Antibacterial Activity of Low-Density Polyethylene and Low-Density Polyethylene-co-maleic Anhydride Films Incorporated with ZnO Nanoparticles

This study innovatively produced polymeric active antibacterial films by incorporating zinc oxide nanoparticles (ZnO-NP) into linear low-density polyethylene grafted with maleic anhydride (LLDPE-MA) and low-density polyethylene (LDPE) using polymer melting and coating of ZnO-NP. It was evaluated the physical properties and antibacterial effects against foodborne pathogens (Staphylococcus aureus, Salmonella Typhimurium, and Pseudomonas aeruginosa) by liquid and disk-diffusion in agar tests. The active films presented 1.0, 2.5, and 5.5% of ZnO-NP. The two with higher ZnO-NP content presented similar antibacterial activity, demonstrating that the ZnO-NP availability on the film surface is more important than their total amount. Disk-diffusion in agar showed an inhibition halo for P. aeruginosa in both films with more than 5.0% in ZnO-NP, whereas for S. aureus and S. Typhimurium, the inhibition zones were not detected after 48 h. In liquid tests, P. aeruginosa was the least sensitive microorganism: from 5 log CFU/mL, it reached 9 log CFU/mL in LLDPE-MA films without ZnO-NPs and 7 log CFU/mL in films with 5.5% of ZnO-NPs after 5 days. S. Typhimurium was the most sensitive in the liquid test, with 9 log CFU/mL growth in 5 days for films without ZnO-NPs and 3 log CFU/mL for 5.5% of ZnO-NPs, in 5 days. In conclusion, ZnO-NP incorporated on LLDPE-MA and LDPE films is a promising packaging technology to increase food shelf-life and safety.