Because food contains large amounts of moisture, carbohydrates, and other substances, it is prone to spoilage under certain temperature and humidity conditions, which also provide a suitable medium and environment for microbial growth. Microbial contamination of food most often occurs during packaging, transportation, and storage. Plastic packaging has long dominated the market due to its advantages of being lightweight, easy to mold, and low-cost. However, traditional general-purpose plastics such as polyethylene and polypropylene suffer from poor antimicrobial properties, inadequate barrier performance, weak weather resistance, and difficulty in biodegrading. These shortcomings can easily lead to spoilage and waste of the contents, while also contributing to “white pollution.” According to industry statistics, product loss rates caused by microbial contamination and oxidative deterioration in food packaging exceed 15%, and traditional protective packaging cannot meet the long-term storage and transportation protection requirements of high-end products. The use of antimicrobial food packaging materials can help inhibit microbial contamination to a certain extent.
Ôxít kẽm is a typical multifunctional inorganic nanomaterial that combines structural reinforcement with multifunctional properties. It also exhibits excellent biocompatibility and is non-toxic to living organisms, meeting safety standards for food contact materials and pharmaceutical packaging. In recent years, by composite modification of zinc oxide nanoparticles with polymer matrices, it has been possible to simultaneously enhance the barrier properties, antimicrobial properties, and aging resistance of packaging materials.
Nano-zinc oxide possesses broad-spectrum antimicrobial activity and exhibits significant inhibitory and killing effects on common foodborne and environmental pathogens such as Escherichia coli, Staphylococcus aureus, and molds, making it the core functional component of active packaging. Its antimicrobial mechanism primarily involves three actions: First, the size effect of the nanoparticles allows them to penetrate microbial cell membranes, disrupting the integrity of the cell structure; second, under light or humid conditions, zinc oxide generates reactive oxygen species such as hydroxyl radicals and superoxide anions, which oxidize and break down microbial proteins and nucleic acids, thereby inhibiting bacterial reproduction; third, the slow-release of zinc ions interferes with microbial enzyme systems, blocking bacterial proliferation pathways. Compared to silver-based antimicrobial fillers, zinc oxide is lower in cost, does not lead to resistance, and withstands high-temperature processing, making it suitable for the high-temperature forming processes used in packaging films and coatings, while posing no safety or contamination risks to the contents.
The oxygen and water vapor barrier properties of packaging materials are key factors in determining the shelf life of the contents. Nano-zinc oxide particles can form a dense, mesh-like barrier structure within the polymer matrix, lengthening the diffusion path for gas molecules, significantly reducing the film’s gas and water vapor permeability coefficients, and effectively inhibiting the oxidation and moisture-induced deterioration of the contents. At the same time, zinc oxide possesses excellent UV-shielding properties, absorbing ultraviolet radiation in the 200–400 nm wavelength range. This blocks the photodegradation of polymer chains caused by UV radiation, significantly enhancing the packaging material’s weather resistance and anti-aging capabilities. It addresses the issues of brittleness caused by prolonged sun exposure and oxidation due to light penetration in traditional packaging, making it suitable for outdoor transportation and long-term storage scenarios.
Fresh fruits, vegetables, meat, and seafood are highly susceptible to spoilage caused by microbial growth and oxidation reactions; traditional passive packaging has a short shelf life and high wastage rates. Zinc oxide-modified active packaging achieves long-term freshness preservation through active antibacterial properties, oxygen and water vapor barriers, and UV shielding. Research data shows that blueberries packaged in zinc oxide-composite bio-packaging have a 29.1% longer shelf life, while microbial growth in pork and fresh meats is significantly reduced, effectively extending the shelf life of fresh products. At the same time, this type of packaging contains no chemical preservative residues, offering higher safety and meeting market demand for eco-friendly preservation of fresh foods.
With the continued growth in demand for smart and eco-friendly packaging, zinc oxide-modified functional packaging will continue to evolve and upgrade, driving innovation and development in the packaging industry.