Design and material performance of Pickering-stabilized double emulsions

There is an increased demand for low calorie and low fat foods has intensified pressure on food manufacturers to address the global obesity crisis. Double emulsions (DEs) present a promising microstructural approach to incorporate water as a fat replacement strategy. However, these complex systems are thermodynamic unstable, requiring a comprenhensive understanding of the factors influencing their stability to tailor their functionality. This thesis focuses on the creation of stable, dual Pickering-stabilized DEs, where both internal and external phases are stabilized by food-grade particles and understand their material performance. Water-in-oil (W/O) emulsions were stabilized using cocoa butter (CB)-high oleic sunflower oil-based oleogels (CBolg), which were then used as the dispersed phase in water-in-oil-in-water (W/O/W) emulsions stabilized by whey protein microgels (WPM). Results revealed that CB crystals provided remarkable stability to Pickering water droplets (up to 60 % (v/v)), preventing coalescence and phase inversion for several months. This exceptional stability was attributed to the nanoplatelet-like CB crystals in the βV polymorph at the water-oil interface and the inter-droplet fat crystal network that interlocked water droplets preventing coarsening. In addition, higher volume fraction of water enhanced the viscosity and viscoelasticity of Pickering emulsions with water droplets acting as “active fillers”. When incorporated into W/O/W emulsion, dual Pickering-stabilized DEs, facilitated by the protective layer of WPM around the external oil droplets, exhibited stability for over a month. Furthermore, CB crystals significantly reduced the friction coefficient (μ) in both emulsion types compared to pure oil when sheared in smooth, hydrophobic tribopairs. However, DEs behaves as bulk WPM when rubbed in a biomimetic tongue-like rough, soft surface, where the bigger and stable DE droplets were limited from entraining. These findings underscore the critical interplay between composition, structural arrangement, size, and surfaces in influencing stability and tribological performance. Overall, this research lays the foundation for designing sustainable, ultra-stable, low-fat emulsions with tailored functional properties, offering new opportunities for healthy food, and allied soft matter formulations.