Oil-water interfacial behavior of soy protein nanoparticles in high internal phase Pickering emulsion

We investigated the interfacial properties of soy protein isolate (SPI) heat aggregation nanoparticles (SPN) at the oil-water (O/W) interface, as well as the preparation and rheological properties of high internal phase Pickering emulsions (HIPPEs). Increasing the concentration of SPN led to a reduction in the dynamic interfacial tension (γ) and facilitated the diffusion and permeation processes. The interface became adsorbed by a multilayer protein film, reaching almost saturation, which hindered further rearrangement processes between SPNs. SPN formed a viscoelastic film at the O/W interface, with the interfacial viscoelastic modulus (E) proportional to the SPN concentration, resulting in thicker and stronger interface films. For SPN films with concentrations of 0.2–1.5 wt%, strain hardening was observed during compression and strain softening during extension under relatively large amplitudes (>20%). Conversely, films with concentrations of 2.0–3.0 wt% exhibited a linearly elastic response. Optical microscopy of SPN-stabilized HIPPEs and droplet surface cryo-scanning electron microscopy (cryo-SEM) indicated that increasing SPN concentration improved interface properties. Furthermore, rheological results on HIPPEs revealed that higher SPN concentrations enhanced viscoelasticity and emulsion recovery. These findings deepen our understanding of soy protein particle adsorption at the O/W interface and the rheological implications for HIPPEs applications.