Dispersed droplets as tunable fillers in water-in-oil emulsions stabilized with fat crystals

The role of water droplets as rheology modifiers in fat crystal-stabilized emulsions is not widely studied, but relevant to many fields and industries such as foods and cosmetics. The degree to which water droplets interact with the surrounding fat crystal network can impart a significant effect on rheology. The objective of this study was to investigate how the rheology of water-in-oil (W/O) emulsions stabilized by a surrounding fat crystal network is impacted by the ability of emulsifiers that promote interfacial fat crystallization and whether droplet size is a contributing factor. Three emulsifiers imparting different interfacial characteristics were chosen: glycerol monooleate (GMO) and glycerol monostearate (GMS) both promoted interfacial crystallization in the presence of hydrogenated soy oil (HSO) whereas polyglycerol polyricinoleate (PGPR) did not. Different homogenization methods were used to create emulsions with two distinct average droplet sizes with narrow size distributions for each emulsifier. Amplitude sweeps showed that GMS emulsions, independently of droplet size, displayed the highest elastic modulus (G') values followed by GMO, and then PGPR. Reinforcement (R'= G'(emulsion)/G'(HSO network)) values increased with each emulsifier over time, but its extent was dependent on emulsifier-mediated droplet-droplet interactions. In both GMO and GMS-stabilized emulsions, smaller droplets enhanced reinforcement whereas the opposite was observed in PGPR-stabilized emulsions. This study has shown that, through the use of different emulsifiers, the droplet interface should be considered a functional component that can used to tailor the consistency of fat crystal-stabilized W/O emulsions.