian larch heartwood arabinogalactans. The carbohydrate monomer composition was determined by acid methanolysis and gas chromatography, while structural studies were performed by 13 C NMR spectroscopy and methylation analysis. The main structural features were found to be the same in the three types of arabinogalactans. However, the structure of the arabinogalactans from spruce and pine were found slightly different from the structure of larch arabinogalactans. The amount of single unit side-chains, consisting of arabinose and glucuronic acid units, was higher in the spruce and pine arabinogalactans than in the larch arabinogalactans. The amount of glucuronic acid was higher in the spruce arabinogalactans than in the pine arabinogalactans. The pine arabinogalactans had a higher amount of side chains with more than two sugar units than the spruce arabinogalactans. Introduction Water-soluble polysaccharides are released and accumulated into process waters in the production of mechanical pulp and wood-containing paper. Especially detrimental in papermaking are anionic polysaccharides, so-called ‘‘anionic trash’’, which can form complexes with various cationic polymers used by the Originals Wood Science and Technology 36 (2002) 101–110 Ó Springer-Verlag 2002 DOI 10.1007/s00226-001-0137-x Received 30 December 1999 Stefan Willfo ¨r (&), Bjarne Holmbom A ˚ bo Akademi University, Process Chemistry Group, c/o Laboratory of Forest Products Chemistry, Porthansgatan 3, 20500 Turku/A ˚ bo, Finland e-mail: stefan.willfor@abo.fi Rainer Sjo ¨holm A ˚ bo Akademi University, Laboratory of Organic Chemistry, Biskopsgatan 8, 20500 Turku/A ˚ bo, Finland Christiane Laine The Finnish Pulp and Paper Research Institute KCL, P.O. Box 70, 02151 Espoo, Finland This work is part of the activities of the A ˚ bo Akademi Process Chemistry Group, a National Centre of Excellence supported by the Academy of Finland. The work performed at KCL was partly financed by the Technology Development Centre of Finland (TEKES). 101 © 2002 Springer-Verlag. Reprinted with permission from Wood Science and Technology 36, number 2, pages 101-110.