## 3 Results and Discussion
### Volatile Composition of Wines
In addition, compared to the pure fermentations (independently of used strains), sequential fermentation elicited higher concentrations of p-cymene, terpinolene, \(\beta\)-ionone, and (Z) and (E)-\(\beta\)-ocimene. Similar results, where different non-_Saccharomyces_ strains positively affected the transformation and release of varietal aromas, were previously reported for some aromatic grape varieties such as Muscat, Gewurztraminer, Sauvignon blanc, and Verdejo [9; 60; 61]. Although the total concentration of all terpen was higher for wines fermented by native strains (almost 1 mg/L and 0.9 mg/L for _C. famata_ WB-1 and _H. uvarum_ S-2, respectively) than for _S. cerevisiae_ QA23 fermentation alone (0.253 mg/L), the total ROC of terpen for the control sample was the highest. This finding can be explained by the lowest number of quantified key compounds with OAV above 1 in the control sample. Furthermore, the release and transformation of varietal compounds, which are specific for certain grape varieties and are mainly present in odorless form as aroma precursors [60; 61], is possible naturally during winemaking, but as a very slow process. Hence, finding and using yeast strains with enhanced glucosidase enzyme activity should be considered a good strategy for increasing the terpenoid aromas in wines. The PCA was used to visualize and reveal the diversity or common characteristics among the wine samples produced by different yeast strains (Figure 3). According to the PCA, four factors (principal components) had eigenvalues higher than 1, cumulatively explaining 99% of total variance of the initial data set. PC1 and PC2 comprised 74.52% of the variability. A clear differentiation among the Tamjanika wine samples can be observed, while it was found that samples fermented by the same yeast isolates were relatively similar because they were loaded closer to each other in the PCA plot. Methyl decanoate, methyl octanoate, phenylethyl alcohol, and linalool showed high negative loading scores in PC1 that distinguished both wine samples fermented by _H. uvarum_ S-2 from the other samples. However, samples fermented by _H. uvarum_ S-2 were negatively correlated with p-cymene and \(\beta\)-ocimene. On the other hand, Tamjanika wines produced in both inoculation protocols by _C. famata_ WB-1 were located in the lower right quadrant (positive values for PC1 and the negative for PC2). The wine produced in pure fermentation with _C. famata_ WB-1 was characterized by a higher relative contribution of acetate esters, isoamyl octanoate, and ethyl hexanoate. These compounds were related to fruit, herb, and pleasant aroma notes. The control wine sample was clearly different from the wine samples fermented by both native yeast strains in both inoculation protocols, with p-cymene as the compound that was considered most responsible for wine aroma. Figure 3: Principal component analysis (PCA) of volatile compounds (OAV \(>\) 1) from Tamjanika wine samples fermented in pure or sequential inoculation with _C. famata_ WB-1, _H. uvarum_ S-2, and _S. cerevisiae_ QA23 (SC). Data were the mean of two biological replicates of fermentation.