Physicochemical, functional and microbial properties of crude and processed gum arabic (Acacia senegal)

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Kheir, Mahasin Elamin Mohammed
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Eight gum arabic formulations, namely; hand picked selected, cleaned, sifting, kibbled 105, kibbled 107, kibbled 119, kibbled 121 and spray dried were subjected for physicochemical, functional and microbial analysis in an attempt to set standard specifications for each. The formulations considered varied between raw and processed gum arabic of Acacia senegal to find out the influence of processing on properties of gum arabic. The analysis included certain parameters like; shape, color, mesh, solubility, moisture content, specific optical rotation, relative viscosity, intrinsic viscosity, acid insoluble ash, pH, ash, nitrogen, protein, reducing sugars, tannin, uronic acid, apparent equivalent weight, molecular weight, water holding capacity, emulsifying stability, bacterial count, yeasts count, moulds count and salmonella count. Water solubility showed some variations among the different gum formulations, with the highest for the spray dried (98.80%) and the lowest for the sifting formulation (97.40%). However the solubility in organic solvents (ethanol, acetone and chloroform) was generally very low yet with variations among the different formulations. The moisture content ranged between 9.90% for the hand picked selected and 8.32% for the spray dried. The specific optical rotation for the spray dried gum was -31.63=616;, whereas the raw hand picked selected gave -31.28=616; and the sifting -24.50=616;. The relative viscosity was almost similar for the eight formulations as 1.44 ml/gm for the spray dried, whereas the intrinsic viscosity showed differences among the eight gum arabic formulations(GAF), with the highest for the kibbled 105 (18.85) and the lowest for the kibbled 119 (11.49). The acid insoluble ash was lowest in spray dried (0.07%) and highest in sifting formulation (0.37%), for the pH the overall average was 4.22. The ash content ranged between 3.91% for the kibbled 121 and 3.05 for the spray dried. The nitrogen ranged between 0.42% for the hand picked selected and 0.37% for the spray dried. However, for reducing sugars, uronic acid and apparent equivalent weight, no significant differences were recorded between GAF and the values were 1.07%, 13.53%, and 1439.25 as an average respectively. The maximum water holding capacity was recorded for the spray dried (69.51%) and the least was in kibbled 105 formulations (66.43%). The maximum level in emulsifying stability was recorded for kibbled 107 and spray dried formulations as 1.03. Bacterial counts in cfu/gm (microbial load), ranged between 1.73=620;104 for hand picked selected and 1.33=620;102 for kibbled 119, no bacterial count was detected in the spray dried formulation. Less than 10 cfu/gm counts were detected for Moulds in all formulations. Further more the spray dried was found to be free of mould. No yeast and salmonella were detected in all formulations. The comparative studies indicated that, about 96% of the values of the parameters and factors studied in the GAF were consistent with the prescribed standards and specifications for gum arabic.
July 2005
(Acacia senegal)