Stability of protein particle based Pickering emulsions in various environments: Review on strategies to inhibit coalescence and oxidation

Abstract

The emerging research interests in fabrication of protein particles as soft-particle emulsifiers show the prospective potential of using protein particles in novel poly-phase dispersing food systems. This review first provides a comprehensive summary and analysis on the dominant role of key physicochemical properties of protein particles including wettability, morphology, surface charge and protein concentration on their emulsifying abilities to construct Pickering emulsions. It was found that the constructed emulsions showed high sensitivity to changes in pH, ionic strength and temperature (thermal and freeze-thaw treatment). Moreover, oxidation remains as a challenge for protein particle based Pickering emulsions during prolonged storage, reducing their acceptance in food products. Current strategies for improving the stability of these emulsions to variable aqueous conditions and variable temperatures, and restricting oxidation event are summarized. In summary, an "ideal" protein particle-based Pickering emulsion system is proposed, encompassing aspects of interfacial property, emulsion network and texture, and antioxidant enrichment, thus promoting industrial translation into novel food and nutraceutical products.

Keywords: Interface; Oxidation; Pickering Emulsion; Protein particle; Stability.

Fig. 1

The characteristics of protein particles influencing the interfacial properties and the responsiveness to environment of the constructed HIPEs.

Fig. 2

Typical three-phase contact angles (A) and the simulated oil–water interface of hydrophobic protein, hydrophilic polysaccharide and the protein-polysaccharide complex.

Fig. 3

Simulation of ovabumin stabilized HIPEs classified to three types as effected by protein concentration.

Fig. 4

The simulated microstructure of PPEs prepared at pH value close to or far away from pI, showing the droplets and interface stabilized by dispersed or flocculated protein particles.

Fig. 5

Schematic illustration of the effect of NaCl on the formation of gel-like network of protein particle-stabilized Pickering emulsions and the enhancement of freeze–thaw stability.

Fig. 6

The simulated desirable structures of PPEs with excellent antioxidant capacity.