Multi-Ion Zeolite-Based Antimicrobial LDPE Films for Active Food Packaging: Ion Combinations and Performance in Real...

Inorganic ion-based antimicrobial systems have been widely investigated; however, the rational design of multi-ion systems that combine distinct antimicrobial mechanisms while remaining compatible with thermoplastic processing for practical and potentially more sustainable active packaging solutions remains limited. In this study, a multi-ion zeolite-based antimicrobial system was designed by immobilizing selected metal and non-metal cations (Zn^{2 +}, Mg^{2 +}, Ca^{2 +}, Si^{4 +}, Fe^{3 +}, Ti^{4 +}, and Al^{3 +}) according to their reported antimicrobial mechanisms. The antimicrobial activities of individual ions and their combinations were evaluated using minimum inhibition concentration and minimum lethal concentration analyses against Escherichia coli and Staphylococcus aureus, indicating improved antibacterial performance for multi-ion combinations compared to single-ion systems. The ion-immobilized zeolite was incorporated into low-density polyethylene (LDPE) films at 1 wt% via twin-screw extrusion and film-blowing processes. Structural incorporation of the antimicrobial system was examined using FT-IR and SEM-EDS analyses. Mechanical properties of the resulting films were not significantly altered compared to neat LDPE, demonstrating compatibility with conventional polymer processing. The antibacterial performance of the films was evaluated under controlled contact conditions and in a model high-moisture biological system at 10°C and 30°C. Under these conditions, where LDPE films containing the multi-ion zeolite exhibited greater bacterial reduction than films containing zeolite alone. This study presents a mechanism-based strategy for designing multi-ion antimicrobial systems and their incorporation into thermoplastic polymer films, providing a basis for further investigation under application-relevant conditions. PRACTICAL APPLICATIONS: This research shows that combining multiple antimicrobial ions in zeolite can improve the antibacterial performance of plastic packaging films without changing how the films are manufactured. The developed LDPE films kept their original strength and flexibility while reducing bacteria on food-contact surfaces, including moist foods such as fresh produce. This approach may help manufacturers develop antibacterial packaging materials using existing plastic processing equipment.