Encapsulation of water-in-oil emulsion droplets within crystal spheroids

Abstract

Model water-in-oil emulsions were shear-crystallized to produce crystal spheroid-encapsulated droplets. The bulk oil phase was composed of canola oil (CO), fully-hydrogenated canola oil (FHCO), and different emulsifiers: glycerol monostearate (GMS), glycerol monopalmitate (GMP), glycerol monooleate (GMO), sorbitan monostearate (SMS), or polyglycerol polyricinoleate (PGPR). Emulsions were prepared using a rotor-stator and then further shear-crystallized using a rheometer with a parallel plate geometry. The efficacy of water droplet encapsulation was dependent on emulsifier type, with the glycerol-based emulsifiers (GMS, GMP, and GMO), due to their molecular similarity with the crystallizing phase (FHCO), producing smooth-surfaced crystal spheroid shells while SMS produced irregularly-shaped crystal shells and droplet cores. PGPR-based emulsions did not exhibit droplet encapsulation due to the emulsifier's large molecular difference to the crystallizing phase. Analysis of viscosity profiles, thermal behavior, and X-ray diffraction revealed that the addition of an aqueous phase did not significantly affect crystal polymorphism. These results serve as a foundation for the development of novel emulsions systems for use in industries where effective water droplet encapsulation is necessary for optimum product performance.