# Aromatic Potential of Diverse Non-Conventional Yeast Species for Winemaking and Brewing
## 3 Results and Discussion
### Microwine
#### 3.1.2 Aroma Profiles  
Table 4 shows the aroma profile of resulting microwines. The impact on aroma synthesis of non-_Saccharomyces_ strains as a pure and mixed culture was studied employing multifactorial ANOVA. The type of culture, either pure or mixed, affected the production of all the aroma compounds except for ethyl caprate. In addition, the impact of non-conventional strains on acetate esters, phenylethyl alcohol and ethyl caprylate was significant. Higher alcohols contribute to floral, fruity or herbal aromas depending on their synergistic effects with other flavour-active compounds. In higher concentrations they could also influence flavour release and contribute to mouthfeel. Some of the most important higher alcohols in alcoholic beverages are isobutyl alcohol (solvent, fusel, spiritous), isoamyl alcohol (harsh, nail polish, banana) and phenylethyl alcohol ( floral, rose, sweet), presenting, respectively, 40, 30 and 10 mg/L sensory thresholds in wine [13]. Excessive amounts of these compounds can be detrimental to wine quality; however, moderate amounts increase wine complexity [18]. Multifactorial ANOVA showed that the type of culture (pure or mixed) was a significant factor regarding higher alcohol yield. Contrarily, the non-_Saccharomyces_ yeast participating in the fermentation did not influence the quantity of higher alcohols, except in the case of phenylethyl ethanol, where differences of even 8-fold were observed. Isobutyl alcohol was above its sensory threshold in all of the mixed fermentations whereas isoamyl alcohol only in some of them (Table 4). In all these cases, the amount of the two alcohols were higher than in the corresponding pure non-_Saccharomyces_ cultures and even higher than in the reference microwine, where the amounts of these alcohols were below their sensory thresholds (Table 4). Mixed fermentations carried out with _Hanseniaspora guilliermondii_ CBS 2567, _T. microellipsoides_ CBS 6641, _Zygosaccharomyces_ Kombuchaensis_ CBS 8849 and _Zygosaccharomyces_ rouxii_ CBS 9716 had much higher isobutyl alcohol levels and _Barnettozyma california_ CBS 8860 had higher isobutyl and isoamyl alcohols amounts compared to the reference culture (Table 4). In previous works, intensive production of isobutyl and isoamyl alcohols was already seen in some of the non-_Saccharomyces_ strains tested here, such as _H. Guilliermondii_ CBS 2567 and _T. Microellipsoides_ CBS 6641 when used as pure cultures in standard growth medium [22]. In this previous work, _H. guilliermondii_ yielded 27 and 2.3 times the average quantity of isobutyl alcohol compared to _Saccharomyces_ strains and _W. subpelliculosus_ CBS 5552 produced 8 times the average quantity of isoamyl alcohol compared to _Saccharomyces_ strains. Furthermore, the high production of alcohols by _Z. kombuchaensis_ CBS 8849 has already been observed by other authors in pilot-scale sequential fermentations [3], suggesting a proper match between microscale and pilot scale regarding aroma profile. It is worth mentioning the synergistic effect between reference strain and strains _Starmera caribaea_ CBS 7692 and _B. californica_ CBS 8860 regarding isoamyl alcohol production, since the amount of this alcohol in mixed fermentations was higher than the addition of quantities yielded by each strain separately (Table 5). On the contrary, phenylethyl alcohol levels were higher in pure cultures, being above its sensory threshold in all cases except for _S. caribaea_ CBS 7692 and with these differences being significant in the case of _Galactomyces_ geotrichum_ CBS 772.71, _W. Subpelliculosus_ CBS 5552, _T. microellipsoides_ CBS 6641, _S. caribaea_ CBS 7692 and _K. gamospora_ CBS 10400 (Table 5). In mixed cultures, the amounts of this alcohol were below its sensory threshold with the exception of CBS 8031 (_Hanseniaspora vineae_). However, the reference microwine contained the highest phenylethyl alcohol level (Table 5). \begin{table}
\begin{tabular}{l l l l l l l l l l l l l l} \hline \hline
**Strain 1** & **Strain 2** & **Ratio** &