Abstract: The interaction between quercetin (Q) and wheat gliadin (G) under different pH conditions were studied by fluorescence spectroscopy. The properties of Pickering emulsions stabilized by G or G-Q complexes were investigated. The results showed that under all pH conditions tested, the fluorescence of G was quenched by Q in both dynamic and static modes, mainly through hydrophobic interaction for pH 3.0, and hydrogen bonds and van der Waals forces for pH 5.0 and 7.0. Scanning electron microscopy showed that the protein could more easily form a compact and dense reticular structure with increasing pH. Differential scanning calorimetry demonstrated that protein molecule denaturated in a more collaborative manner at pH 5.0. The emulsion stabilized by G-Q complex at pH 5.0 possessed the highest viscosity and strongest gel performance. The emulsion was stable without oil deposition during storage for 90 days. At pH 3.0, the continuous network structure of protein particles in the continuous phase greatly contributed to the stability of the emulsion, while at pH 5.0, the interaction between particles adsorbed at the interface between oil droplets and water and the interaction between oil droplets stabilized the emulsion.

Key words: wheat gliadin; quercetin; interaction; Pickering emulsion; rheological properties