COMPOSITION AND PHYSICOCHEMICAL PROPERTIES OF LINSEED (LINUM-USITATISSIMUM L) MUCILAGE

Linseed (Linum usitatissimum L.) mucilage, consisting mainly of water-soluble polysaccharides, was isolated from the seeds and a partially defatted meal by different extraction regimes. The mucilage yield (3.6-9.4%) and level of contaminating proteins varied substantially with the temperature of extraction and nature of the raw material; lower yields of relatively pure polysaccharide extracts were obtained from the seeds at 4 degrees C. Although the relative monosaccharide composition varied with the extraction conditions, galacturonic acid, galactose, xylose, and rhamnose were the major monosaccharides; fucose arabinose, and glucose were minor constituents. Purified mucilage was further fractionated into mainly neutral and acidic polysaccharides by selective precipitation with cetyltrimethylammonium bromide (it complexes preferentially with polysaccharides of high charge density), as revealed by galacturonic acid analysis and C-13 NMR. The neutral polysaccharide fraction, having a higher intrinsic viscosity ([eta] = 6.6 vs 4.6 dL/g), exhibited more pronounced shear thinning and viscoelastic responses in solution than its acidic counterpart. All mucilage preparations exhibited stable viscosity in the pH range 5.0-9.0; however, large reductions in viscosity were seen with the addition of electrolytes. The water binding capacity (1600-3000 g of H2O/100 g of solids) and theological properties of mucilage resembled those of guar gum.