Characterization and Study of Functional Properties of Acacia nilotica var. adstringens GUM

Abstract

The objective of this study was to investigate parameters in Acacia nilotica var. adstringens gum, which is available in Sudan. In total there were 45 samples of authentic Acacia nilotica var. adstringens gum were collected from North Kordofan state west of Sudan during season 2016-2017. Physicochemical methods were undertaken to characterize the gum and to study its functional properties. Parameters such as moisture and ash contents, pH, specific optical rotation, intrinsic viscosity, nitrogen and protein content, acid equivalent weight, total uronic acid, tannin content and calorific value were determined. The results show that the mean of moisture and ash content 11.01% and 2.06%, pH 5.06, specific optical rotation +96.4, intrinsic viscosity 11.06 cm3g-1, nitrogen content 0.06%, protein content 0.44%, acid equivalent weight 1869, total uronic acid 10.40% , tannin content 0.04% and calorific value 4.064 Kcal/g. Acid hydrolysis of Acacia nilotica var. adstringens gum followed by (HPLC) measurements revealed that sugar content is arabinose 52%, galactose 24% and traces of rhamnose (< 1). Cationic composition showed that calcium has the highest value among the cations studied (3x10-1 %), followed by magnesium (5x10-2 %), potassium, (4.5x10-2 %), sodium (4x10-2 %), iron (5.8x10-3% ), strontium (4 x10-3% ), manganese (3x10-3 %), tin (2.4x10-3% ) , zinc (2x10-3 %), copper (5.4x10-4% ) and nickel (9x10-5 %) respectively. Molecular weight distribution was determined by fractionation of the gum using gel permeation chromatography. The results showed t hat three main components designated arabinogalactan protein (AGP), arabinogalactan (AG) and glycoprotein (GP) were resolved. The molecular weight of the sample was estimated from light scattering measurement using GPC-MALLS technique. The value of Mw was found to be 2.54x106 Da. The radius of gyration was found to have an average of 36.6 nm. Emulsification studies of Acacia nilotica var. adstringens gum showed that the gum has the same emulsifying stability compared to A. nilotica var. nilotica and A. nilotica var. tomentosa. Rheological study of Acacia nilotica var. adstringens gum show that the flow behaviour is shear thinning under low shear rate and behave as a Newtonian fluid at high shear rate. The results of oscillatory test of gum solutions revealed a typical liquid-like behaviour.