Extraction, characterization and rheological study of the purified polysaccharide from Lallemantia ibrica seeds.

Polysaccharides are broadly used as plasticizing, emulsifying, stabilizing, thickening, gelling, binding and coating agents. The optimum extraction point based on highest yield and total carbohydrate content and lowest amount of protein was extraction temperature of 68.75 °C, pH = 10 and water to seed ratio of 36:1. Lallemantia ibrica seed gum (LISG) is a high molecular weight polysaccharide (5.74 × 106 g/mol) containing, on average, 89.60% carbohydrate, 2.98% protein, 8.95% ash, 0.2% fat and 6.52% moisture. FTIR and 1H NMR analysis revealed the presence of galactose, mannose, rhamnose, uronic acid and O-acetyl functional groups. The intrinsic viscosity of LISG (at 25 °C) was estimated to be 1.96 dL/g. The gum solutions had a shear-thinning behavior at all tested concentrations, and the Power-law model satisfactory described their rheological behavior. It was found that deionized water (pH = 7 at 25 °C) is a good solvent for LISG macromolecules. The shear thinning behavior of LISG and its high viscosity at low concentration make it a good stabilizer and thickener in the food industry.