Processing optimization and physico-chemical characteristics of flaxseed polysaccharide gums

Abstract Response surface methodology was used to optimize the aqueous extraction of polysaccharides from flaxseed. Temperature, pH and seed/water ratio were the major parameters affecting yield, chemical composition and rheological characteristics of the crude gum extract. Optimum conditions for extraction were a temperature of 85-90°C and a neutral pH (6.5-7). Seed/water ratio had a smaller effect on yield and properties of flaxseed gum than temperature and pH. Flaxseed gum extracted under optimum conditions gave relatively high yield (7.9%) and contained over 80% carbohydrates. Using ion exchange chromatography, on a DEAEcellulose column, the crude flaxseed gum was dialyzed and further separated into a neutral and an acidic fraction. Protein content, minerals, monosaccharide composition and uronic acid levels of flaxseed gum fractions were determined. Further structural information and molecular size distributions of the gum and its fractions were obtained by methylation analysis, 13C NMR and gel filtration chromatography. Flaxseed polysaccarides exhibited shear thinning and weak gel properties at concentrations above 1% (w/w). The neutral flaxseed gum fraction (NFG) was of higher molecular size and showed similar shear thinning behavior as the crude and dialyzed gums. The acidic fraction, on the other hand, consisted of low molecular size polymers and exhibited Newtonian-like flow behavior.