In-vitro Digestion Of Fat Crystal-Stabilized Water-In-Oil Emulsions

The purpose of this research was to investigate the effect of surfactant type and presence of solid fat on the stability and release characteristics of water-in-oil (W/O) emulsions subjected to simulated gastrointestinal conditions. Emulsions consisting of a 20 wt% aqueous phase dispersed in canola oil were stabilized in one of four different ways: core-shell stabilization with glycerol monostearate (GMS), network stabilization using polyglycerol polyricinoleate and solid fat added to the continuous phase (PGPR-F), combined core-shell and network stabilization using glycerol monooleate and a continuous phase fat crystal network (GMO-F) and finally, a PGPR-based liquid emulsion with no added fat. The dispersed aqueous phase of all emulsions contained 1mM methylene blue (MB), which was used as a marker to quantify emulsion breakdown and release of aqueous phase cargo. Quiescent storage at 25 °C for 30 days revealed no phase separation for the GMS, GMO-F, and PGPR-F emulsions whereas the PGPR emulsion began to phase-separate 16 h following preparation. When subjected to gastric conditions, the PGPR-F emulsion showed the lowest MB release after 60 min (0.3 % of initial load) with the other emulsions showing ~ 12 % release. In duodenal conditions, the PGPRF and GMS emulsions showed the lowest MB release after 120 min of exposure (~ 0.5 %) followed by the PGPR (9.4 %) and GMO-F (14.6 %) emulsions, respectively. Emulsion photomicrographs taken prior to, and after, contact with simulated gastric and intestinal fluids showed that emulsion microstructure was an important contributor to emulsion stability. Overall, the PGPR-F emulsion was the most stable in both gastric and intestinal fluids. These results have shown that fat phase structuring is an important contributor to W/O emulsion breakdown behaviour in simulated gastrointestinal conditions.