Solution characteristics and thermorheology of Prosopis africana seed polysaccharide

Of about forty four species of the Prosopis family known, only Prosopis africana is indigenous to Africa. We have isolated the polysaccharide constituent of P.rosopisafricana seed and studied its solution properties. The polysaccharide had a weight-average molecular weight of 1.72 × 106 g/mol and intrinsic viscosity of 11.6 dL/g. The effect of concentration and temperature on the polysaccharide viscosity and microstructure were investigated under steady and dynamic shear. The polysaccharide showed typical shear thinning characteristics and the critical angular frequency at the G-crossover points (G′ = G″) was concentration and temperature dependent and shifted to lower frequencies at higher polysaccharide concentrations. The onset of polymer overlap occurred at a critical concentration, c* = 0.186 g/dL with slope of 1.4 below and 4.4 above the point of polymer overlap concentration. The rheological behavior was studied as a function of temperature and the activation energy for viscous flow of 2% solution of the polysaccharide was calculated to be 24.3 kJ/mol. The rheological properties were shown to be similar to guar gum and hence it has potential use as a thickener in foods