Global versus local dynamics during destabilization of eco-friendly cosmetic emulsions

Eco-friendly cosmetic emulsions are usually less stable than conventional ones as they involve milder chemicals or less intense (energy consuming) production processes. In order to improve their stability it is important to understand local phenomena occurring within the emulsions during phases separation. Most of the techniques for monitoring local emulsion stability provide information of droplet sizes either from direct visual observations at the boundaries of the emulsion (container wall) or from measurements on withdrawn samples. Therefore, non-intrusive, continuous techniques, capable of sensing the destabilization of emulsion over the entire cross-section of a container, are of particular significance. In this context, measurements of a dual-probe local electrical conductance technique are compared with global volumetric measurements. Eco-friendly cosmetic oil-in-water emulsions are produced with different olive oil fractions, emulsifier (GMS) concentrations and agitation schemes. Local information from electrical signals indicated flocculation phenomena which were completely missed by global volumetric measurements.