Monodisperse Plant Protein Nanoparticles Prepared by Cation-Exchange Resins for Stabilization of Pickering Emulsions

Our understanding of the microstructure of many plant proteins is based on the ancient and conventional methods of alkali extraction and acid precipitation, which generate considerable amounts of NaCl causing salting-out effects and aggregation of their molecules. In this study, monodisperse rice protein (RP) nanoparticles were prepared using cation-exchange resins that release H⁺ and absorb Na⁺, thus avoiding the generation of NaCl during neutralization of the alkali extracts. The generated RP nanoparticles of small diameter (20 nm) and excellent uniformity (0.17 polydispersity) quickly diffuse to and stabilize the oil-water interface, producing oil-in-water Pickering emulsions. The emulsifying ability and emulsion stability afforded with these nanoparticles were 17 and 3.5 times higher than those of nanoparticles prepared by conventional alkali extraction and acid precipitation methods, respectively. Furthermore, increased RP nanoparticle concentration created more stable emulsions with smaller droplets and reduced flocculation index vital for practical applications. This study provides a convincing example of how to prepare monodisperse protein nanoparticles that adsorb at a fluid interface, which may find numerous applications in food and cosmetic formulations.