AN EVALUATION OF METHODS FOR CHARACTERIZING AND MONITORING GUM-ARABICOF COMMERCE AND RELATED ACACIA GUMS

Three methods that have been suggested as inexpensive for characterisa tion of gum arabic were evaluated in characterising and monitoring gum arabic of commerce, The methods were; physico-chemical and carbohydra te analysis (analytical), determination of molecular mass by gel perme ation chromatography (gpc) and an Enzyme Linked Immunosorbent Assay (E LISA). The results revealed that gpc provides quick and consistent inf ormation on gum arabic of commerce from Acacia senegal. It was able to detect the three chemical species; Arabinogalactan protein complex (A GP), Arabinogalactan (AG) and Glycoprotein (GP) fractions that are typ ical of A. senegal and could differentiate gum from the two varieties of A. senegal, i.e., var. senegal and var. kerensis on the basis of th e enhanced UV peaks in the later. It was able to distinguish gums from different Acacia species as well as suspected contaminants. The analy tical method could differentiate between the two varieties of A. seneg al on the basis of optical rotation, protein content and viscosity whi ch were noted as basic parameters for comparison. However, where the p roposed FAO (1990) specifiction was applied in its present form, it fa iled to adequately characterise gum from var. kerensis as gum arabic. Secondly, natural product variability i.e., the observed between sampl e variation made the method to have limited application in adequately characterising gum arabic from even a single source. The method was ab le to distinguish gums from the other Acacia species purely on the bas is of optical rotation though information on nitrogen and sugar compos ition was also invaluable. Generating data on the composition of sugar s requires time that militates against the method as a slow process. B ecause of the overlap in the analytical parameters for some samples, i t could be adequately characterise two of the samples that were presen ted as suspected contaminants. Nonetheless, by combining information o f gpc and analytical data, a better evaluation of the gums was achieve d. The method of Elisa has a future scope but will require refining it by utilising monoclonal antibodies to be developed for it to be more specifc in characterising gum arabic from A. senegal.