Tuning the molecular interactions between gliadin and tannic acid to prepare Pickering stabilizers with improved emulsifying properties

Amphiphilic plant proteins, such as the wheat gliadin and maize zein, are good starting materials to fabricate colloidal particles for stabilizing foams and emulsions. Like many other food proteins, the emulsifying property of the gliadin can be modified by introducing polysaccharides; however, little to nothing is known about how it was influenced by the protein-polyphenol interactions. In this study, different gliadin/tannic acid nanoparticles (GTNP) were developed and assessed for their capacity to stabilize an oil-in-water emulsion at a low solid concentration (0.1%, w/v). More than simply mixing these two components, both noncovalent and covalent (alkali-triggered) interactions were induced between the tannic acid (TA) and gliadin. Results indicated that emulsions stabilized by the covalent GTNP exhibited greatest resilience to coalescence and most reduced mean particle diameters over a 30-day storage period. In addition, the covalent GTNP showed intermediate wettability at the oil/water interface, as reflected by the oil-water contact angle of 89.1°, which contributed to the emulsifying properties. Our experiments that tuning the covalent and noncovalent interactions between the gliadin and TA provide novel insights into the interfacial behaviors of protein-polyphenol nanoparticles, particularly as food-grade Pickering emulsifiers.