Cold Atmospheric Plasma

Cold plasma is a non-thermal technology which can be used for the inactivation of microorganisms.



Coming from the medicine and textile industry sector and being known for its excellent antimicrobial properties, plasma has also entered the world of food science and technology.

Plasma can be described as the "fourth state of matter", generated by applying energy in the form of heat, voltage, irradiation or electromagnetic fields to a gas, leading to reactions like ionisation, excitation and dissociation. As a consequence, various active components such as radicals, UV radiation and charged particles are being formed.

Depending on the source of energy and the pressure, the resulting plasma can be thermal or non-thermal. Thermal plasmas can be used for instance for the modification of product surfaces (e.g. etching) whereas non-thermal or "cold" plasmas can be used for the decontamination of heat sensitive products like catheters. Currently much effort is put into plasma research to answer the question, if plasma could also be used as a "gentle" technique for the treatment of foodstuff.

There are basically two major fields of interest in the food area: the inactivation of microorganisms and enzymes and the improvement of food packagings. Since traditional food preservation methods like thermal processes go hand in hand with losses in nutritional and sensorial quality, cold plasma could be a gentle alternative. First studies have confirmed its good antimicrobial properties and their ability to inactivate undesired enzymes, leading to enhanced food quality characteristics. Great development has taken place in the field of food packaging. Today it is possible to improve the impermeability of PET bottles regarding O2 and CO2 (40-fold) by coating the inner surface with an amorphous carbonate layer, using a special low pressure plasma and acetylene as process gas.



Figure: Cold atmospheric plasma on fresh lamb's lettuce (© by Matthias Baier, ATB Potsdam, Germany)






This text was prepared by Bjoern Surowsky, Berlin Institute of Technology (Technische Universität Berlin), Department of Food Biotechnology and Food Process Engineering, Berlin, Germany.

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