Novel bio-based composite nanoparticles (Papain/HA-Phe) were prepared through the electrostatic interaction

hydrogen bonding and hydrophobic interaction between papain and amphiphilic L-phenylalanine ethyl ester-modified hyaluronic acid (HA-Phe).The sizes and morphologies of the composite nanoparticles were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM).The results showed that the composite nanoparticles had uniformly spherical structure with a size of 308 nm.The composite nanoparticles were used as particulate emulsifiers to stabilize white oil

forming oil-in-water Pickering emulsions.Scanning electron microscopy (SEM) characterization of emulsions demonstrated that the composite nanoparticles were adsorbed at the oil-water interface and formed the adsorption layer of composite nanoparticles to stabilize emulsions.The influences of pH values and salt on the properties of composite nanoparticles and emulsifying performances were carefully investigated.The results showed that the adsorption number of composite nanoparticles at surface of oil drops decreased and emulsifying performances of composite nanoparticles decreased with increasing pH value; the deformation degree of composite nanoparticles gradually increased and emulsifying performances increased with increasing salt concentrations.The bioactivity and inhibitory activity against tyrosinase of papain in emulsions were further investigated.The studies showed that the emulsions retained the majority of bioactivity and some inhibitory activity against tyrosinase.