The chemical composition and some physical properties of a water-soluble gum from Prosopis africana seeds

A water-soluble gum was extracted from the endocarp capsule of the seed coat of Prosopis africana. The gum yield varied substantially with the method of dehulling. Maximum yield was obtained after boiling in 0.1 m Na2CO3 for 4 h. The effects of two different gum concentrations on the rheological properties of gum solutions were examined. The gum formed viscous solutions at low concentrations and exhibited stable viscosity in the pH range 6.0–8.0. Chemical analyses showed that the purified gum had a composition of 2.4% fat, 1.04% protein, 21.5% crude fibre and a gelation concentration of at least 10%. Galactose and mannose were the major polysaccharides identified. Large reductions in viscosity were observed with the addition of various concentrations of Na+ salts. The activation energies of flow for 2 and 3% gum solutions were in the range of 19.2–22.8 kJ mol−1 and were characteristic of systems with little intra- and intermolecular interactions.