Characterization and Thermodynamic Studies of Acacia Nilotica Gum of Sudanese Origin

Abstract

A number of physicochemical properties (moisture, ash, pH, nitrogen and protein content, specific rotation, intrinsic viscosity) and total sugars content were used to characterize Acacia nilotica gum of Sudanese origin. The general characteristic of A. nilotica gum and the mean values of all properties studied are as follows : moisture content 9.3%, ash content 1.7 %, nitrogen 0.1%, protein 0.6 %, specific rotation +107, intrinsic viscosity 8.117cm3g-1 and pH 5.05. Cationic composition of gum samples was also determined and results show that calcium has the highest value followed by magnesium, sodium, potassium, iron and zinc. Sugar composition was estimated using HPLC technique where galactose and arabinose content were found to be 15.5% and 81.9% respectively. Molecular weight of A. nilotica gum was determined using osmometric technique and was found to be 2.3*106 Dalton. Thermodynamic parameters including the density, the partial specific volume of A. nilotica gum and solvent (water) and the volume fraction were estimated and found to be 2.32 gcm-3 and 0.99 gcm-3, 0.0003cm3g and 0.0005 cm-3g, 0.625 and 0.375 respectively. Chemical potential range have been calculated from osmotic pressure measurement for different concentration of gum solutions and was found to be 1.16 erg g-1 . Second virial coefficient and free energy of mixing were found to be 0.64cm2.mole/g2 and 1.78 erg g-1 respectively.