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Cold plasma for food application

Identification

Key words atmospheric pressure plasma, cold pasteurisation, low-pressure plasma, microwave plasma, glow discharge plasma, decontamination, sterilization
Latest version 2011/05/18
Completed by IRTA

How does it work?

Primary objective Decontamination/ sterilisation of food products surface
Working principle Gas plasma is a neutral ionized gas containing on the one hand, charged particles, free electrons and ions, and on the other hand neutral reactive species such as atoms and molecules. When such ionized gas is submitted to an electric field, charged particles are accelerated producing collisions with the atoms and molecules. Consequences of these collisions are new charged particles (ions, electrons and free radicals), chemical reaction with sample surface and creation of photons in the UV range.

UV radiation and collision with heavy ions have a strong effect on the survival of biological species (bacteria, virus…), creating important structural damage on the cell membrane. Because sample temperature remains mostly unchanged during processing, the technology is considered to be a non-thermal one.

For food application there are two general principles:

1. The low-pressure plasma (Fig. 1) consists of creating a vacuum inside a cavity (called plasma reactor) and filling it partially (vacuum remains at 0.01 – 0.02 MPa in the plasma reactor) with a gas such as argon, N2O, N2 or oxygen. Plasma can be generated by a radiofrequency field (typically of 13,6 MHz) between two electrodes or by microwave energy (typically 2450 MHz) from an antenna or emitter.

2. The atmospheric plasma (Fig. 2) consists of creating a plasma at ambient pressure (0.1 MPa) using a high potential difference between two electrodes placed in a gas mixture. There are different ways to generate atmospheric plasma such as Radiofrequency plasma (RF plasma), corona discharge plasma, resistive barrier discharge (RBD) plasma and gliding arc discharge plasma. For food application the RBD discharges and One atmosphere uniform glow discharge plasma (OAUGDP) system look promising. In the first one, a high-resistivity material is inserted in the discharge gap between a high voltage electrode (HV Electrode) and a low voltage electrode (Ground Electrode) connected to a transformer. The barrier limits the discharge current thus preventing uncontrolled arcing generation. For the second one a gas mixture (argon or CF4) is blown between the two electrodes where a high potential difference is applied creating a stable glow discharge and thus the plasma.

2 1 1 cold plasma 2.JPG

Fig. 1: Low-pressure plasma sketch; © Pierre Picouet

2 1 1 cold plasma 1.JPG

Fig. 2: Atmospheric plasma (RBD discharges) sketch; © Pierre Picouet

Images
Additional effects
  • Decontamination effect on Listeria monocytogenes in cheese and cooked ham or Salmonella on the surface shell eggs.
  • Reactive oxygen species (ozone, oxidation of amino acids and nucleic acids, lipid oxidation) might occur during processing, especially for the atmosphere pressure system.
  • Oxidation of vitamins C and E., lipids or other sensitive food ingredients.
  • Uniform and nanometric coating of plastics for the food sector using a low-pressure plasma system.
Important process parameters gas mixture, pulse voltage, pulse duration, pulse repetition rates, pressure, distance between electrodes
Important product parameters size, geometry, surface shape

What can it be used for?

Products Cooked ham, cheese, legumes, dry fruits, eggs & plastics (PP, PE & PET).
Operations In the low-pressure plasma technology, chambers of up to 12.000 liters can be used with a vacuum mechanism to replace the air by a noble gas; even if it is a batch technology, short cycle plasmas system can be inserted in an automatic process line.

In the atmospheric plasma, distance between electrodes (maximum 8 cm) and treatment time are critical parameters as well as the surface area; samples can be situated on a conveyor belt for a continuous processing.

Solutions for short comings For some industrial processes it is important to have a pre-treatment of the products or packaging surface. Cold plasma, as well as light pulse of UV, can be a simple and cost benefit technology to fulfil this goal.

What can it NOT be used for?

Products Foodstuff with high lipid content and/or high vitamin content.
Operations It is a surface decontamination on the first millimetres; the centre of the product is not affected.
Other limitations Unwanted burns might occur just below the surface and damage the texture of the food products.
Risks or hazards Depending on the gas mixture, the one atmosphere uniform glow discharge plasma system can generate a high amount of ozone.

Implementation

Maturity The technology using vacuum pumps exists for industrial applications other than food industry. The RF-Plasma have been proven on a small industrial scale, the OAUGDP exists at small scale for pilot plant applications.
Modularity /Implementation The modularity will depend on the application and the chosen technology (atmospheric plasma, nitrogen plasma…).
Consumer aspects Up to now there is no information on consumer acceptance of this technology.
Legal aspects The system can generate UV photons and ozone gas, thus the local legislation on UV and ozone must be applied.
Environmental aspects No information is available, but the environmental impact might be associated with high voltage and ozone generation.

Further Information

Institutes Wageningen UR - FBR, CRIC
Companies Diener, OMVE Netherlands
References 1. Basaran P., Basaran-Akgul N. & Lutfi Oksuz L. (2008). Elimination of Aspergillus parasiticus from nut surface with low pressure cold plasma (LPCP) treatment. Food Microbiology 25, 626–632

2. Critzer F.J., Kelly-Winterberg K., South S.L. & Golden D.A. (2007). Atmospheric Plasma Inactivation of Foodborne Pathogens on Fresh Produce Surfaces. Journal of Food Protection, Vol. 70(10), 2290–2296

3. Fernandez A., Shearer N., Wilson D. R.& Thompson A. (2011). Effect of microbial loading on the efficiency of cold atmospheric gas plasma inactivation of Salmonella enterica serovar Typhimurium. International Journal of Food Microbiology. 152(3):175-180

4. Laroussi M. (2002). Nonthermal Decontamination of Biological Media by Atmospheric-Pressure Plasmas: A Review, Analysis and Prospects. IEEE Transactions on Plasma Science Vol. 30, 1409-1415

5. Laroussi M., Mendis D.A. & Rosenberg M. (2003). Plasma interaction with microbes. New Journal of Physics Vol. 5, 41.1–41.10

6. Mastwijk H.C. & Nierop Groot, M.N. (2010). Cold Plasmas used for Food Processing, Encyclopedia of Biotechnology in Agriculture and Food 1: 1, 174 — 177

7. Moisan M., Barbeau J., Moreau S., Pelletier J., abrizian M. & Yahia L’H. (2001). Low-temperature sterilization using gas plasmas: a review of the experiments and an analysis of the inactivation mechanisms. International Journal of Pharmaceutics 226, 1–21

8. Moreau M., Orange N. & Feuilloley M.G.J. (2008). Non-thermal plasma technologies: New tools for bio-decontamination. Biotechnology Advances 26, 610–617

9. Ragni L., Berardinelli A., Vannini L., Montanari C., Sirri F., Guerzoni M.E.& Adriano Guarnieri A. (2010). Non-thermal atmospheric gas plasma device for surface decontamination of shell eggs. Journal of Food Engineering 100, 125–132

gas mixture, pulse voltage, pulse duration, pulse repetition rates, pressure, distance between electrodes size, geometry, surface shape Plasma equipment 2.1.1 physical, chemical stabilizing, packaging, other biotechnology, nanotechnology, other Internal Data base, Web of Knowledge, Scopus, companies websites Search terms: atmospheric pressure plasma, cold pasteurisation, low-pressure plasma, microwave plasma, glow discharge plasma, decontamination, sterilization, combined with food, meat and fruits WikiSysop :Template:Review document :Template:Review status



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Created by Hte irta on 9 February 2012, at 11:03