Abstract: This study was undertaken in order to improve the stability, water solubility and gastrointestinal release of phytosterols (PS). Zein-PS nanoparticles were prepared by the anti-solvent method. Single factor experiments and orthogonal array design methods were adopted to optimize the preparation conditions based on the stability and encapsulation efficiency of zein-PS nanoparticles. The structure and functional properties of the prepared samples were characterized by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and simulated gastrointestinal digestion. The results showed that the optimal preparation conditions were determined as follows: zein/PS ratio of 15:1 (m/m), hydration time of 2 h, hydration temperature of 55 ℃, and ultrasonic treatment time of 20 min. The encapsulation efficiency of the nanoparticles prepared using the optimal conditions was 84.97%, particle size (479.76 ± 0.38) nm, and zeta potential (−22.79 ± 0.015) mV, suggesting small particle size and high stability. The nanoparticles with a zein/PS ratio of 15:1 had better re-solubility and water solubility. SEM revealed the formation of a compact network structure on the surface of the nanoparticles and FTIR spectra showed that it changed at 3 313.16 and 1 523.51 cm-1, indicating the presence of hydrogen bonding and electrostatic interaction between zein and PS. Compared with PS, the release rates of the nanoparticles in simulated gastrointestinal fluids were reduced by 49.03% and 28.11%, respectively, showing a good sustained-release effect. In addition, after storage for 30 days, the change in the particle size of the nanoparticles was smaller at 4 ℃ than at 25 ℃, and the encapsulation efficiency remained above 70%. Therefore, zein-PS composite nanoparticles have good stability and sustained release property, which has potential application prospects in the food industry.

Key words: zein; phytosterol; nanoparticles; sustained release property