The effect of weakly charged insoluble karaya gum (KG) on zein colloidal nanoparticles (ZKGPs) for stabilizing Pickering emulsions was investigated. Due to weak surface charge, KG could cover the surface of zein particles by hydrogen bonds and weak electrostatic interactions. With the increase in coverage, the zeta potential of ZKGPs changed from positive to negative values close to zero and the average particle size tended to become larger. The closest neutral wettability (89.85°) was achieved when the zein/KG mass ratio was 1:1. The samples prepared with high oil volume fraction (φ = 0.5-0.75) and high particle concentration (1.0-1.3 %, w/v) formed emulsion gels easily and showed higher storage stability. CLSM images also confirmed that ZKGPs could be distributed in the continuous phase to enhance the emulsion network structure. Consequently, weakly charged ZKGPs reduced the emulsification energy barrier and increased the coverage and steric hindrance of particles at the oil/water interface. These findings provide new ideas for the development of stable Pickering emulsions for application in food textural modification as well as encapsulation and delivery of bioactive substances.
Keywords: Karaya gum; Microstructure; Pickering emulsions; Weakly charged nanoparticles; Zein.
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