Radiation-induced polymerization of gum arabic (Acacia senegal) in aqueous solution

In this study, the gum arabic was used as Acacia senegal. Chemical and physical changes induced by treatment with ionizing radiation were investigated, and doses up to 100 kGy were employed. In the solid state, no significant changes in physical properties of gum arabic could be observed, although there was a small decrease in molecular weight. In aqueous solution at low concentration, gum arabic was mainly degraded, but a small amount of polymerization could also be detected. However, in highly concentrated aqueous solutions, polymerization occurred with minimal degradation. This novel polymerization of gum arabic occurred without the need for any additives and only by using high solute concentrations. Such polymerized gum arabic could be useful as a component in food, cosmetic, agricultural, and hygienic materials. Irradiation at high solute concentrations would provide favourable conditions for the radiation-induced radicals to combine, and so produce step-wise the polymerized gum arabic. These reactive species could result from both direct radiation action and abstraction by water radiolysis products. Gum arabic in aqueous solution at low concentrations, on the other hand, would mainly lead to carbohydrate-free radicals as a result of OH-radical abstraction, which would degrade further, rather than have the opportunity to re-combine.