## 3 Results and Discussion
### Viability  
[PERSON] and [PERSON] [12] reported that the survival of yeast during rehydration depends on osmotic pressure, yeast cell temperature and rehydration medium. In the presented studies, the analyzed yeast strains differed significantly in the viability of yeast cells after rehydration. Studies by other scientists have shown that yeast cell viability after rehydration can range from 60-85% [27]. The control sample of the fresh strain of _Sc_ US-05 rehydrated with CW showed the highest viability (76.6%). In the case of fresh culture, no significant differences were observed in the improvement of viability after using PTW for rehydration. This proves that fresh yeast does not require the use of factors improving its quality. In the case of rehydration in the presence of PTWN, a significant reduction in viability was observed in this strain. The lowest viability for yeast samples rehydrated with CW was observed for _Sc_ S33 strain (22.8%). The yeast viability after rehydration in the presence of PTWN differed significantly from control samples (CW); after 45 min of rehydration in PTWN medium, a significant decrease in viability was observed. _Sc_ S33 strain was characterized by the lowest viability (18.6%), which, according to the literature, was not enough for efficient fermentation [28]. Notably, _Sc_ T58 and S33 yeast strains rehydrated with PTWAir were characterized by improved viability in comparison to control samples. The results showed that ale yeast strains (T58, US-05) after rehydration in PTWs were similar to the results obtained by [PERSON] et al. [8]. [PERSON] et al. [26] obtained a 98% viability result for the lager strain _Sp_ W30/70, which was much higher than those results obtained in our studies due to the used dry lager yeast being kept refrigerated for a longer time, and even the application of PTWs did not improve this parameter. In this case, both rehydration in the presence of PTWAir and PTWN contributed to a significant reduction in the viability of lager yeast compared to the control sample. We also checked the viability of the analyzed rehydrated cultures after the fermentation process (Table 3). The viability of the yeast biomass after the end of fermentation depended on the used yeast strain and used rehydration medium; however, the same trends were found as those observed for the rehydrated yeast. Between individual control samples (CW), the fresh quality yeast strain of _Sc_ US-05 (84.5%) had the highest viability, and the poor quality yeast strains of _Sc_ T58 (70.1%) and _Sc_ S33 (68.8%) had the lowest viability. In the case of PTWAir samples, the _Sc_ US-05 strain had the highest viability after fermentation, and the _Sc_ S33 strain the lowest. In each yeast strain, PTWN significantly contributed to the reduction in viability compared to the control samples (CW). The obtained results may be caused by active forms of nitrogen that were created during the plasma-treated water process [22], which negatively influenced the ability of cells to reproduce during the entire fermentation process. On the other hand, PTWAir did not change the viability of cells in the given strains as compared to the control samples (CW). In the research conducted by [PERSON] and [PERSON] [29], the viability of yeast ale after the fermentation process was completed was higher than 90%; similar results for lager yeast were obtained by [PERSON] and [PERSON] [30]. For the results presented in the article, the most similar result was obtained for the fresh quality yeast strain of _Sc_ US-05 for the samples after rehydration in the presence of PTWAir (83.3%) and CW (84.5%).