The emulsification properties of octenyl- and dodecenyl- succinylated inulins

Abstract

The emulsification properties of a series of inulin samples modified using varying amounts of octenyl- and dodecenyl-succinic anhydride have been studied by determining the droplet size as a function of time, temperature and in the presence of electrolyte using laser diffraction. It was found that ∼2% modified inulin was required to stabilise 15% w/v medium chain triglyceride emulsions and that the minimum droplet size was achieved when the % hydrophobe content was >8 mol%. The dodecenyl derivatives produced emulsions with a smaller droplet size than the octenyl derivatives. Apart from OSA-inulin with a low degree of modification, stability was maintained when stored for a period of up to 21 days at room temperature and at 50 °C. The zeta potential of the emulsion droplets was determined by Laser Doppler Velocimetry and was found to increase from ∼5 mv to ∼60 mv as the pH increased from 2 to 7 due to the presence of carboxylate ions present in the linkage between the inulin and alkenyl chains. The droplet size was found to increase on the addition of electrolyte indicating that the adsorbed polymer layer was insufficient to provide a steric repulsive barrier and that stabilisation was mainly due to electrostatic repulsive forces.