Physicochemical characterisation of the galactomannan from Delonix regia seed

This paper reports on the physicochemical characteristics of the polysaccharide extracted from the seed of the legume Delonix regia which grows abundantly in Nigeria. The polysaccharide was found to consist of mannose and galactose with an M:G ratio 5:1 and average molar mass of 7.23 × 105 g/mol. The average value of intrinsic viscosity obtained using Fedors, Huggins and Kraemer equations was 9.9 dL/g. The double logarithmic plot of zero shear specific viscosity versus volume concentration gave a critical overlap concentration of 0.404 g/dL with a slope of 1.2 below and 6.8 above the critical overlap concentration. Under oscillatory shear, at polysaccharide concentrations less than 1% solutions exhibited purely viscous properties while at higher concentrations they exhibited the properties of a weak gel. The physicochemical characteristics of the polysaccharide were found to be similar to locust bean gum and therefore it has potential as a thickener in the Food and related Industries.