Abstract: 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 1 545.67 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.

Key words: edible film; antimicrobial peptide BCp12; molecular docking; preservation of milk fan