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Applications of Cold Plasma Technology in Food

The Cold plasma is a novel nonthermal food processing technology that uses energetic, reactive gases to inactivate contaminating microbes on meats, poultry, fruits, and vegetables. This flexible sanitizing method uses electricity and a carrier gas, such as air, oxygen, nitrogen, or helium; antimicrobial chemical agents are not required. The primary modes of action are UV light and reactive chemical products of the cold plasma ionization process. A wide array of cold plasma systems that operate at atmospheric pressures or in low-pressure treatment chambers are under development. Reductions of greater than 5 logs can be obtained for pathogens such as SalmonellaEscherichia coli O157: H7, Listeria monocytogenes, and Staphylococcus aureus. Effective treatment times can range from 120 s to as little as 3 s, depending on the food treated and the processing conditions. Key limitations for cold plasma are the relatively early stage of technology development, the variety and complexity of the necessary equipment, and the largely unexplored impacts of cold plasma treatment on the sensory and nutritional qualities of treated foods. Also, the antimicrobial modes of action for various cold plasma systems vary depending on the type of cold plasma generated. Optimization and scale-up to commercial treatment levels require a more complete understanding of these chemical processes. Nevertheless, this area of technology shows promise and is the subject of active research to enhance efficacy.
Cold plasma (CP) is an emerging technology, which has attracted the attention of scientists globally. It was originally developed for ameliorating the printing and adhesion properties of polymers plus a variety of usage domains in electronics. In the last decade, its applications were extended into the food industry as a powerful tool for non-thermal processing, with diverse forms for utilization.
Cold plasma processing is an attractive technology for mild surface decontamination of foods and packaging materials. Wageningen Food & Biobased Research develops test units and proves that inactivation of micro-organisms is possible.
Cold plasma is otherwise referred to as the 4th state of matter. When you apply enough energy to a gas a plasma discharge can be achieved. It is estimated that 99% of the known universe is in a plasma state. The sun and stars are examples of natural plasmas. Man-made plasma can be generated at low temperatures typically by applying a voltage to a gas. The electric field generated from the applied voltage can accelerate any free electrons in the gas. Accelerated electrons collide with gas atoms to excite or ionize them. Ionization of gas atoms releases more electrons; this cascaded reaction can generate a rich abundance of highly reactive chemical species that are capable of inactivating a wide range of microorganisms including foodborne pathogens and spoilage organisms. The diffuse reactive species revert back to an inert gas atom once the applied voltage is removed.
The cold plasma technique uses cold gases to disinfect the surfaces of packaging or food products. The technique has the potential to inactivate micro-organisms on the surface of products and packaging materials at temperatures below 40 °C. Cold plasma is attracting a lot of attention from the food industry. Hardly a surprise, because many cleaning options are not heat-resistant, cleaning with water is expensive and chemicals are often out of the question. But gas reaches every nook and cranny.
 Nitrogen-based cold plasma
Many research groups that are active in the field of cold plasma for food applications use helium or argon as the carrier gas. Wageningen Food & Biobased Research uses nitrogen. Nitrogen-based gas plasma is virtually free of oxygen and thus ozone production – which is anticipated to have a negative impact on product quality parameters – is very limited. Nitrogen can be characterized as food-grade and is ubiquitously present in the air. Furthermore, active species have a relatively long lifetime of 1.6 seconds which results in a continuous afterglow of several meters in length. This has the advantage that the nitrogen-based gas plasma can be transported and therefore implementation in processing lines can be realized without large modifications of the existing infrastructure.

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