Correlation study between structural parameters of droplets and rheological properties of O/W high internal phase Pickering emulsions above the closest packing density

The correlation between the structural parameters of droplets and rheological properties of O/W high internal phase Pickering emulsions (HIPPEs) stabilized by soy protein isolate (SPI) nanoparticles was elucidated, with a volume fraction of dispersed phase (ϕ) above the closest packing density (74%). The structural basis of SPI nanoparticles was confirmed to be spherical heat-induced protein aggregates, which had moderate wettability and excellent interfacial activity. The structural parameters of emulsion droplets (contact length L, diameter D, length d1, width d2, the number of adjacent contact droplets Z), and the stability and rheological properties of HIPPEs were characterized by the confocal laser scanning microscopy (CLSM), diffusing wave spectroscopy (DWS), and mechanical rheometer respectively. The results of CLSM indicated the transition of droplets from spherical to polyhedral shapes as increased ϕ, accompanied by an increased L and Z. The rheological and stability analysis confirmed the widened linear viscoelastic range, elevated gel point (εc), and the extended half−life of the intensity autocorrelation function of HIPPEs as ϕ increased. Moreover, the loss factor (tan δ) remained constant at 0.1 within the ϕ of 74%–86%, revealing the solid−like nature of HIPPEs. The correlation between ϕ, structural parameters of droplets, and rheological properties of HIPPEs was further analyzed. The nonlinear regression fitting between the L/D and G' (elastic modulus) yielded a better fitting effect than d1/d2 and Z, suggesting an intrinsic correlation between emulsion structure and rheology. In summary, this study elucidated the intricate relationship between ϕ, droplet structure, and rheological properties of HIPPEs, offering a research foundation and theoretical basis for the development and application of protein particle−stabilized HIPPEs.