Cold Plasma Technology Will Benefit The Food-Processing Industry

By Sam Lewis

This new technology may prove to be the most-effective means of microbial intervention in food while also being a money and time-saving phenomenon

Meat and poultry contributes to approximately 22 percent of the estimated 9.6 million foodborne illnesses occurring each year. As consumers demand higher-quality, more-nutritious foods, they also look for less processing combined with a longer shelf life. The food-processing industry has made great strides toward this and has also put in place numerous intervention technologies designed to ensure a more-sanitary manufacturing environment. The industry currently uses some novel processing methods for the decontamination of food and food contact surfaces. X-Ray, pulsed light, ultraviolet (UV) light, e-beam, and high-pressure processing (HPP) are just some of the technologies gaining in popularity in meat-processing plants.

The newest, and by far the most unique, technology is Atmospheric Cold Plasma (ACP).  Tests so far demonstrate its promise as a cost-effective means by which to extend the shelf-life of numerous produce and meat products, as well as effectively reducing foodborne pathogens. The Journal of Bioscience and Bioengineering published an article on In-package atmospheric pressure cold plasma treatment of cherry tomatoes.  The results of the research suggest that cold plasma could be used to decontaminate cherry tomatoes without compromising the quality of the product. The Society for Applied Microbiology published results demonstrating the efficacy of dielectric barrier discharge atmospheric cold plasma (DBD-ACP).  In these tests, DBD-ACP effectively inactivated high concentrations of liquid-suspended E. coli within sealed packages.

ACP has its origins in the physics of the universe. Considered the fourth state of matter — following solid, liquid, and gas — plasmas are created by applying power, in the form of heat, current, or light, to a gas. This application breaks down the gas molecules into ions, free electrons, and reactive metastable species. Cold plasmas have been proven to inactivate bacterium, spores, and fungi in food products. The concentrations of cold plasmas are controllable, depending upon how the plasma is generated. The lifetime of these reactive gases can also vary from a microsecond to hours, largely dependent upon the environmental conditions.

Unlike ozone generation systems, which can result in degradation of food, other reactive gases are being explored with less-oxidative effects. The majority of studies have been focused on fruits and vegetables due to high incidents of foodborne-pathogen contamination, with excellent results. The testing is now expanding to include the treatment of food-processing equipment, as well as meat and poultry products. Researchers are hoping to optimize the effects while reducing treatment times. So far results have been very positive against aerobic organisms, Listeria, S. aureus, S. Typhimurium, S. enteritidis, and Pseudomonas fluorescens on products, processing equipment, and packaging.  

Experts believe the advantages of ACP are:

• ACP requires short process times
• ACP is readily adaptable to a number of food-processing environments
• ACP is a dry process, requiring very small amounts of energy
• The reactive gases revert back to the original gas within a relatively short amount of time

Because this is a new, emerging technology, regulatory review and approval will be required. Ozone generation technology is already Generally Recognized as Safe (GRAS) for food. However, if the ACP devices prove to be significantly different, the approval process could be time-consuming. At the very least, it is expected the Environmental Protection Agency (EPA) and the Occupational Safety Health Administration (OSHA) may need to weigh in. The Federal Food, Drug, and Cosmetic Act (FFDCA) may require a process filing, while the FDA will determine if a chemical residue resulting from the process will require an indirect food additives petition. These are just a few of the considerations that will go into determining the ability to utilize ACP technology going forward.

At least one expert, Kevin Keener, believes the process will not prove to leave chemical residues. He expects that ACP will be deemed “clean” and “natural,” an organic process and an improvement over currently available antimicrobial procedures. Keener is a Distinguished Fulbright Professor of Food Science and Food Process Engineering and the Director of the Food Technology Development Laboratory at Purdue University.