## 3 Results and Discussion
The reduction in the number of bacteria and fungi was at a high level of R = 85-100% (Figure 4). A statistically significant difference was found in the level of reduction in microorganisms (bacteria and fungi) between the third minute of the process and the next minutes of the ozonation process for all tested systems (Table S3). After 5 min of ozonation, bacteria and fungi were almost completely eliminated from the parsley. Moreover, it is worth noting that with a larger batch of plants (75 g parsley), the decontamination process should be extended to 5 min to achieve the same effect as with a smaller mass of plants. In this case, significant statistical differences were found in the fifth minute of ozonation compared to the previous time (Table S3). It is noteworthy that there was a lack of change in the number of microorganisms in the sample rinsed with tap water. Only after 10 min were about 23% of the microorganisms removed, and after 15 min of rinsing, the number of microorganisms decreased by 30% (Figure 4). Therefore, rinsing parsley leaves in ozonated water with an ozone concentration of 1.5 mg/L in a closed circuit for 5 min can be recommended for industrial processes. The effects of treatment by washing with distilled, ozonated, and chlorinated water on the numbers of _Escherichia coli_ and _Listerina innocua_ bacteria on fresh parsley leaves have recently been studied by [PERSON] and [PERSON] [44]. It was shown that microbial reduction with ozonation was approximately 1 log higher than the reduction obtained with chlorine. The same authors report that chlorine was more effective against _E. coli_ than ozone (3.2 and 2.2 log reductions, respectively). There was no significant difference in _L. innocua_ counts obtained with chlorine and ozone. In our study, the level of reduction was much higher, which resulted from the optimization of the dose and time of ozonation. The effects of ozone and salicylic acid on the post-harvest quality of parsley bunches during storage have been studied by [PERSON] and [PERSON] [64]. The authors used gaseous ozone at a dose of 2.14 mg/m\({}^{3}\). After the process, the parsley batches were stored at 1 \({}^{\circ}\)C and 90% (\(\pm\)5%) relative humidity for 28 days. Salicylic acid was found to be a better way of retaining the sensory quality of the parsley, whereas ozone had a negative effect on appearance and taste. During storage after ozonation, the rate of respiration and ethylene production (indicators of metabolic activity) were suppressed in parsley treated with ozone gas. This indicates the inhibition of metabolic processes after ozonation using gaseous ozone. Studies of other methods of parsley leaves storage (drying and freezing paired with gamma irradiation in doses 0.7-2.7 kGy) showed that a dose of 2.7 kGy could be applied to parsley to promote antibacterial activity against Gram-negative bacteria _Escherichia coli_ and _Salmonella_ Typhimurium [43]. However, this high dose of gamma irradiation may affect the bioactivity of parsley, as well as its content of ascorbic acid, polyphenols, and antiradical capacity. Color is a very important quality parameter for edible leafy vegetables. The color changes in the parsley leaves after ozonation are presented in Table 3.  
The effects of the ozone treatments on L* values (lightness) of the leaves were significant for samples ozonated with 0.5 O\({}_{3}\) mg/L and 1.5 O\({}_{3}\) mg/L in both experiments: in ozonated water as well in ozonated water in a closed circuit. The L value for 30 g of parsley with a dose of 1.5 O\({}_{3}\) mg/L was statistically significantly higher. The average \(\Delta\)L* value for all treatments was lower than for the control sample, except for the sample of parsley after ozonation with 1.5 O\({}_{3}\) mg/L with 30 g of parsley, for which there were no statistically significant differences between the control parsley washed with water and parsley washed with ozonated water (Table 3). The higher L* values can be explained by the increase in light green color with treatment.