Water-In-Oil Pickering Emulsions Stabilized by MicrocrystallinePhytosterols in Oil: Fabrication Mechanism and Application as a SaltRelease System

Recently, Pickering emulsions stabilized by edible particles have attracted significant attention from the scientificcommunity and food industry owing to their surfactant-free character. However, those edible particles are mostly used for stabilizingoil-in-water emulsions, whereas those for water-in-oil emulsions are very limited. In this article, stable water-in-oil Pickeringemulsions were prepared through dispersing phytosterol particles in oil phase, and the effects of antisolvent treatment, the type of oil,particle concentration, and water fraction on the stability, type, and morphology of these emulsions were investigated. In addition,the release profile of salt as a model aqueous compound from these emulsions has also been studied. Results showed that due to itshigher water content, the antisolvent pretreatment of phytosterol in the ethanol/water system facilitated the dispersion of driedphytosterol particles into oil phase as microcrystals. Water-in-oil Pickering emulsions with droplet sizes of 80-100 mu m werefabricated at phytosterol concentrations of 1.5-3% w/v and water fractions of 0.2-0.6. The dissolved phytosterol molecules in oilphase could help in emulsion stabilization through interfacial crystallization during emulsification, evidenced by polar microscopicobservations. Moreover, the salt release from phytosterol-stabilized Pickering emulsions showed a temperature-dependent profilewhich could have potential application in a controlled-release system. The current study provided important information forfabrication of stable water-in-oil emulsion using natural particles.