Fabrication and characterization of novel Pickering emulsions and Pickering high internal emulsions stabilized by gliadin colloidal particles

Abstract

In this paper, we demonstrate for the first time the use of gliadin colloid particles (GCPs) as an effective particulate stabilizer of oil-in-water emulsions of natural oils and water. For this purpose, we fabricated GCPs through a facile anti-solvent precipitation procedure and demonstrated their uses in the formation of Pickering emulsions as well as Pickering high internal phase emulsions (HIPEs). We found that unmodified GCPs can produce stable, surfactant-free o/w emulsions with microscale droplet sizes under experimental mixing conditions at pH 4 and above. In contrast, the emulsions were not stable against coalescence at ∼pH 3.0. The microstructures, e.g., interfacial framework, GCPs partition between the continuous phase and interfacial region, and state of the droplets, of Pickering emulsions as a function of pH were visualized by optical microscopy and confocal laser scanning microscopy (CLSM), confirming that in addition to Pickering stabilization, the GCPs-based network and/or dispersed droplets-based network also contributed to the stabilization of the emulsions, in a pH-dependent manner. Clear correlations exist between colloid properties of the GCPs dispersions and the emulsion characteristics. Interestingly, stable surfactant-free Pickering HIPEs were fabricated by a facile shearing emulsification. This study opens a promising route based on Pickering HIPEs to transform liquid oils into viscoelastic emulsion gels with zero trans-fat and less saturated fat. The Pickering HIPEs possess promising potentials to replace solid fat in food formulations, which outline new directions for future fundamental research.