Insight into oil-water interfacial behaviors of whey protein isolate and sterol towards stabilizing high internal phase Pickering emulsion gels

Abstract

This investigation elucidated stabilization of high internal phase Pickering emulsion gels (HIPPEGs) on the basis of oil-water interfacial adsorption properties of particles. The particles were prepared by whey protein isolate (WPI) and two structurally different sterols, including ergosterol (ES) and γ-oryzanol (γS). Initially, oil-water interfacial adsorption properties were improved in the presence of sterol. And WPI-γS exhibited higher contact angle and lower dynamic interfacial tension than WPI-ES. Quartz crystal microbalance with dissipation monitoring measurement further proved that adsorption mass and viscoelasticity of WPI-γS was higher than those of WPI-ES. Furthermore, WPI-sterol HIPPEGs showed lower average particle size and moisture content, higher absolute value of ζ-potential than WPI-stabilized HIPPEGs. Apparent viscosity, storage modulus and loss modulus of WPI were improved after the addition of sterol. Moreover, WPI-γS HIPPEGs exhibited higher stabilities and viscoelasticity than WPI-ES HIPPEGs. Additionally, compared with WPI-stabilized HIPPEGs, WPI-γS-loaded HIPPEGs showed shorter relaxation time and more uniform color distribution, indicating that droplet flow was restricted and more uniform, followed by WPI-ES-loaded HIPPEGs. Finally, super-resolution microscope results exhibited that sterol inhibited emulsion droplets aggregation due to steric hindrance. HIPPEGs stabilized by WPI-γS showed more homogeneous and smaller droplets than WPI-ES-loaded HIPPEGs. This work provided a theoretical support for stable HIPPEGs formed with protein-sterol particles, which would be applied to replace trans fats and cholesterol in various food products.