Fabrication and characterization of novel high internal Pickering emulsions stabilized solely by ultrafine pearl powder

Abstract In this work, we reported that ultrafine pearl powder could perform as an outstanding stabilizer for oil-in-water high internal phase Pickering emulsions (HIPPEs). Comparing with pearl powder (PP), the emulsifying property of ultrafine pearl powder (UPP) treated by physical milling was greatly improved, which enabled it to stabilize higher volume of oil phase and form smaller emulsion drops. The concentration of UPP in the continuous phase for the formation of homogenous and gel-like HIPPEs could be as low as 0.5 wt%; and increasing the concentration from 0.5 to 3.5 wt% led to a progressive decrease in droplet size. High centrifugal stable HIPPEs were formed at pH values of 9.3–10.0, and decreasing the pH increased the emulsion size. Furthermore, two-step method which 1/3 vol of oil phase was added in the first step at a lower homogenizing speed can be used to produce gel-like HIPPEs at the oil content (ϕ) values of 0.89 which stabilized by 1.5 wt% of UPP, whereas one-step method can only produce at ϕ = 0.87. This is presumably due to a better distribution of UPP and the accumulation deformation between the emulsion droplets, resulting in the high concentration of droplets can be produced by two-step method efficiently. These findings would be of importance not only for the fabrication of Pickering HIPPEs stabilized by biological particles, but also for the development of novel, eco-friendly and sustainable HIPPEs for food, cosmetic and medicine formulations.