The microstructure and physiochemical stability of Pickering emulsions stabilized by chitosan particles coating with sodium alginate: Influence of the ratio between chitosan and sodium alginate

Abstract

The purpose of this study was to further improve the physiochemical stability of the chitosan (CS) particle-stabilized Pickering emulsion by coating with sodium alginate (SA). The effect of different mass ratios of CS and SA (1:0.5-1:2) on the microstructure, rheology and the stability of the emulsions were comprehensively evaluated by various methods such as optical microscope, scanning electron microscope, rheometer, and low-field nuclear magnetism. The multilayer emulsion with low content of SA (CS:SA = 1:0.5) presented bridging flocculation. If SA concentration was high (CS:SA = 1:1-1:2), the surface of the Pickering emulsion droplets was completely covered by the SA. At this time, multilayer emulsion droplets became stable due to strong electrostatic and/or steric repulsion. Too high SA concentration (CS:GA = 1:2) might also promote the accumulation of moisture. In addition, the CS/SA multilayer emulsion showed higher coalescence stability under different environmental treatments but its creaming stability and flocculation stability were still sensitive to pH (2, 4 and 10), temperature (4 °C and 80 °C) and ionic strength (300-500 mM). In all, the addition of the proper level SA (CS:GA = 1:1-1:2) could increase the stability of CS particle-stabilized Pickering emulsion.

Keywords: Chitosan; Multilayer emulsion; Pickering emulsion; Rheology; Sodium alginate; Stability.