## 1 Introduction  
During the last decade, consumers have been seeking more nutritious, less chemically processed foods. They are expecting \"bacteria-free\" products with high quality and long shelf life. These rather contradictory demands lead to a new interdisciplinary field of study that combines physics, biology and chemistry in food safety investigations, focused on guaranteeing and improving nutritional qualities. That is why plasma technologies and their applications in the food industry have become one of the newest trends in scientific research. The number of interdisciplinary scientific papers focused on cold atmospheric plasma (CAP) sources for food treatment and sterilization has increased significantly, mainly in the last decade [1; 2; 3; 4; 5; 6]. The plasma applied for the food exposure must be a non-equilibrium one with a gas temperature around 20-50 \({}^{\circ}\)C to avoid the degradation of vitamins, proteins and other biological and biologically active compounds. On the other hand, the treating gas must be well activated, i.e., it must contain a high concentration of agents initiating bacterial inactivation. These conditions can be very effectively fulfilled by Atmospheric Pressure Non-Thermal Plasmas (APNTPs), where the neutral gas temperature (i.e., the temperature related to the kinetic motion of heavy particles--atoms, molecules and ions) remains close to the ambient one but the free-electrons temperature typically reaches thousands of Kelvin. Thus, APNTPs generate ionized gases at conditions far from the thermodynamic equilibrium. Using common gases such as air or argon, one can produce reactive oxygen and nitrogen species (ROS and RNS) [7; 8] as well as ozone [9], oxides, peroxides and monoxides [10], even in a short treatment time of a few seconds. Additionally, the electrical discharge plasmas also produce effectively ultraviolet (UV) radiation in UVC range and vacuum ultraviolet radiation (VUV) that have strong bactericidal effects [11; 12; 13]. Such devices [14] could be built on the base of the corona discharge [15], the dielectric barrier discharge [16], the glow discharge [17], the plasma jet or the nanosecond pulsed discharge [18]. To achieve good bactericidal results without any harm to the food quality during the non-equilibrium plasma treatment requires low power, low temperature and short treatment times. Additionally, the technological simplicity and robustness (including a long operation lifetime without any service) of devices are required.  
There is plenty of evidence for the potential of CAP in spoilage prevention of various food products and extension of their fresh state. Recent studies showed that cold plasma is efficient in the inhibition of food-borne bacteria such as _Escherichia coli_[19], _Salmonella typhimurium_[20], _Staphylococcus aureus_[21] and _Listeria monocytogenes_[22]. It is also effective against yeasts and molds [23]. Although the detailed mechanisms of cold plasma interaction with food are still not fully understood [24], the cold plasma (DBD, plasma jet) effect has been studied in surface decontamination of perishable fruits such as strawberries [25; 26], blueberries [27; 28] or food model systems [29].  
The aim of this paper is the investigation of how a surface wave sustained plasma torch operating in argon at a 2.45 GHz wave frequency [30] interacts with strawberries, cherries and blueberries. Resistance of a fruit-borne population of microorganisms after the plasma treatment at various conditions is studied. Optical emission spectroscopy is used for reactive species determination. Thermal imaging during the treatment gives information about the fruit surface temperature. The effect of CAP on the antioxidant properties of the treated fruits is examined, too.