# Structure–Activity Relationship and Stability Mechanism of Pickering Emulsions Stabilized by Gorgon Euryale Starch–Quinoa Protein Complex Under pH Regulation

## TL;DR

This study explores how pH affects the stability and structure of emulsions made with a starch-protein complex from gorgon euryale and quinoa.

## Contribution

The study reveals the stability mechanism and structure–activity relationship of emulsions under different pH conditions.

## Key findings

- Emulsions at pH 3 showed the highest hardness and viscosity but weakest cohesiveness.
- Emulsions at pH 3 remained stable at 60 °C and had fine, uniform droplets.
- pH 11 emulsions had low viscosity due to macromolecular structure destruction.

## Abstract

This study investigated the effects of pH (3, 5, 7, 9, 11) on the structure–activity relationship and stability mechanism of Pickering emulsions stabilized by the gorgon euryale starch–quinoa protein complex. Analyses were performed using reverse compression test, rheology, thermal stability assessment, atomic force microscopy (AFM), and low-field nuclear magnetic resonance (LF-NMR) measurements. Reverse compression test showed that the emulsion at pH 3 exhibited the highest hardness and consistency, but the weakest cohesiveness. Rheological measurements revealed that all emulsions displayed shear-thinning behavior, the emulsion at pH 3 had the highest shear stress and apparent viscosity, while that at pH 11 showed the lowest viscosity due to the destruction of macromolecular structures. Thermal stability assessment indicated that the emulsion at pH 3 did not undergo significant stratification even at 60 °C, whereas the stability of emulsions decreased between pH 5–9. Microscopic analyses (optical microscopy, AFM, and LF-NMR) further confirmed that the emulsion at pH 3 had fine, uniform droplets, strong water-binding capacity, and an interfacial film with a “dense protrusion” structure. This study provides a basis for the environmental adaptability design of functional emulsions and contributes to the high-value utilization of gorgon euryale and quinoa resources.