# Chemical and Sensory Characterization of Vidal Icewines Fermented with Different Yeast Strains
## 3 Results and Discussion
### Chemical Analysis
#### 3.3.2 Chemical Characteristic of Icewines Fermented by Different Yeasts  
Among the 485 volatile compounds identified in all icewine samples, not all of them have aroma contributions, and the study of flavor pays more attention to the compounds with aroma contributions [27]. Therefore, based on the qualitative results and matched it with the aroma substance database (Flavornet, [[http://www.flavornet.org/flavornet.html](http://www.flavornet.org/flavornet.html)]([http://www.flavornet.org/flavornet.html](http://www.flavornet.org/flavornet.html)), accessed on 11 December 2018), 156 volatile compounds were selected to further analyze, details can be seen in Table S2. The semi-quantitative results were obtained by the internal standard method and then drawn on a heat map (Figure 2). In the figure, the rows represent the compounds, and the columns represent the yeasts used for fermentation. The distance measure used in clustering rows (compounds) was the Euclidean method, and the data were standardized before cluster analysis. According to the results of heat map analysis, the 156 compounds can be divided into three classes, the compounds of class A were the highest content in R2 yeast fermented icewine, class B substances were highest in ST yeast fermented icewine, and class C aroma components had the highest content in K1 and EC1118 yeast fermented icewine. In class A, most of the compounds were esters, alcohols, terpenes, and carbonyl compounds. In this group, ethyl 2-methylbutyrate, ethyl isobutyrate, ethyl octanoate, and ethyl caproate were all the major aroma contributors in Vidal icewine, which smells similar to the apple, pineapples, and so on. In addition, the 1-octen-3-ol and 1-octen-3-one showed a mushroom characteristic, 1-hexanol showed a resin characteristic, \(\beta\)-damascenone, linalool, and geraniol with the aroma characteristics of honey, lavender, and rose, respectively. \(\alpha\)-Terpinene, \(\gamma\)-terpinene, and 1,4-cineole were the aroma characteristics of pine. Benzaldehyde showed the aroma characteristics of almonds. These compounds were all key aroma compounds reported in Vidal icewine [4; 20], especially \(\beta\)-damascenone, which has been reported in many studies that is the strongest aroma in Vidal icewine [4; 20; 28]. In red wines, \(\beta\)-damascenone has been found to enhance fruit aroma while can also inhibit the plant aroma produced by methoxypyrazine [29]. Similar phenomena have also been found in the study of icewine, \(\beta\)-damascenone not only affects the perception of honey but also affects the perception of other aromas such as apicalor peach [4]. Class B is mainly composed of aromatic compounds and ester compounds, including seven aromatic compounds, six ester, four alcohol, six aldehydes and ketones, two nitrogen compounds, and one volatile phenol, of which phenethyl acetate (flowers), homofuranol (sweet), ethyl valerate (fruit) were reported as the important aroma compounds in icewine [4]. Class C compounds gather all lactones, which usually have aroma characteristics such as apricot [4]. From the above analysis, we can see that some key aromas, which has reported on Vidal icewine were significantly higher in R2 than other samples, such as 1-octen-3-ol, 1-hexanol, \(\beta\)-damascenone, linalool, geraniol, 1-octen-3-one, and so on, and the alcohol, ester, and carbonyl compounds in the wine also had obvious advantages. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **K1** & **EC1118** & **ST** & **R2** \\ \hline Esters & 97 & 91 & 93 & 117 \\ Alcohols & 79 & 81 & 73 & 105 \\ Ketones & 50 & 49 & 46 & 55 \\ Aromatic compounds & 34 & 35 & 32 & 31 \\ Tepenes & 25 & 24 & 24 & 26 \\ Aldehydes & 18 & 23 & 14 & 26 \\ Furans & 18 & 19 & 19 & 23 \\ Acids & 19 & 21 & 19 & 22 \\ Nitrogen-containing compounds & 17 & 21 & 10 & 18 \\ Phenols & 17 & 18 & 17 & 17 \\ Lactones & 11 & 11 & 11 & 11 \\ Sulfides & 6 & 6 & 6 & 6 \\ Total & 391 & 399 & 364 & 457 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Volatile compounds in Vidal icewine fermented by different yeasts.