General liquid vegetable oil structuring via high internal phase Pickering emulsion stabilized by soy protein isolate nanoparticles

Oil structuring has attracted immense interest in the last decades because it can transform liquid oils into elastic semi-solids, which has been widely used in material science, pharmaceutical industry, and food processing. However, the facile conversion of liquid vegetable oils into soft matters without changing their intrinsic nature is challenging. Here we report a general approach for structuring liquid vegetable oils by a high internal phase Pickering emulsion (HIPPE) stabilized by edible soy protein isolate (SPI) nanoparticles. SPI nanoparticles with moderate amphipathy (θ = 90.7°) and size (∼187 nm) were obtained via the heat-induced aggregation of native SPI. These SPI nanoparticles possessed excellent interfacial activity and emulsion stabilization ability and thus were suitable for preparing edible HIPPEs from diverse liquid vegetable oils. The effect of internal volume fraction (ϕ) and particle concentration, stability, and rheology of Pickering emulsions were studied. Particularly, the role of intrinsic surfactants (e.g., lecithin) in vegetable oils on the interfacial and macro rheology of the system was highlighted. Compared with native SPI, SPI nanoparticles endowed the HIPPEs with improved stability (>14 days), high interfacial pressure (>2 mN/m), and high elastic modulus (>900 Pa). Moreover, the HIPPEs stabilized by SPI nanoparticles exhibited a good ability to structure various vegetable oils, depending on oil types and ϕ. We envisage that this biomass-mediated HIPPE system provides a promising strategy to structure various liquid vegetable oils, significantly facilitating sustainable development.