ZnO Nanostructures in Active Antibacterial Food Packaging: Preparation Methods, Antimicrobial Mechanisms, Safety Issues, Future Prospects, and Challenges

Packaging of food products is one of the most important stages of the food supply chain. Nano-size materials for packing food substances with appropriate properties result in better packaging performance and longer food shelf-life. In this review, the application of ZnO nano-size in active packaging of foods is discussed to identify gaps in applications for food packaging and safety. First, the crystal structures and morphologies of modified ZnO nanoparticles (ZnO NPs) are presented, and their synergistic effects on antimicrobial activities are discussed. This review also provides an overview of antimicrobial packaging containing ZnO NPs with a focus on preparation methods, antimicrobial mechanisms, and recent progress in packaging applications. The generation of reactive oxygen species (ROS) is the primary antimicrobial mechanism, which can be varied depending on morphology and size. Generally, ZnO NPs can inactivate fungi or Gram-positive and Gram-negative bacteria growth, which reduce the risk of cross-contamination, thereby extending the shelf life of products. Notably, the health concerns and hazards regarding the safety and migration of ZnO NPs application are also elaborated. Unintentional migration, inhalation, skin penetration, and ingestion may result in human health hazards. Therefore, to provide safety regulations, further investigations such as case by case study are recommended.