The characterization of Acacia paolii gum and four commercial Acacia gums from Kenya

Abstract

Water-soluble gums from Kenya are reputed to be variable in quality and to differ in functional properties from Sudanese gum arabic, but analytical data for Kenyan gums, capable of explaining such observations, have not been available. The gum from Acacia paolii Chiov., a tree of unusual appearance and widespread occurrence in Kenya, has been shown to be dextrorotatory but analytically different from gum talha ( A.seyal). Of four other Kenyan samples studied, gum from the Lemote district is also dextrorotatory; in contrast, gum samples from Haut, Marsabit and Nyoke are laevorotatory but easily distinguishable analytically from classical gum arabic ( A.senegal) in terms of their specific rotations; viscosities; nitrogen, methoxyl and rhamnose contents; and galactose/ arabinose ratios. These analytical differences are reflected in the different efficiencies of these gums as emulsifiers. Fourier-transform 13C-NMR spectra confirm that the gum from A.paolii (+90°) differs from Sudanese gum talha ( A.seyal, +56°) and that gum arabic ( A.senegal, −30°) differs structurally from the gum from Marsabit. Although measurement of specific rotation distinguishes between gum arabic and gum talha, this simple test is not sufficient to establish that a sample of gum arabic originates solely from A.senegal and is therefore likely to have the unique functional properties of that gum essential for manufacturing purposes; for such an assurance, other analytical parameters must also conform to the values established for A.senegal gum.