In order to prolong the shelf life of milk fan, casein-chitosan edible films incorporated with antimicrobial peptide BCp12 were prepared. One-factor-at-a-time method combined with orthogonal array design was used to determine the optimum preparation process based on elongation at break and tensile strength. The antimicrobial activity of the composite film was evaluated, and its formation mechanism was explored by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and molecular docking. Finally, the composite film was applied to the preservation of milk fan. The results showed that the optimum preparation conditions were casein/chitosan mass ratio 1:1.5, BCp12 concentration 1 mg/mL, glycerin concentration 1.5% (m/m), and drying temperature 55 ℃. SEM showed good compatibility of the composite film and FT-IR analysis revealed that the film exhibited an absorption peak at 1545.67 cm^–1 attributed to the stretching vibration of C–O. Molecular docking showed that the hydrogen bond interaction between BCp12 and casein and chitosan occurred through the active sites of residues Y4 and–NH₂. Compared with the control group, the change of peroxide value of milk fan treated with the antimicrobial film was slower and the shelf life was prolonged by 60 days during storage at 4 ℃, indicating the film could inhibit the growth of spoilage bacteria. The results of this study provide a technical reference for the development and application of chitosan-casein composite films incorporated with BCp12.

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 3313.16 and 1523.51 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.