Fabrication and stability of dual Pickering double emulsions stabilized with food-grade particles

The aim of this study was to create stable, dual Pickering-stabilized double emulsions (DEs) where both the internal and external droplets are stabilized by food grade particles. Water-in-oil (W/O) emulsions were stabilized by using cocoa butter-high oleic sunflower oil based oleogels (CBolg) and then W/O emulsion was used as the dispersed phase in water-in-oil-in-water (W/O/W) emulsions, latter stabilized by whey protein microgels (WPM). The capability of the CBolg (10 v/v% cocoa butter) to form W/O and subsequently a W/O/W emulsion was characterized using cross-polarized light microscopy, cryogenic scanning electron microscopy (cryo-SEM), confocal light microscopy (CLSM) and static light scattering. In addition, the characterization of the WPM's internal structure was evaluated by small angle X-ray scattering (SAXS). Results revealed dual Pickering stabilized W/O/W emulsions with a droplet size of 10 μm could be formed using whey protein microgel (WPM, 3-5 v/v%) as the Pickering stabilizer. Dynamic light scattering (DLS) analysis revealed WPM particles size averaging approximately 100 nm, with internal structures consisting of partially stretched protein strands with smaller compact subunits along the strand (partially folded proteins) was confirmed by SAXS analysis. The dual Pickering-stabilized DE droplets were stable over a month by formation a protective layer of WPM around the oil droplets, as observed in CLSM images, unlike the systems where the external phase was stabilized by non-microgelled whey protein, latter destabilized within hours. Such dual Pickering-stabilized DEs may offer new templates for designing healthy low-fat foods and for co-delivery of nutrients and active in multiple compartments.