Characterization of oil-in-water pickering emulsions stabilized by β-cyclodextrin systems

Abstract

Cyclodextrins (CDs) are conical molecules with a hydrophilic surface and a hydrophobic cavity. Thanks to the cavity, CDs are able to form inclusion complexes with a wide variety of guest molecules. A new oil-in-water (O/W) emulsifying system suitable for use in preparing Pickering emulsions with a large range of oils was developed. This system contains β-Cyclodextrin (β-CD) and a natural origin selected surfactant, Polyglyceryl-3 diisostearate (PG3D). The purpose of this work is to better understand the role of the PG3D in the realization and stabilization of these O/W emulsions. With this aim, O/W Pickering emulsions stabilized only by β-CD or β-CD/PG3D blends were prepared, and the effects of the presence of PG3D at different levels on the stability of emulsions were investigated. This original work was implemented using a wide range of complementary analytical methods, especially tensiometry, optical microscopy, laser granulometry, classical NMR and low field NMR measurements. The effectiveness of the β-CD/PG3D emulsifying system for preparing O/W Pickering emulsions appears due to synergistic effects between β-CD and PG3D. These molecules are both acting to stabilize the oil/water interface. The created particles have a high affinity for water with about the same contact angle as found for water. This may explain that only O/W emulsions are obtained using this system as in the case of using β-CD alone. PG3D by decreasing interfacial tension and due to its high wettability of the hydrophobic surfaces helps to get finer emulsions. An optimum β-CD/PG3D ratio must be used to obtain the most stable emulsions.