Surface Heterogeneity at the Polymer–Food Interface Influences Ag Migration from Plastic Packaging Incorporating Ag-Exchanged Zeolites

Silver-enabled polymers, with their antimicrobial properties, could prolong the shelf life and maintain quality in packaged foods. However, there is limited understanding about how the Ag form in the polymer, food chemistry, and other factors affect the transfer (migration) of Ag from the polymer to the food under the intended conditions of use. In this study, we investigated the release of Ag from polymer composites (PCs) incorporating two different Ag-exchanged zeolites (Ag-Y), which have been explored as potential scaffolds for loading high concentrations of Ag within common polymers. We manufactured two Ag-Y films based on low-density polyethylene (LDPE): one incorporating ionic Ag (Ag⁺) and one incorporating nanoparticulate Ag (AgNPs), each with similar initial Ag concentrations. Then, we assessed the migration of Ag out of these PCs into food simulants under accelerated room temperature storage conditions. In all simulants investigated, the Ag⁺-Y/LDPE film exhibited a higher migration of Ag compared to the AgNP-Y/LDPE film, suggesting a lower fraction of readily releasable Ag in the latter material. Total Ag migration from AgNP-Y/LDPE over 10 days at 40 °C was 11.10 ± 2.05 ng cm^-2 of packaging surface area in water, 7.63 ± 1.59 ng cm^-2 in a 9 wt % aqueous sucrose solution, and 21.29 ± 1.98 ng cm^-2 in a commercial sweetened carbonated beverage (Squirt). In contrast, Ag migration from Ag⁺-Y/LDPE was measured at 49.61 ± 3.46, 57.48 ± 9.65, and 91.54 ± 5.58 ng cm^-2 in water, sucrose solution, and Squirt drink, respectively. Surface characterization techniques, including atomic force microscopy (AFM), scanning electron microscopy (SEM), and conductivity measurements, revealed the presence of exposed zeolite particles at the surface of the films, suggesting that direct interactions between Ag-exchanged zeolites and food components at the simulant-polymer interface play an important role in determining Ag migration from Ag-Y/LDPE PCs.