# Adding Flavor to Beverages with Non-Conventional Yeasts
## 3 Results
### Aroma Profiles of Fermentations
Based on the GC data, we generated relative quantifications of the volatile aroma compounds formed. The set of strains was then compared to the lager yeast _S. pastorianus/Weilenstephan_ to identify strains that produced higher amounts of esters and alcohols (Tables 3 and 4). One strain of _Saccharomyces cerevisiae_ (CBS 1250; E11) was a very good producer of alcohols, particularly of isoamyl alcohol, by contrast with lager yeast. Yet, this strain only produced moderate amounts of esters, mostly ethyl acetate. Its origin from sherry production suggests that it has been selected as the preferred strain for these fermentations. The _Wickerhamomyces anomalies_ isolates showed a remarkably high amount of both alcohol and ester production. Production of higher alcohols was strongly increased in these _W. anomalous_ strains compared to lager yeast. Interestingly, here mainly isoamyl alcohol and 2-phenyl ethanol production was increased. These represent two desirable flavors associated with banana and rose flavours. The sherry isolate (CBS 1250, E11) was found to produce even more isoamyl alcohol than the _W. anomalous_ strains, but far less 2-phenylethanol than these strains (Table 3). Yet, the _W. anomalous_ strains produced abundant amounts of esters, particularly ethyl acetate, isoamyl acetate and 2-phenylethyl acetate. Overall, these strains produced up to 10-fold more esters than the _Weilenstephan_ lager yeast strain. (Table 4). Another highly aromatic strain identified in this collection of strains was a _Pichia kluyveri_ strain, CBS 188. This strain produced almost fourfold more esters than lager yeast, while its aroma alcohols profile was similar to lager yeast with the exception of fourfold higher 2-phenylethanol production. Figure 2: Principal component analysis of the set of selected strains and their chemical compounds produced. The matrix is based on the set of 19 strains and the VOCs detected. Strains are presented with their assigned coordinates (see Table 1). Species belonging to the same genus are represented by the same color. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Strain Identifier** & **CBS1250** & **CBS262** & **CBS1082** & **CBS726** & **CBS261** & **CBS191** & **CBS188** & **CBS2568** & **CBS2649** \\ \hline Position & E11 & F11 & G3 & G4 & F10 & E9 & E7 & C7 & B7 \\ Species & _S. cerevisiae_ & _W. anomalous_ & _Z. bisporus_ & _Z. mollis_ & _W. anomalous_ & _P. membership/facims_ & _P. [PERSON]_ & _H. vinae_ & C. stellata_ \\ Butanol & 4.15 & 3.23 & 4.57 & 2.98 & 1.89 & 1.80 & 1.75 & 1.27 & 1.49 \\ Fatanezol & 1.81 & 0.00 & 3.49 & 2.07 & 0.00 & 0.00 & 0.00 & 0.00 & 1.82 \\ Isoamyl alcohol & 3.83 & 2.45 & 1.86 & 2.04 & 1.12 & 1.91 & 0.90 & 0.79 & 0.76 \\ Propanol & 4.28 & 1.18 & 2.19 & 2.37 & 1.68 & 0.00 & 2.04 & 1.87 & 0.00 \\ 2-Furanmethanol & 0.00 & 0.00 & 3.11 & 2.10 & 0.00 & 0.00 & 0.00 & 0.93 \\
2-Methyl propanol & 9.10 & 2.92 & 2.78 & 3.62 & 2.31 & 3.61 & 1.24 & 0.59 & 2.08 \\
2-Phenyl ethanol & 1.42 & 4.26 & 1.98 & 1.94 & 4.81 & 2.19 & 2.97 & 1.53 & 1.45 \\
3-(Methylthio)-1-propanol & 2.38 & 0.00 & 0.00 & 2.98 & 0.00 & 1.83 & 0.00 & 12.58 & 1.98 \\ \hline \hline \end{tabular}  
* The values reported represent the relative abundances of the specific subset of metabolites compared to the layer yeast strain (G10).  
\end{table} 
Table 3: Strains with higher aroma alcohol production than the _Weithersletplant_ layer yeast strain.