## 3 Results
### Plasma Inactivation of Microorganisms at Fruit Surface  
The results of the weighted average number of the total colony-forming microorganism units (no microorganism specified) are presented in Figure 7. There is no significant variation in the number of colony-forming microorganism units between the groups for strawberries, as is shown in Figure 7 on the left. This means that no bacteria inactivation is achieved. Figure 6: Intensity profiles of the selected active species along the plasma torch during the fruit treatment. Zero position is the end of the quartz capillary, the fruit surface was positioned at 9 mm (the tip of the plasma torch). MW power of 9 W, the argon flow of 7 L/min and the cooling air flow of 4 L/min were maintained in all cases. In contrast to strawberries, for both cherries (Figure 7, middle) and blueberries (Figure 7, right) a decrease in the number of colonies is observed. For cherries, the treatment duration of 15 s has a negligible effect, but a longer treatment of 30 or 60 s has a positive effect, as shown in Figure 7 (middle). The most pronounced antimicrobial effect of the plasma torch treatment is detected for blueberries, where 30 and 60 s treatment durations cause a reduction in the CFU number (Figure 7, right). The inhibiting impact of the plasma torch is determined by the surface characteristics of the tested fruits and the kind of microbial contamination. Strawberries often grow in contact with the soil microbiota and their rough surface covered with seeds would requires prolonged plasma exposure. In contrast, smooth fruits as cherries and blueberries would be easier to disinfect. Bearing in mind the smaller size of the blueberries, one can assume that the most pronounced antimicrobial effect obtained after their treatment is due to the larger relative surface area in contact with the plasma jet. Because of the higher temperature of the blueberries' surface, one can assume that thermal effects play an important role in this case. Comparing the results in Figure 7 with those in Figure 6, one can assume that there is a correlation between the NO intensity (i.e., the NO density) and a decrease in the number of colonies in the different types of fruits. The NO intensity strongly increases close to the plasma torch end where the cherries and blueberries are. The NO intensity at this axial position is lower when the strawberries are treated and there is no effect on the microorganisms in this case. Similar behavior, but with less significant a difference for the strawberries, can also be seen for the OH intensity. The obtained results suggest the need for specific CAP adjustment for the treatment conditions depending on the particular object. Optimization of the gas discharge conditions may result in a change in the total number of vital microorganisms (i.e., microorganisms able to replicate). Results for blueberries treated at different discharge power are presented in Figure 8.  
The most investigated variation of the treatment conditions is directed to decrease the average number of CFU per group compared to the control group. The results obtained show two interesting features that are in contradiction with the expectations and results obtained for other plasma sources. Figure 8: Average number of colony-forming units for blueberries after treatment at: 5 W (**left**); 7 W (**middle**), and 9 W (**right**) applied power for: control group and treatment times of 15, 30, and 60 s. The fruit was positioned at the torch tip at all powers. The argon flow of 7 L/min and the cooling air flow of 4 L/min were fixed in all cases. Figure 7: Average number of colony-forming units of microorganisms for strawberries (**left**), cherries (**middle**), and blueberries (**right**) exposed to plasma for different treatment time and after incubation of 72 h. Treatment was realized at the plasma torch tip at MW power of 9 W, argon flow of 7 L/min and cooling air flow of 4 L/min. The better results in microorganism deactivation are obtained at lower wave power (5 W, Figure 8 left).