CORE-SHELL VS. PARTICLE STABILIZATION OF OIL-IN-WATER EMULSIONS USING CRYSTALLIZED LIPIDS: DESIGN AND STABILITY AGAINST BREAKDOWN.

Candidate: Katia Kent
Supervisor: Dr. Derick Rousseau

Abstract:

Pickering emulsions use colloidal particles for steric stabilization. Unlike typical surfactants, these particles create a solid barrier that prevents droplets from coalescing. This thesis investigated the stability of oil-in-water emulsions stabilized with crystalline CITREM (citric acid ester of monoglycerides). Emulsions were prepared by either direct solidification of CITREM at the oil-water interface forming a core-shell morphology or by adsorption of CITREM solid lipid particles, thereby producing either non-porous or porous interfacial films, respectively. Both methods yielded emulsions stable for at least one month, based on the lack of phase separation or change in average droplet size. Emulsion resilience was measured following changes in two properties of the continuous phase, namely charge screening via addition of salt (NaCl) and/or changes in polarity via addition of ethanol (EtOH). Core-shell emulsions were resistant against breakdown from charge screening up to 600 mM NaCl and when 80 and 200 mM NaCl and up to 20% EtOH conditions were added. By comparison, under the same conditions, the particle-stabilized emulsions coalesced and the emulsion phase-separated. At 800 mM NaCl and 80 wt% EtOH, both emulsions broke down, however, the particle-stabilized systems degraded to a higher extent based on changes in droplet size. These results showed how two compositionally identical emulsions differing only in the morphology of their interfacial film morphology contrasted in their ability to resist breakdown in the presence of NaCl and/or EtOH. These results offer insights for the development of novel emulsions where controlled emulsion stability or breakdown is desired.