Synthesis of cationic alkylated chitosans and an investigation of their rheological properties and interaction with anionic surfactant.

Two methods were used to alkylate high MW chitosan with glycidyltrimethylammonium chloride (GTAC) in order to produce chitosan derivatives that are water-soluble throughout the pH range. In addition, a novel chitosan derivative was created by alkylating one of the products with the GTAC analogue Quab 342 containing C12 alkyl chains. The phase behaviour and rheological characteristics of the chitosan derivatives were studied in the presence of anionic surfactant. The derivatives were found to form soluble complexes at low and high SDS concentrations and that the Quab 342 derivative was able to form gels.

The interfacial, emulsification and encapsulation properties of hydrophobically modified inulin.

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.

Synthesis, characterisation and physicochemical properties of hydrophobically modified inulin using long-chain fatty acyl chlorides.

A series of inulin derivatives were synthesized in aqueous solution using acyl chlorides with varying alkyl chain length (C10-C16). They were characterised using a number of techniques including MALDI TOF-MS, 1H NMR and FTIR and their degree of substitution determined. The solution properties of the hydrophobically modified inulins were investigated using dye solubilisation and surface tension and it was confirmed that the molecules aggregated in solution above a critical concentration (critical aggregation concentration, CAC). The value of the CAC was found to be reasonably consistent between the different techniques and was shown to decrease with increasing hydrophobe chain length. It was found that the C10, C12 and C14 derivatives formed stable oil-in-water emulsions and the emulsion droplet size decreased with increasing alkyl chain length. The C16 derivative was not able to produce stable oil-in-water emulsions; however, it was able to form stable water-in-oil emulsions. The fact that the derivatives are able to form micellar-like aggregates and stabilise emulsions makes them suitable candidates for the encapsulation and delivery of active compounds with potential application in food, cosmetic, personal care and pharmaceutical formulations.

Synthesis, characterization and self-assembly of biosurfactants based on hydrophobically modified inulins.

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.

Control of the properties of xanthan/glucomannan mixed gels by varying xanthan fine structure.

The interaction of native xanthan gum, deacetylated xanthan gum and depyruvated xanthan gum with konjac glucomannan has been studied using DSC and controlled stress rheometry. In the absence of electrolyte the DSC cooling curves for native xanthan and deacetylated xanthan showed a single peak and there was a corresponding sharp increase in the storage modulus indicating gel formation. It is apparent that on cooling, association of the konjac glucomannan with the native xanthan molecules is triggered by the xanthan coil-helix transition. In the presence of electrolyte, there were two DSC peaks observed. The higher temperature DSC peak was attributed to the xanthan coil-helix transition while the lower temperature DSC peak was attributed to konjac glucomannan-xanthan association as noted by an increase in the storage modulus. The gels formed were much weaker than those in the absence of electrolyte. The DSC cooling curves for depyruvated xanthan in the absence of electrolyte showed two peaks. The higher temperature peak was attributed to the coil-helix transition while the lower temperature peak corresponded to gelation as noted by an increase in the storage modulus. The gels were very much weaker than for native xanthan gum and deacetylated xanthan gum.

Considering the needs of carers: a survey of their views on services.

This paper describes a survey undertaken in Derbyshire. A total of 244 carers responded to a postal questionnaire enquiring about the services they needed, how they rated the services used, how they coped generally, and whether they would need long-term day, respite or residential care. The responses suggested that carers were keen to express their views. Most wanted advice on benefits, and satisfactorily rated the services they received. Those who found it hardest to cope were caring for elderly parents or children, and had other family or work commitments. The authors conclude with a plea for consultative research to play an integral role in service planning and evaluation.