Development and stability of microemulsions as carriers for nutraceuticals

The formulation and chacterisation of food-grade water-in-oil (s/o) microemulsions as carriers for bioactive molecules are studied. The microemulsions consisted of deionised water, polysorbate 80, soybean oil, glycerol monooleate and sodium chloride (as a model marker). The formulated microemulsions were studied for droplet size via dynamic light scattering and transmission electron microscopy, conductance and viscosity. Phase bahaviour was studied along two dilution lines. Along these dilution lines, microemulsions were loaded with NaCl at their maximum solubilisation capacity. The stability of the microemulsions with and without NaCl was studied visually and through droplet size determination. Using a conductivity meter, sodium chloride-containing microemulsions were studied for release along one of the dilution lines. The release mechanism was established based on visual observation and using confocal laser scanning microscopy. The release of sodium chloride upon de-stabilisation of the microemulsion resulted from phase inversion. This phase inversion was brought about by the dilution of the microemulsion upon ingress of water as a result of osmosis. Overall, this study demonstrated that microemulsions have the potential to solubilise hydrophilic food additives such as NaCl and the solubilised additive (sodium chloride) could be released following microemulsion de-stabilisation.