## 3 Results and Discussion
### Analytical Parameters of the Experimental Beers
On average, the beers obtained by AW fermentation contained more volatile acidity than other samples, although the highest level was found in samples obtained with the P4-CZ3 mixed starter in WW. This starter also yielded the highest level of volatile acidity among PW samples, whereas in AW fermentation, the highest volatile acidity was detected in samples fermented with the mixed starter containing the _T. delbrueckii_ strain (P4-LC2-1). The alcohol content of all the beers ranged from 2.63 to 3.25% (_v/v_), with significant differences in the function of starters and beers. In order to verify if the differences in ethanol content were due to significant differences in residual sugar, ANOVA was carried out on the final real extract, expressed as \({}^{\circ}\)P. The results showed that the residual sugar in all the beers was not significantly different (data not shown). These results indicate that the differences in the ethanol content of final experimental beers were mainly related to the starter cultures performing the fermentation processes. All the beers produced by mixed fermentation exhibited a lower alcohol content than the beers obtained by pure fermentation with _S. cerevisiae_ P4, with the exception of the starter P4-CR1 in Amber beer. In particular, the beers produced by the mixed culture P4-CZ3 exhibited the lowest values of AC in all the tested ports (2.80% _v/v_, 2.63% _v/v_ and 3.08% _v/v_ in PW, WW and AW, respectively). Figure 3 summarises the ethanol reduction obtained across all of the mixed fermentation trials, calculated as difference between the alcohol content in beers obtained from each mixed starter and the ethanol content of beers obtained with the P4 starter. The highest reduction was observed in WW fermentations for almost all the mixed cultures, except P4-TSF. The mixed starter P4-CZ3 had the highest reduction in all the beers produced (ethanol reduction of 0.29 in PW, 0.47 in WW and 0.11 in AW). These results indicate that the _C. zemplinina_ strains tested in this study, mainly the CZ3 strain, might be promising yeast starters for the production of low-alcohol beers. Figure 3: Alcohol reduction in the beers produced by the mixed cultures (P4-CR1, P4-LC2-1, P4-TSF, P4-CZ3) in the three different sorts (PW, WW, AW). These values were calculated as difference between the alcohol content in beers obtained from each mixed starter and the ethanol content of beer obtained with the pure starter (P4). Data with different superscript letters (a, b) within each trial are different according to [PERSON]’s test (\(p\leq 0.05\)). This species has been extensively tested in wine fermentation owing to its fermentative behaviour, both for the production of low-alcohol wines and for its positive contribution to the overall sensory quality of wine, whereas very few studies have been available until now on the use of this yeast species in brewing. [PERSON] et al. (2018, 2019) investigated the application of a _C. zemplinina_ strain, isolated from overripe grapes for craft beer production in different word extracts. When tested in malt wort alone, this strain of _C. zemplinina_ produced a low-alcohol beer (1.5% _v/v_), confirming the inability of this species to ferment maltose. Instead, the use of different adjuncts had a different effect on ethanol production, with a high increase in ethanol production when apple juice was used as an adjunct. This study demonstrated that _C. zemplinina_ could be suitable for the production of craft beer with new sensory characteristics using innovative adjuncts, and for production of low-alcohol beers by using word without the use of adjuncts. Conversely to _C. zemplinina_ strains, the mixed starter containing the _Z. bailii_ strain (P4-CR1) was less efficient for ethanol reduction, as it yielded the lowest reduction in the PW and WW fermentations. In AW fermentation, this mixed starter produced beer containing a higher level of alcohol than beer obtained by using the single starter P4. _Z.