Cold Plasma Technology is a modern and eco-friendly process with a wide range of potential applications in food packaging. Initially developed to enhance the surface energy of polymers, improving adhesion and printability, it has recently gained popularity as a powerful tool for surface decontamination of food and food packaging materials. There is a growing trend in developing in-package decontamination, providing a non-thermal treatment of foods after packaging. This technology works by generating a low-temperature plasma containing highly reactive species, such as ions, radicals and UV photons, which can modify the surface properties of polymers, such ashydrophilicity, surface energy and surface roughness, resulting in improved barrier properties and reduced permeability to gases and liquids. These modifications also contribute to the anti-bacterial and anti-fungal properties of the packaging material, thus extending the shelf life of the food product. Cold plasma technology is a versatile process that can be applied to a wide range of food packaging materials, including plastic films, coatings and laminates, without altering the bulk properties of the material. It is a promising technology for improving the safety and quality of food products, reducing food waste and promoting sustainable packaging practices in the food industry.
Cold Plasma Technology induces a range of physical and chemical processes both within the plasma volume and on the plasma-polymer interface, leading to modifications in the surface properties of packaging polymers. These modifications can be used for surface functionalization, providing selective and adjustable surface energies to promote adhesion or anti-adhesion, improving printability and sealability, imparting anti-mist properties and enhancing the polymer’s resistance to mechanical failure. Plasma deposition of barrier layers can also improve the barrier properties of packaging materials towards gases, such as oxygen and carbon dioxide as well as chemical solvents.
Furthermore, gas plasma reactions can effectively inactivate microorganisms, such as bacterial cells, spores, yeasts and moulds adhering to polymer surfaces within short treatment times. This technology offers a rapid and efficient method for sterilizing packaging materials, like plastic bottles, lids and films without adversely affecting their bulk properties or leaving any residues. This makes cold plasma technology an excellent choice for enhancing the safety and shelf-life of food products by reducing the risk of contamination and spoilage as well as reducing food waste.
The mechanism involved in microorganism inactivation during plasma treatment is complex and involves several processes. The radicals present in the plasma bombard the surface of the microorganisms with high intensity, leading to the formation of lesions that the microorganisms cannot repair quickly. This process is known as “etching,” and it destroys the living cells rapidly. The accumulation of electrostatic forces on the exterior surface of the living cells is responsible for the phenomenon of lesion formation.
The efficiency of non-thermal plasma depends on two factors: the substrate type and the characteristics of the microorganisms, such as load, type and physiological state. The action of charged particles and reactive species in non-thermal plasma damages the cell membrane and causes denaturation of DNA and chemical bonds, resulting in an antimicrobial effect on the cell.
The interaction between microorganisms and species present in plasma is not yet fully understood. However, it is believed that certain reactions, such as oxidation and peroxidation occur both inside and outside the cell, catalyzed mainly by the plasma ions.
Overall, the mechanism of microorganism inactivation during plasma treatment involves a complex interplay between various physical and chemical processes and the efficacy of the treatment depends on several factors. However, cold plasma technology offers a promising solution for the rapid and efficient sterilization of packaging materials and food products without adversely affecting their bulk properties or leaving any residues, making it a valuable tool for the food industry.
Cold plasma is an emerging technology that offers unique benefits such as treatment at low or ambient temperature for short periods of time and retaining food quality and integrity. It efficiently sanitizes equipment, inactivates food-borne pathogens in fresh produce and packaging, catalyzes certain manufacturing processes, acts as active packaging and retards browning in fruits and vegetables. It is effective in retaining the texture, sensory and functional properties of foods, making it a promising technique for food processing in the future.
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