## 3 Results and Discussion  
### Reduction in Microbial Counts and Shelf Life of Juice  
The average levels of contamination of fresh samples of carrot juice with aerobic mesophilic microorganisms and yeast were 3.6 and 0.73 log\({}_{10}\) CFU/mL, respectively. In the present study, the shelf life of juices after 24, 48, and 72 h was determined on the basis of the criterion of the permissible content of mesophilic aerobic microorganisms in pasteurized fruit and vegetable juices, as specified in the Regulation of the Polish Minister of Health of 13 January 2003 [32]. In accordance with the Regulation, the allowable number of mesophilic aerobic microorganisms should be lower than or equal to 3.0 log\({}_{10}\) CFU/mL and in the range of 3.0-4.0 log\({}_{10}\) CFU/mL in a maximum of two out of five samples from one batch. A microbial count exceeding 4.0 log\({}_{10}\) CFU/mL disqualifies the entire batch of the product. It is also assumed that the allowable yeast and mold content in pasteurized juices can be equal to or lower than 1 log\({}_{10}\) CFU/mL. The results of the microbiological analyses of cold-stored fresh carrot juice treated with cold atmospheric plasma and/or supplemented with sumac powder are shown in Table 2.  
The comparison of the results of microbiological cultures with the permissible levels specified in the legal regulations on the microbiological quality of pasteurized juices indicates that the total number of aerobic microorganisms in the fresh carrot juice was exceeded at 24 h after pressing. A further increase in the number of microorganisms was observed during the subsequent hours of storage; therefore, the analyzed carrot juice was unsuitable for consumption [32]. The addition of sumac powder and the plasma treatment of the freshly squeezed juice samples proved to be effective in limiting microbial growth, but this effect was clearly dependent on the sumac concentration and plasma treatment time. The analyses showed that the supplementation of the carrot juice with 0.5% and 3.0% of sumac powder and the plasma treatment reduced the number of microorganisms. The total number of aerobic microorganisms in juice samples S05 and S3 detected at the specified time points decreased on average by 0.14-2.78 log\({}_{10}\) CFU/mL in comparison with the corresponding control samples. The number of bacteria in the plasma treatment variant (sample code P) decreased on average by 0.81-3.01 log\({}_{10}\) CFU/mL. In turn, the amount of yeasts decreased by a maximum of 1.11 log\({}_{10}\) CFU/mL in sample S05, 2.80 log\({}_{10}\) CFU/mL in sample S3, and 4.17 log\({}_{10}\) CFU/mL after the plasma treatment. The largest decrease was observed after 72 h of refrigerated storage. The data shown in Table 2 indicated a high level of significant (according to the statistical test) reduction in the microbial count induced by the experimental treatments. However, these juices did not meet the requirements specified in the Polish Minister's Regulation [32]. The supplementation of the juice with 0.5% of sumac powder and the plasma treatment (SP05) or the use of the additive after the plasma exposure yielded in better results (2.58-4.76 log reduction in aerobic mesophilic microorganisms), although they were not satisfactory in terms of extending the microbiological shelf life of the juice at 24 h after pressing, due to the presence of yeast above 1 log\({}_{10}\) CFU/mL [32]. What is noteworthy is that given the microbial growth in the control samples during storage and the inhibition of the growth of microorganisms in the plasma-treated samples (before or after the sumac powder addition), the greatest reduction in the number of microorganisms was recorded