Antibacterial Effectiveness of Zeolitic Imidazolate Framework-8 (ZIF-8) Nanoparticle Solutions and Its Derivatives Against Salmonella Typhimurium ATCC13311 on Loose-Leaf Lettuce (Lactuca sativa)

This study evaluated the antibacterial activity of ZIF-8, Fe-ZIF-8, and Cu-ZIF-8 at different molar ratios against Salmonella Typhimurium ATCC13311 on loose-leaf lettuce (Lactuca sativa) and compared it with the effectiveness of the standard chlorine washing method used in the fresh produce industry. Loose-leaf lettuce leaves were treated by rinsing and spraying with (1) 200 ppm chlorine, (2) ZIF-8 nanoparticle solutions, (3) Fe-ZIF-8 10%, 20%, 30%, and 40% nanoparticle solutions, and (4) Cu-ZIF-8 10%, 20%, 30%, and 40% nanoparticle solutions. Antibacterial effectiveness was determined through disk diffusion and the minimum inhibitory concentration (MIC) assays. In addition to microbiological analysis, we assessed the cytotoxicity of the materials and monitored key quality parameters of the treated lettuce, including moisture content, color, pH, and texture, during 15 days of storage at 21°C. When applied to fresh lettuce leaves, the ZIF-8-based nanoparticle treatments significantly (p < 0.05) reduced S. typhimurium contamination levels, with Cu-ZIF-8 30% achieving a 3-log CFU/mL reduction within just 2 min, surpassing the performance of standard 200 ppm chlorine treatments. ZIF-8 and Fe-ZIF-8 treatments were also more effective than chlorine. The quality of leaves was not affected (p > 0.05) when exposed to Fe-ZIF-8 and Cu-ZIF-8 solutions. However, a noticeable decline in crispness was observed after 15 days of storage at 21°C, particularly in Cu-ZIF-8–treated samples. These results support the potential application of metal-doped ZIF-8 nanoparticles as a promising alternative to conventional sanitizers for enhancing microbial safety and shelf life in fresh produce, with further optimization needed to address long-term textural effects.