ABSTRACT

For the food industry, it is important to produce reliable products that are free of hazards and preserve them for long periods. Many microorganisms can grow in food without causing any changes in physical properties like odor, color, texture of food, while simultaneously producing metabolites that threaten human health causing illness and even deaths, damaging the national and global economy (Pawłowski 2015, Piecuch & Hewelt 2013, Piecuch & Piecuch 2013). Sterilization is a physical or chemical process that eliminates or kills all forms of life, especially microorganisms present on a surface or contained in a fluid such as biological culture media (Moisan et al. 2002). It is a key process for food processing. Harmful microorganisms can cause detrimental effects such as rotting or disease, consequently leading to economic losses. Inactivation of these microorganisms can be accomplished by conventional techniques such as heat, steam, chemical solutions or gases, radiation, as well as the recently developed techniques. However, most of these sterilization methods can cause damages to the material or limit complete sterilization (Park et al. 2007a). This opens new research areas for development of alternative sterilization methods (Lee et al. 2006). Plasma sterilization is considered to be a promising alternative to the conventional sterilization methods. It is a versatile, fast

Food materials contain various nutritive compounds such as vitamins, polyphenols etc. These compounds are very sensitive especially to heat. Plasma contains a wide variety of active particles, such as electrons, ions, radicals, metastable excited species, and ultraviolet radiation that has sufficient energy to break covalent bonds and initiate certain reactions and form volatile compounds (Sen et al. 2012). All these active species and heat lead to the death of cells. In addition to this, they can affect the nutritive compounds found in the food products. In the present study, the DBD (Dielectric Barrier Discharge) non-equilibrium plasma jet source has been applied to check the applicability of the plasma sterilization method without causing appreciable changes on vitamin C (L-ascorbic acid) content of food. In a non-equilibrium plasma the electron energies are much larger than the energy of other particles (ions and neutral particles), whereby it is possible to carry out a biochemical and physical reaction at a relatively low temperature of the working gas. Due to the selectivity of energy and the possibility of adjusting parameters of the plasma over a wide range, it has found many applications in environmental engineering, food industry and medicine (Weltmann et al. 2010, Pawłat et al. 2011, Stryczewska et al. 2013, Pawłat 2013, Raniszewski 2013, Hensel et al. 2015, Brisset & Pawłat 2016). Nozzle-shape plasma jet reactors can be used for these applications (Weltmann et al. 2010, Pawłat 2013, Pawłat et al. 2013, Kwiatkowski et al. 2014, Pawłat et al. 2015, Zaplotnik et al. 2015). The plasma generated inside such reactor is transported outside of the nozzle under forced gas flow. In the present study, the DBD reactor with two ring electrodes was used (Fig. 1).