Synthesis, characterization and emulsification properties of dodecenyl succinic anhydride derivatives of gum Arabic

Gum Arabic, GA, has been chemically modified using dodecenyl succinic anhydride (DDSA) in aqueous solution and the products have been characterized and their solution and emulsification properties evaluated. FTIR was used to confirm that derivatisation had occurred and the hydrophobe incorporation and reaction efficiency was determined by a simple titration method. The derivatives, DGA5 and DGA10 were found to contain 5 and 10 %w/w DDSA respectively. Surface tension and dye solubilisation measurements demonstrated that the modified GA samples aggregated in solution at a specific concentration, referred to as the critical aggregation concentration, CAC. The value of the CAC was found to be a function of the degree of substitution and values of 0.1% and 0.04% were obtained for DGA5 and DGA10 respectively. The emulsification properties of the polymers were assessed by determination of the droplet size as a function of polymer concentration and time using laser diffraction. The droplet size decreased for all samples as the polymer concentration increased but the minimum droplet size obtained increased in the order DGA10 < DGA5 < GA indicating enhanced emulsification efficiency with increasing hydrophobe content. The effect of ageing on emulsion stability was assessed and the droplet size of emulsions prepared with GA and DGA5 increased with time but remained constant for samples prepared with DGA10. Emulsion creaming was followed using the Turbiscan and it was noted that DGA5 and DGA10 were much more effective than GA at reducing creaming. The results have demonstrated that the modified gum Arabic samples have potential application for microencapsulation.