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 d efatted meal by different extraction regimes. The mucilage yield (3.6- 9.4%) and level of contaminating proteins varied substantially with th e temperature of extraction and nature of the raw material; lower yiel ds of relatively pure polysaccharide extracts were obtained from the s eeds at 4 degrees C. Although the relative monosaccharide composition varied with the extraction conditions, galacturonic acid, galactose, x ylose, and rhamnose were the major monosaccharides; fucose arabinose, and glucose were minor constituents. Purified mucilage was further fra ctionated into mainly neutral and acidic polysaccharides by selective precipitation with cetyltrimethylammonium bromide (it complexes prefer entially with polysaccharides of high charge density), as revealed by galacturonic acid analysis and C-13 NMR. The neutral polysaccharide fr action, having a higher intrinsic viscosity ([eta] = 6.6 vs 4.6 dL/g), exhibited more pronounced shear thinning and viscoelastic responses i n solution than its acidic counterpart. All mucilage preparations exhi bited stable viscosity in the pH range 5.0-9.0; however, large reducti ons in viscosity were seen with the addition of electrolytes. The wate r binding capacity (1600-3000 g of H2O/100 g of solids) and theologica l properties of mucilage resembled those of guar gum.