An investigation on the stability of the hazelnut oil-water emulsion

In this study, the stability of the emulsion of two immiscible liquids, including the effect of surfactants and agitation systems has been evaluated. The working fluid was hazelnut oil in water. Three different surfactants-two anionic sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS) and a nonionic (Tween-20) - were tested. To assess the effect of surfactant type and agitation speed on droplet size distribution, focused beam reflectance measurement (FBRM) was employed. Emulsions prepared with both surfactant types, that is, anionic and nonionic, were better stabilized than emulsions with no surfactant. Droplet size decreased when the surfactant concentration was increased, until critical micelle concentration (CMC) of surfactants was reached. Once the CMC was reached, the variation in droplet size was significantly reduced or eliminated with any further increase in its concentration. The interfacial tension (IFT) was found to be a function of surfactant concentrations: with an increase in the surfactant concentration, the adsorption of surfactant molecules increased at the oil-water interface. The IFT remained unchanged when the micelles formed in the aqueous phase above CMC. Data analysis from FBRM revealed that higher agitation speed produced finer droplets. The destabilization time scale of emulsions in the presence of different surfactants was also assessed using electrical resistance tomography (ERT).