# Adding Flavor to Beverages with Non-Conventional Yeasts
## 3 Results
### Aroma Profiles of Fermentations  
In total, we identified 62 different volatiles in the samples of all strains (Table 2). Major volatile-aroma compounds that were detected included esters, alcohols, aldehydes, ketones and acids. Most species harbor the ability to produce a large variety of flavors. Thus, we did not identify single species that produced only very few compounds or species with a very high diversity, as shown in Figure 1 for a selection of species. However, there was an enormous difference in the amounts of specific volatiles produced. Esters were the most prominent group of volatiles. In total, 22 different esters could be identified and within this group ethyl-esters dominated, such as ethyl hexanoate and ethyl acetate, associated with fruity wine/apple-like and sweet pear drop flavors, respectively. Alcohols comprised the second major group of compounds. Besides ethanol, we identified 14 different alcohols. Yet, only two compounds, 2-phenylethanol, perceived as rose flavor, and isoamyl alcohol, a banana-like flavor, were produced by all strains analyzed. During anaerobic fermentations the formation of aroma alcohols is favored over the production of aroma acids [19]. In line with this, we identified only six acids, of which acetic acid and butyric acid were prominent. \begin{table}
\begin{tabular}{c c} \hline \hline
**Number** & **Alcohols** \\ \hline
1 & Benzyl alcohol \\
2 & Butanol \\
3 & Dodecanol \\
4 & Fenchyl alcohol \\
5 & Furaneol \\
6 & Isoamyl alcohol \\
7 & Propanol \\
8 & 2-Ethyl-1-hexanol \\
9 & 2-Furannmethanol \\
10 & 2-Methyl propanol \\
11 & 2-Nonanol \\
12 & 2-Phenyl ethanol \\
13 & 3 Ethoxy-1-Propanol \\
14 & 3-(Methylthio)-1-propanol \\ \hline \hline \end{tabular}
\begin{tabular}{c c} \hline \hline
15 & Butyl acetate \\
16 & Ethyl (4E)-4-decenoate \\
17 & Ethyl 2-methylbutyrate \\
18 & Ethyl acetate \\
19 & Ethyl butanoate \\
20 & Ethyl decanoate \\
21 & Ethyl dodecanoate \\
22 & Ethyl heptanoate \\
23 & Ethyl hexadecanoate \\
24 & Ethyl hexanoate \\
25 & Ethyl isobutyrate \\
26 & Ethyl isovalerate \\
27 & Ethyl octanoate \\
28 & Ethyl propanoate \\
29 & Ethyl tetradcanoate \\
30 & Isoamyl acetate \\
31 & Isoamyl butyrate \\
32 & Isobutyl acetate \\
33 & Isobutyl butanoate \\
34 & Phenethyl acetate \\
35 & _S_-methyl thioacetate \\
36 & 2-Methyl propanoate \\ \hline \hline \end{tabular}
\end{table} 
Table 2: List of 62 volatiles that were detected by GC/MS measurement. \begin{table}
\begin{tabular}{c c} \hline \hline
**Number** & **Alcohols** \\ \hline  & Acids \\ \hline
37 & Acetic acid \\
38 & Butyric acid \\
39 & Decanoic acid \\
40 & Hexanoic acid \\
41 & Isovaleric acid \\
42 & Octanoic acid \\ \hline  & Aldehydes \\ \hline
43 & Acetaldehyde \\
44 & Benzaldehyde \\
45 & Furfurral \\
46 & Phenyl acetaldehyde \\
47 & 1-Decanal \\
48 & 1-Nonanal \\
49 & 3-Methyl butanal \\
50 & 4-Methyl benzaldehyde \\
51 & 5 Methyl furfurral \\
52 & 5-Hydroymethylfurral \\ \hline  & Ketons \\ \hline
53 & Acetoin \\
54 & Diacetyl \\
55 & Pyranone \\
56 & 2-Cyclopentene-1,4-dione \\
57 & 2-Dodecanone \\
58 & 2-Methyltetrahydro-orthiophen-3-one \\
59 & 2-Nonanone \\
60 & 2-Undecanone \\ \hline  & Pyrazines \\ \hline
61 & 2,5-Dimethyl-3-ethylpyrazine \\
62 & 2,6-Dimethylpyrazine \\ \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
Figure 1: Number of volatile organic compounds (VOCs) produced during fermentation of selected strains. The compounds were grouped, numbered and colored according to their chemical class. The complete list of compounds is shown in Table S1 (see Table 1 for nomenclature of strains). We were most interested in species that separated well from _S. cerevisiae_ or lager yeast strains. Therefore, we narrowed down the selection of strains to those that showed clear separation in their flavour profiles to the set of _S. cerevisiae_ and lager yeast strains based on principal component analysis (Figure 2). This identified species belonging to the genera _Candida_, _Pichia_ and _Wickerhamomyces_.