On the key role of process parameters to control stability and properties of Pickering emulsions stabilized by montmorillonite

Abstract

In many applications such as cosmetics, emulsions are largely developed thanks to organic surfactants which lower the interfacial oil/water tension thus enhancing dispersions stability. However, molecular organic surfactants may be toxic to the skin as well as cause environmental contamination issues. The objective of the present work is to develop emulsions stabilized by natural particles such as montmorillonite. In particular, the influences of the dispersion and emulsification times as well as the homogenization process (high shear mixer or ultrasonication) were investigated. Obtained emulsions were conditioned at 40 °C and their properties were studied over 72 h. Macroscopic observations of stability with regards to creaming, emulsion microstructure characterization by optical microscopy as well as droplet size measurements were performed. The emulsion microstructure has been shown to be highly sensitive to the manufacturing parameters. When emulsification time increases, droplet size decreases leading to more stable emulsions. In addition, the macroscopic aspect of mixtures is mostly governed by the homogenization process as ultrasonication efficiently produces fully emulsified mixtures without creaming whereas high shear mixing does not. Therefore, the ultrasonication process is demonstrated as an efficient tool to produce homogeneous and stable Pickering emulsions without surfactant and displaying microscopic droplet sizes. It also constitutes a promising method to control parameters in industrial processes when manufacturing emulsions.