Cold plasma devices developed to kill food pathogens

The devices could help processors meet stepped up regulatory standards on food safety. European consumers have become increasing concerned about food safety. As a result the EU and regulatory authorities in member states have been increasing their regulation of the industry, resulting in more costs and greater public scrutiny of manufacturers' operations. Recalls of products are also costly and impact on the company's brand image.

Cold plasma is a state of matter similar to a chemically and electrically reactive gas. Researchers involved in a University of Wisconsin project announced yesterday they used a cold plasma technique to develop the pathogen killing devices.

"Plasma species interact with inorganic and organic materials and change their structure,"​ stated Frank Denes, an associate professor of biological systems engineering at the College of Agricultural and Life Sciences.

In collaboration with Amy Wong, a microbiologist at the Food Research Institute, Denes said they have found that the plasma treatments reduce some bacteria populations by a factor of 1,000 to 100,000.

One device looks like a sandwich-sized block of white ceramic. One side features over 200 circles, arranged in a grid. Each circle houses an electrode, and when the reactor is on, they all work together to produce a constant and uniform flow of plasma. The reactor can be suspended, electrodes pointing downward, above any surface in need of disinfection, such as a moving conveyer belt.

The second device decontaminates water and other fluids. The device looks like a large glass jug that holds about 1 liter, fitted with specialized caps that house the electrical gadgetry needed to produce a plasma, a press release stated.

As liquids swirl inside the reactor, cold plasma inactivates the contaminants. Wong found that within 20 seconds, the reactor inactivates high concentrations of bacteria, killing up to 100,000 colony-forming units per milliliter of liquid.

Although cold plasma technology has been used for various manufacturing processes, Denes claims his invention is one of the first developed to work at atmospheric pressure.

Plasma is considered the fourth state of matter, along with the more familiar forms of solid, liquid and gas. A plasma is a gas with free electrons whizzing about. The electrons, accelerated by an electric or electromagnetic field, collide with gas atoms and molecules, fragmenting them to create reactive agents, such as ions, free radicals and other atomic particles.

According to estimates from the US Centers for Disease Control and Prevention, food-borne pathogens account for 76 million illnesses, 325,000 hospitalizations and 5,000 deaths in the country each year.