Preliminary study of the gelling properties of polysaccharide isolated from the fruit of Cordia abyssinica.

Cordia abyssinica is a small tree that grows in riverine bush in Southern Africa. The gum, extracted from the fruit of C. abyssinica, by precipitation with ethanol from solutions that contained 0.25 M NaCl, gelled when suspended in water at concentrations higher than 0.15%. Optimum gel formation occurred at neutral pH and 4 degreesC when solutions were left overnight. Addition of sucrose or monovalent ions at concentrations up to 10% and 50 mM respectively had no effect on gel formation. Addition of calcium ions or EDTA resulted in poorly formed gels. At concentrations of calcium ions above 20 mM, no gels were formed. The firmness of the gels depended on whether the gum had been ground into a powder or not with unground material producing firmer gets. Upon heating plain gels or those prepared in the presence of sucrose, the gels melted into viscous masses. On cooling, the melted gels formed lumpy masses with proper gels not reforming.