# Quality of Tomato Juice as Influenced by Non-Thermal Air Plasma Treatment
## 3 Results and Discussion
### Effect of CAP on Microorganisms Eradication  
The presence of microorganisms in the unpasteurized tomato juice is responsible for its spoilage and, after several days of storage, makes it unsuitable for consumption. The lower the initial total number of microorganisms in the juice, the longer its shelf life. The initial total number of microorganisms in freshly prepared tomato juice depends on the quality of the vegetables used and the hygienic conditions of the juicing process. In the following days of refrigerated storage, the number of microorganisms increases due to their proliferation, which leads to juice spoilage and makes it endanger health in case of consumption. The total number of aerobic mesophilic microorganisms in edible juice should not exceed 3-4 log\({}_{10}\) CFU/mL (Codex standards, 2005). It is assumed that the colony counts exceeding 4 log\({}_{10}\) CFU/mL are responsible for the spoilage of the juice. In the present study, tomatoes were washed under warm running water before being used for juicing but were not sterilized. Likewise, the juicer was washed with washing-up liquid, without any germicides. The results showed that after just one day of juice storage under refrigeration conditions, the average number of mesophilic aerobic microorganisms in the tested samples was 3.22 log\({}_{10}\) CFU/mL. With such a total number of microorganisms, the juice showed no signs of spoilage and was safe for consumption. After 3 days of refrigerated storage, a minor increase in the number of colonies formed by aerobic microorganisms (3.40 log\({}_{10}\) CFU/mL) was observed, however, after 5 days of storage, their number increased to a high level exceeding 5 log\({}_{10}\) CFU/mL, and after 10 days it was greater than 6 log\({}_{10}\) CFU/mL. From the fifth day, a change in the organoleptic features of the juice was noted, and after 10 days, clear signs of deterioration were visible, including mold development on the surface of the juice. The content of yeast and mold after 1 day of storage was at a very low level (less than 0.5 log\({}_{10}\) CFU/mL); however, their intensive proliferation during storage was noted, largely contributing to juice spoilage. After only 3 days their number increased to a level close to 3 log\({}_{10}\) CFU/mL, and after 10 days it reached the value of 3.66 log\({}_{10}\) CFU/mL. The results showed that, despite the low pH and low sugar content of tomato juice, the total number of aerobic microorganisms increased during refrigerated storage and after about 5 days made it unfit for consumption. The effectiveness of the treatment of freshly prepared juice samples with CAP in elimination of the total number of mesophilic aerobic microorganisms depended on the time of this treatment. The 30 s CAP treatment did not produce the desired effects as a reduction in the total number of microorganisms by less than 1 log\({}_{10}\) CFU/mL was achieved, and after 10 days of storage there was a reduction of about 2 log\({}_{10}\) CFU/mL in comparison to the untreated control (Figure 2). Similarly, the treatment with CAP for 60 and 120 sec had little effect of reducing the number of colonies counted after 1 and 3 days of storage, but the microorganisms in these samples proliferated much slower than in the control Thus, after 5 and 10 days of storage a reduction in the number of microorganisms by more than 2 log\({}_{10}\) CFU/mL was observed compared to the control sample. The treatment with CAP for 300 s was found to be much more effective, the number of colony-forming units was reduced to an average of 1.83 log\({}_{10}\) CFU/mL and during the following days of storage it was kept at a low level of just over 2 log\({}_{10}\) CFU/mL, making the juice suitable for consumption even after 10 days of refrigerated storage. The greatest efficiency in erasing the microbial content was obtained by plasma treatment of the juice samples for 600 s. In this case, the number of colony-forming units dropped to less than 0.5 log\({}_{10}\) CFU/mL and did not increase during the 10 days of storage (Figure 2).