CHEMICAL-STRUCTURE, MOLECULAR-SIZE DISTRIBUTIONS, AND RHEOLOGICAL PROPERTIES OF FLAXSEED GUM

Flaxseed gum extracted under optimum conditions of temperature (85-90 degrees C), pH (6.5-7.0), and a water:seed ratio (13.0) was subjected to dialysis and fractionation by ion exchange chromatography on a high-capacity DEAE-cellulose column. The two fractions obtained [an acidic fraction (AFG) and a neutral fraction (NFG)] were characterized on the basis of molecular size distributions, chemical structure, and theological properties. The neutral fraction was composed of arabinoxylans and was free of uronic acids. The acidic fraction consisted mainly of pectic-like polysaccharides containing L-rhamnose, D-galactose, and D-galacturonic acid. The higher viscosity of solutions of the neutral fraction can be explained by the presence of a beta-D-(1,4)-xylan backbone of the arabinoxylan component, exhibiting a higher hydrodynamic volume than the acidic fraction. In contrast, the weak solution theological properties of the acidic fraction could be attributed to the smaller molecular size of its constituent polysaccharides.