Development of antimicrobial and antioxidant film by incorporation of modified protein self-assembled nanoparticles into Pickering emulsion

In this study, Pickering emulsion (PE) containing zein/Tannic acid (TA) nanoparticles (ZTNPs) and oregano oil (OEO) was incorporated into konjac glucomannan (KGM) film for developing active film with antioxidant and antimicrobial properties. TA anchored the amino group of zein to form covalent bond, and self-assembled to form nanoparticles via the antisolvent precipitation method. The interactions between TA and zein were characterized through FT-IR and molecular docking. The physicochemical properties and morphological characterization of ZTNPs under different zein/TA mass ratios were investigated, significant changes were observed in the Zeta-potential and particle size. ZTNP-0.2 exhibited a uniform and smooth surface (particle size≈126 nm), demonstrating exceptional antioxidant activity and highlighting the enhanced bioavailability of TA. High-speed shearing formed PE loading ZTNP-0.2 and OEO, which was applied to the preparation of active films. The oil phase was evenly distributed in the film matrix, the presence of interfaces between nanoparticles prevented flocculation and aggregation between OEO droplets, and maintained the mechanical and barrier properties of the KGM-P film. The KGM-P film demonstrated remarkable inhibitory effects against S. aureus, E. coli, and A. niger, with inhibition area diameters measuring 39.7 ± 0.46 mm, 19.92 ± 0.45 mm, and 18.70 ± 0.8 mm respectively. Furthermore, the composite KGM-P film exhibited substantial scavenging rates of 87.5% for DPPH and 89.8% for ABTS, underscoring its exceptional antibacterial and antioxidant activities. In conclusion, the active KGM film holds promise for application in food packaging, effectively extending the shelf life of products by retarding oxidation and mitigating microbial intrusion.