Water-in-oil Pickering emulsions stabilized by phytosterol/chitosan complex particles

The development of colloidal particles for the preparation of water-in-oil (w/o) Pickering emulsions is highly desirable for food, pharmaceuticals, and cosmetics. However, the lack of bio-based hydrophobic particulate stabilizers makes it remain a great challenge. Herein a water-in-cyclopentasiloxane (w/o) Pickering emulsion was prepared using phytosterol/chitosan (PS/CS) complex particles as the stabilizer. Adsorption of CS onto the surface of PS particles via electrostatic interaction changed the particle wettability and interfacial activity, leading both PS particles and CS to be absorbed at the w/o interface. By varying the pH and ionic strength of aqueous phase, the stabilizing mechanism was verified and the results suggested that the formation of PS/CS complex particles was critical in the preparation of w/o Pickering emulsions with small and uniform droplets. The PS/CS complex particles can emulsify a broad range of water volume fraction and even be used to prepare a high internal phase w/o Pickering emulsion. Meanwhile, the as-prepared w/o Pickering emulsions had good long-term stability, especially at ambient or lower temperature. Finally, we demonstrated that the prepared w/o Pickering emulsion could effectively protect encapsulated epigallocatechin gallate from heat and pH shock.