Fabrication, characterization and properties of filled hydrogel particles formed by the emulsion-template method

The purpose of this study was to fabricate filled hydrogel particles based on an emulsion-templating method that could be used as delivery systems. An oil-in-water-in-oil (O/W/O) emulsion was produced using a 2 step process: (i) an O/W emulsion was produced by high pressure homogenization of an oil phase with a water phase containing whey protein isolate (15% WPI, 100 mM NaCl, pH 7); (ii) an O/W/O emulsion was produced by high shear mixing of the O/W emulsion with another oil phase. The O/W/O emulsion was then thermally processed (90 °C, 30 min), which caused the whey protein molecules to unfold and form a hydrogel in the water phase. The filled hydrogel particles (O/W) were isolated from the O/W/O emulsion by washing with n-hexane. These particles could be dispersed in aqueous solutions containing hydrophilic emulsifiers to inhibit aggregation. Confocal microscopy and spectroscopy measurements indicated that a high percentage of the internal oil phase remained encapsulated in the whey protein hydrogel particles (>94%). During storage for 7 days at room temperature, there were no changes in the size or charge of the filled hydrogel particles. The results suggest that emulsion templating could be a suitable process of encapsulating and protecting labile lipids using hydrogel particles.