Abstract:
Twenty nine samples of authentic A.nilotica var. tomentosa gum were collected from Sinnar and Blue Nile states of Sudan. Representative composite sample were prepared from all collected samples.
Physicochemical methods were undertaken to characterize the gum from Sinnar and Blue Nile states of Sudan. Results obtained for all parameters show insignificant differences within samples collected from different locations.
Mean values obtained for the studied properties were: moisture content 12.6%; and 11.95%; ash content 2.17%; and 1.94%; pH value 5.25; and 5.13; specific optical rotation +97.67; and+91.8, calorific value 4.04 Kcal mol-1; and 4.03 Kcal mol-1, intrinsic viscosity 10.16 cm3g-1; and 11.47 cm3g-1 , nitrogen content 0.08%; and 0.05%, protein content 0.51%; and 0.28%, acid equivalent weight 2182.87; and 2187.73, total uronic acid 8.90% ;and 8.88%, respectively. The relationship between tannin content and Colour Gardner were also studied for all samples. Studied cationic composition showed that calcium has the highest value among the studied cations, followed by potassium, iron and strontium.
Rheological study of A.nilotica var. tomentosa gum showed identical behaviour compared to A.nilotica var. nilotica gum, The flow behaviour is shear thinning under low shear rate and behaves as a Newtonian fluid at high shear rate and high concentrations. The results of oscillatory test of gum solutions revealed a typical liquid-like behaviour.
Molecular weight distribution was determined using gel permeation chromatography. The chromatogram showed three main components designated as arabinogalactan protein (AGP), arabinogalactan (AG) and glycoprotein (GP). Average molecular weight of the samples was estimated from light scattering measurement using GPC-MALLS technique. The values of Mw, was found to be 5.3x106 Da. for each. The radius of gyration was found to has an average of 43.5 nm.
Emulsification studies of A.nilotica var. tomentosa gum showed that the gum has the same emulsifying stability compared to A.nilotica var. nilotica, and has a very good emulsifying stability compared to A. senegal var. senegal
