Naturally occurring germs are an important problem, especially in health care and food processing. To avoid health risks, medical devices, packaging but also food must be sterilized. Nowadays, this happens mainly through the use of high heat or chemicals e.g. hydrogen peroxide, ethylene oxide and peracetic acid. However, this is not always applicable to temperature or chemical sensitive materials such as plastics or food.
By using non-thermal "cold" plasmas, mild sterilization of even temperature-sensitive materials is possible. In non-thermal plasmas, the electrons are selectively heated, which then release their energy via excitation, ionization and dissociation to the gas, but without thermally heating it. The mechanism of the sterilization is then based on an interaction of the reactive species generated in the plasma, such as oxygen radicals and ozone, as well as the UV radiation, which damage the cell walls or the DNA material of the germs and thus kill the pathogens.
Various methods for plasma sterilization have been developed and investigated at IGVP. Microwave plasmas, arc discharges and dielectric barrier discharges (DBD) were used both in low pressure and at atmospheric pressure. The treated materials range from plastic surfaces to cellulose fabrics and wine corks to peppercorns and spice powders. The plasma processes showed a high disinfection effect with a germ reduction of more than 4 orders of magnitude in the second to minute range for spores such as Bacillus subtilis, Aspergillus niger or Geobacillus stearothermophilus.
Stefan Merli
Dr.Research associate, Plasma Technology
Andreas Schulz
Dr.-Ing.Research associate, Plasma Technology