Characterization and physicochemical Study of Acacia gerrardii gum of Sudanese origin

Abstract

Thirty samples of acacia gerrardii gum were obtained as natural exudates, and collected after tapping from Khor Tamba, Barak Alla, Gardod Duleyba and Umshara around Lagawa Town(South kordofan State, Sudan,) in the seasons 2008/2009---2009/2010. The samples were analysed for determination of moisture content, ash content, nitrogen and protein content, total soluble fiber, pH, specific optical rotation, relative and absolute viscosity, specific and intrinsic viscosity, molecular weight, equivalent weight and total uronic acid content, mineral and sugar composition, and emulsion stability. The mean values for moisture and ash content were found to be 6.5% and 1.89%. The average values for nitrogen, protein, total soluble fiber and pH were found to be 2.7%, 18.9%, 73.3%, and 5.35 respectively. Specific optical rotation has an average value of +46.30. Absolute viscosity, relative viscosity, specific viscosity and intrinsic viscosity were determined for the gum samples using water as a solvent. Intrinsic viscosity was found to be 33, 21.7 and 67ml/g for Khor Tamba, Gardod Duleyba and Umshara( L1, L3 and L4) samples . The intrinsic viscosity for Barak Alla(L2) samples was found to be 224ml/g. he molecular weight of the samples were determined using osmotic pressure techniques, the mean of the number average molecular weight Mn-- was found to be 5.5x 106.The second virial coefficient was calculated from osmotic pressure measurements and was found to be 0.17. Equivalent weight and total uronic acid content were also determined and were found to be in the average of 1273 and 15.6 respectively. Mineral composition of four representative samples (one sample from each location) of the samples were studied using flame photometer for determination of Ca, Na and K and Atomic absorption spectroscopy(AAS) technique for determination of Mg, Pb, Cd, Cu, Zn and Ni. The study showed that Ca+2 had the higher value 55 ppm. followed by Cd and Pb (13.8,10.08 ppm) then, K, Mg,(7.25, 4.35 ppm), Na, Cu, Zn 0.8, 0.38,o.85 ppm and finally Ni as traces of 0.06ppm. Sugar composition was estimated using high performance liquid chromatography (HPLC) technique. The neutral sugars obtained were arabinose, galactose and rhmnose, their mean values were found to be 55.9mg/ml, 9.70 mg/ml and 0.46mg/ml respectively. Finally emulsion stability of four composite samples usingtwo oils(groundnut and sesame) was determined and was found to be ranged from 0.51 to 0.79 and 0.71 to 1.55 respectively.