High-internal-phase emulsions stabilized solely by chitosan hydrochloride: Fabrication and effect of pH on stabilization mechanism

High-internal-phase emulsions (HIPEs) have numerous applications, particularly in the food industry, and are therefore extensively researched. In particular, the discovery of green, simple, and efficient HIPE stabilizers and the elucidation of their structure-activity relationships and stabilization mechanisms are of great practical sig-nificance. Herein, chitosan hydrochloride (CHC) was used to stabilize variable-transparency HIPEs under different conditions. At a CHC content of 0.08 wt%, one-step shear dispersion at pH 6.0-6.7 produced milky white HIPEs with small droplets (-5 mu m), high stability, strong gelation, and good plasticity, whereas highly transparent HIPEs with larger droplets (-100 mu m) were formed at pH 6.8-12.7. The stabilization mechanism depended on pH, corresponding to the formation of (i) three-dimensional (3D) reticular membranes (pH 6.0-6.7) or (ii) fibrous Pickering particles (pH 6.8-12.7). This dependence was ascribed to the effects of pH on CHC structure: CHC mainly existed as a nanofiber network with grids at pH 6.0-6.7, whereas fibrous aggregates were observed at higher pH. Thus, our study presents important insights into the pH-dependent mechanism of HIPE stabilization by CHC and facilitates the development of new emulsifiers for the formulation of variable -transparency HIPEs with diverse applications.

Automated summary

The discovery of chitosan hydrochloride (CHC) as a simple and efficient stabilizer for high-internal-phase emulsions (HIPEs) has practical significance in various applications. The stabilization mechanism of CHC is pH-dependent, with the formation of three-dimensional reticular membranes or fibrous Pickering particles.