Long- and short-term antibacterial properties of low-density polyethylene-based films coated with zinc oxide nanoparticles for potential use in food packaging

Abstract

Concerns in food safety and the need for high-quality foods have increased the demand for extending the shelf life of packaged foods. Subsequently, promoting and investigating the development of antibacterial materials for food packaging has become inevitable. Zinc oxide nanoparticles have attracted attention lately owing to their multifunctional properties, especially antibacterial activity. For this study, antibacterial low-density polyethylene films were prepared by coating zinc oxide nanoparticles onto their surface. The low-density polyethylene film antibacterial activity was evaluated toward Gram-positive and Gram-negative bacteria. The scanning electron microscopy images showed that using anhydride-modified low-density polyethylene (LDPE-g-AM) resin permitted improved zinc oxide nanoparticle distribution on the low-density polyethylene film surface, reduced the agglomerate sizes, and reinforced the zinc oxide nanoparticle bonding to the low-density polyethylene film surface. We found that the coated low-density polyethylene films exhibited high antibacterial activity against both strains. The antibacterial tests also proved that the coated films retained their antibacterial efficiency toward Escherichia coli, even after eight months, with a reduction rate higher than 99.9%, whereas for Staphylococcus aureus the antibacterial properties for the linear low-density polyethylene (LLDPE) films decreased at eight months and improved for the LDPE-g-AM films. When the zinc oxide coated films were laminated with neat low-density polyethylene, only the LDPE-g-AM was still active against E. coli provided that the lamination thickness does not go beyond 8 µm. This research demonstrated that the coated low-density polyethylene films have excellent attributes when used as an active coating in the food packaging industry.