Dispersed droplets as active fillers in fat-crystal network-stabilized water-in oil emulsions

We show that the rigidity and microstructure of water-in-oil (W/O) emulsions depend on the ability of oil soluble emulsifiers to enhance the crystallization of fats on the surface of dispersed aqueous droplets. In test emulsions consisting of hydrogenated soy oil (HSO) in liquid canola oil (CO) and a dispersed aqueous phase representing up to 20 wt% of the emulsion, use of glycerol monooleate (GMO) promoted oil-water interfacial crystallization whereas polyglycerol polyricinoleate (PGPR) resulted in HSO crystallization in the continuous phase only. By removing the confounding effects of droplet size and solid fat content, GMO-covered emulsion droplets were shown to behave as active fillers as they interacted with the surrounding fat crystal matrix and increased emulsion rigidity. By contrast, the PGPR-stabilized droplets only weakly associated with the matrix and did not significantly alter emulsion rheology, hence these were inactive fillers. This study shows that by simply changing emulsifier type, it is possible to alter the magnitude of the association between the dispersed droplets and surrounding fat crystals and, by extension, tailor the texture and rigidity of fat crystal-stabilized water-in-oil emulsions.