Cold plasma processing for food safety

 Cold plasma is an emerging food processing technology which has been shown to effectively inactivate pathogenic bacteria, viruses, parasites, and fungi. The process uses high-voltage electricity to ionize air and/or defined gas blends to create a mixture of ions, free electrons, ozone, radical species, and other reactive products. This energetic plasma, which operates near room temperature, has been tested with fruits, vegetables, nuts, meats, cheeses, poultry, seeds, powders, and other foods. 

 Once created at the high voltage electrodes, the cold plasma is applied to foods and food contact surfaces. Forced air can blow the cold plasma over products and surfaces, as with plasma jet systems. This allows for the varying treatment distances of irregularly shaped foods. The commodity may also be moved in and out of the plasma field, as with dielectric barrier (DBD) systems. In either case, reactive chemical species in the cold plasma break the cellular structures, DNA, and proteins of pathogens on foods, inactivating them. Efficacy is dependent on treatment intensity and duration. Combining cold plasma with chemical sanitizers, high intensity light, or other food safety interventions can provide enhanced, synergistic pathogen inactivation. Short treatments with cold plasma can induce sublethal injury in pathogens, rendering them more susceptible to another sanitizing processes.

Some forms of cold plasma are completely waterless, using only use air and electricity. These are suitable for dry environments and low-moisture foods. In other systems, water is used as a medium for the cold plasma reactive chemical species, delivering them onto the surfaces of foods and food contact surfaces. This plasma activated water (PAW) is effectively a sanitizing solution, generated on-site and on-demand, without chlorine-based sanitizer precursors or organic acids. Because it uses only air, electricity, and water, cold plasma is a green sanitizing process. In research, some forms of the equipment have been made compact enough for field use and in point-of-service applications.

Cold plasma has shown antimicrobial efficacy against Salmonella, Escherichia coli O157:H7, Listeria monocytogenes, norovirus, Crypotosporidium, and other foodborne pathogens. The rapidly growing body of research has examined a wide range of food commodities, food contact surfaces, packaging materials, and other applications important to food safety professionals and the food industry. Like all new food processing technologies, cold plasma requires a thorough review by the controlling regulatory authorities for each commodity and within each jurisdiction, national and international. As of this writing, regulators in the US, EU, Asia, and Africa are actively reviewing the research developments related to cold plasma but have not yet issued approvals for it to be used as a food safety process.

 Research into cold plasma, as a stand-alone treatment or in combination with other sanitizing processes, is one of the most significant areas of inquiry for nonthermal food processing in recent years. As an efficient, green antimicrobial process, cold plasma has been shown to be flexibility and amenable for scale up to commercial trials and implementation. 

Further Reading:

Bermudez-Aguirre, D. 2020. “Advances in Cold Plasma Applications for Food Safety and Preservation.” Elsevier Inc, London, UK.

Cullen P.J., et al., 2018. “Translation of plasma technology from the lab to the food industry.” Plasma Processes and Polymers. 15(2):1700085

Hori M. and Niemira B.A. 2017. “Plasma Agriculture and Innovative Food Cycles.” J Phys D: Appl Phys 50 323001:20-21

Niemira, B.A. 2021. “Plasma decontamination of plant related food products.” In “Innovative Food Processing Technologies: A Comprehensive Review” K. Muthukumarappan and K Knoerzer (eds), Elsevier Inc, London, UK

Özdemir, E., et al. 2023. “Cold plasma application to fresh green leafy vegetables: Impact on microbiology and product quality”. CRFSFS, DOI: 10.1111/1541-4337.13231

Sarangapani C., et al. 2018. “Recent Advances in the Application of Cold Plasma Technology in Foods.” Annu Rev Food Sci Technol 9:609–29

About the author: Brendan A. Niemira, Ph.D. is with the U.S. Department of Agriculture, Eastern Regional Research Center in Wyndmoor, PA.