Surface coating of zein nanoparticles to improve the application of bioactive compounds: A review

As an excellent delivery material for bioactive compounds, zein nanoparticles are limited by colloidal instability. Recently, the development of their surface coating has greatly promoted the performance of the zein-based delivery system. In the future, surface-coated zein nanoparticles delivering bioactive compounds will have broader applications in the food industry. This review focuses on introducing different methods and materials of surface-coated zein nanoparticles and their encapsulated bioactive compounds, including the assessments for the improved application of these compounds. Additionally, the application in food-related fields is summarized. Finally, some challenges regarding the surface coating of zein nanoparticles and development trends are presented. Currently, methods for surface coating of zein nanoparticles include antisolvent precipitation, antisolvent co-precipitation, layer-by-layer, solvent evaporation, and pH-driven. The materials are mainly proteins, polysaccharides, surfactants, and their composites. It can not only deliver a single bioactive compound but also achieve co-delivery. The evaluation of the improved compound application includes physical and chemical stability, controlled release/bioaccessibility, and biological activity. Moreover, surface-coated zein nanoparticles can be applied to Pickering emulsions and edible films. There are also some challenges in surface coating development. The future will be to improve the application of zein carriers in commercial products, and laboratory-level researches including new system development, smart co-delivery design, and bioavailability mechanism. In conclusion, surface coating of zein nanoparticles have a bright prospect to improve the application of bioactive compounds in the food industry.