## 3 Results and Discussion
### Volatile Compounds-Wine Sensory Evaluation  
At the end of grape must fermentations with the commercial Passion Fruit strain and the wild-type LMBF Y-54 strain cultured on Assyrtiko and Mavrotragano grape musts, the volatile compounds were analyzed with GC-MS (SPME) analysis. More than 100 volatiles have been identified, belonging to five major chemical group compounds from acids, aldehydes, ketones, esters and higher alcohols and as far as Assyrtiko is concerned the results are in agreement with other studies of the literature [7]. Mavrotragano is a rare indigenous _Vitis vinifera_ Greek grape variety mostly unexploited, while the literature regarding its volatile composition is limited. The average (%) contribution of these groups of compounds for both Assyrtiko and Mavrotragano wines are presented in Figure 7. The ester group was comprised by the highest number of volatile compounds [65] and had the higher percentage of contribution to the volatile content of wines followed by higher alcohols. Esters are considered a significant group of volatile compounds as they pose a major impact on flavor and aroma of alcoholic beverages, while a plethora of esters is also produced during fermentation as a result of yeast metabolism [66; 67]. Esters mainly contribute to the aromatic profile of wine via fruity and floral odors [65; 67]. In the present study, no significant differences were found among the relative contents of esters between the commercial (Passion Fruit) and wild-type (LMBF Y-54) yeast strain in both white and red wines. Figure 7: _Cont._ \begin{table}
\begin{tabular}{c c c c} \hline
**Yeast Strain** & **Carbon Source** & **Initial Sugar (g/L)** & **EtOH (g/L)** & **Reference** \\ \hline _S. cerevisiae_ LMBF Y-54 & Glucose & 200 & 68.0 & Current study \\ _S. cerevisiae_ Cross X & Glucose & 200 & 82.2 & Current study \\ _S. cerevisiae_ Passion Fruit & Glucose & 200 & 91.1 & Current study \\ _S. cerevisiae_ LMBF Y-54 & Grape must Assyrtiko & 222 & 106.3 & Current study \\ _S. cerevisiae_ LMBF Y-54 & Grape must Mavrotragano & 214 & 99.7 & Current study \\ _S. cerevisiae_ Passion Fruit & Grape must Assyrtiko & 222 & 102.7 & Current study \\ _S. cerevisiae_ Passion Fruit & Grape must Mavrotragano & 214 & 97.8 & Current study \\ \hline \end{tabular}
\end{table} 
Table 3: _Cont._Figure 7: _Cont._  
Statistical differences were only observed among the white (Assyrtiko) and red wines (Mavrotragano) in terms of their ketone and aldehyde contents. In more detail, significantly lower contribution of the two groups of compounds mentioned above were observed in red wines irrespectively of the yeast strain used. This can be attributed to the higher phenolic content of red wines and consequently their higher antioxidant activity which exerts a protective role on oxidation phenomena, thus preventing the oxidation of carbonyl compounds to their corresponding acids [7]. Interestingly, the volatile composition of either red or white wines produced by the LMBF Y-54 and commercial strains did not differ significantly, verifying the high potential of the novel Y-54 strain to produce high-quality wines. The results from the GC-MS analysis are in line with the sensory data. Specifically, no statistically significant differences were observed between the results for the \"control\" wines (_viz._ the ones produced with the commercial Passion Fruit yeast strain implicated in the fermentation) and the wines made with the newly isolated and studied yeast strain (LMBF Y-54). Statistically significant differences were only observed concerning fresh and dried fruit odors; however, these differences were between red and white wines and not between the yeast stains studied in this experiment. Moreover, the aroma of all wines examined was of medium intensity with a fresh fruity and floral character and absence of defects, while the overall quality was rated as very high confirming the high potentiality of the novel yeast strain on the wine-making process (Figure 8). Figure 8: Sensory data of wine samples. Y-54/A: Assyrtiko wine made with _S.