In-situ dispersion of casein to form nanoparticles for Pickering high internal phase emulsions

In the present study, it was reported that 3% casein modulated by the solution pH could be an outstanding stabilizer for oil-in-water Pickering HIPEs (80% oil phase). The zeta-potential and three-phase contact angle of casein at different pH were ranged from -29 to 19 and 77 degrees to 81 degrees, respectively. Casein particles were irreversibly anchored at the oil-water interface evidenced by CLSM and cyro-SEM. The rheological properties of the HIPEs depended on casein pH and the HIPEs stabilized by casein at pH 3 displayed the greatest viscoelasticity. All the HIPEs were outstanding stable against heating (100 degrees C for 15 min), but sensitive to the frozen-thawing treatment. Casein particles on the interface provided the electrostatic repulsion and steric hindrance to prevent the coalescence or flocculation of oil drops, and interacted with casein particles with nano size in water solution for stabilizing the Pickering HIPEs. Based on the particle size of casein and the resulting Pickering HIPEs, in-situ dispersion of casein to form the oil/water interface under high-speed shearing was proposed. Food-grade Pickering HIPEs were successfully fabricated using casein.

Automated summary

The present study found that 3% casein modulated by solution pH could be an outstanding stabilizer for oil-in-water Pickering HIPEs, with control over rheological properties and enhanced stability and viscoelasticity. The casein particles at different pH levels exhibited varied zeta-potential and three-phase contact angles, indicating their irreversible anchoring at the oil-water interface. The stability of the HIPEs against heating and sensitivity to frozen-thawing treatment were also observed, highlighting the potential of casein particles for providing electrostatic repulsion and steric hindrance to prevent coalescence or flocculation of oil drops in Pickering HIPEs.