Biosurfactants have been synthesized using a low energy, environmentally friendly process by the derivatization of inulin with octenyl (OSA) and dodecenyl (DDSA) succinic anhydrides in aqueous solution. The inulin and its derivatives have been characterized using gel permeation chromatography/multi angle light scattering (GPC/MALLS), high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), Fourier transform infrared spectroscopy (FTIR), and NMR, and the reaction efficiency was found to be between 59 and 95%. The efficiency was generally higher for OSA derivatives compared to DDSA derivatives. The hydrophobic derivatives were found to aggregate in solution and the critical aggregation concentration (CAC) was determined using dye solubilization, surface tension, dynamic light scattering (DLS), and conductivity. There was reasonable agreement in the CAC values obtained by the different techniques except for conductivity. It was found that the CAC decreased with increasing alkenyl chain length and degree of modification, and the values were significantly lower for the DDSA derivatives compared to the OSA derivatives. GPC elution profiles for the DDSA-inulin using 12 mol % reagent confirmed the presence of aggregates with a molecular mass of ∼2.5 × 10(6) g/mol and a radius of gyration of ∼25 nm corresponding to ∼550 inulin molecules. DLS study was undertaken to determine the hydrodynamic radius, and values obtained for the DDSA (12%) derivative were 30 nm in both water and 0.1 M sodium nitrate, while for the OSA (12%) derivative values of 13 and 7 nm were obtained. The derivatives have potential application in the stabilization of particulate dispersions and emulsions and also in the encapsulation and delivery of drugs.

Octenyl- and dodecenyl succinic anhydride derivatives (OSA- and DDSA-) of inulin have been synthesised and their solution and interfacial properties have been determined and compared to a commercially available alkylated inulin, Inutec SP1. All samples formed micellar aggregates in solution above a critical concentration (critical aggregation concentration) and were able to 'dissolve' a hydrophobic dye. They were also able to form stable oil-in-water (O/W) emulsions as assessed by measurements of their droplet size as a function of time. DDSA-inulin with a high degree of substitution was found to be effective at encapsulating beta carotene using the solvent evaporation method which yielded a solid which dissolved readily in simulated gastric fluid. The results confirm the potential application of these materials in a number of areas including, drug delivery, pharmaceuticals, neutraceuticals, cosmetics and personal care.

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a b s t r a c tThe emulsification properties of a series of inulin samples modified using varying amounts of octenyland 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 OSAinulin 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.

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