# Influence of Yeast Strain on Odor-Active Compounds in Fiano Wine
## 3 Results and Discussion
### Gas Chromatography-Olfactometry Analysis
“Fiano” fermented in oat barrels using four different yeast strains, three _S. cerevisiae_ and one _S. bayanus_, compared to the control without yeast inoculation. All four selected yeasts had a much lower AEDA value for diacetyl, which is described as being associated with \"butter\" notes. Similarly, several compounds--some of which were not identified--were lower in the selected yeast trails compared to the control, namely a compound described as \"roasted/nutty\", 3-methylthio-1-propanol, a non-identified compound described as \"medicinal/phenolic\" and a compound described with \"smoked\" notes. On the other hand, the control sample generally had lower values for 1-propanol (fruity, sweety), the N.I. compound n. 27 (\"floral/rose\" description) and a very few others. For those compounds described as \"smoked/phenolics\", it was difficult to find a general trend, as several compounds like the N.I. volatiles n. 24 and 40 had high value in CY3079. This yeast also resulted in a wine with lower value for 4-vinylguaiacol and 1-propanol. In the case of QA23, higher AEDA values compared to the other yeast strains and the control were obtained for 1-propanol, while lower values were recorded for 2-propylfuran and 3-methylthio-1-propanol. Wines fermented using yeast D47 had lower values for the N.I. compound n.1, ethyl hexanoate and acetophenone, while lanalool and hydroxy diethyl butanoate had higher values. Yeast VL1 resulted in wines with much higher values of the N.I. compound n. 1 described as \"fruity\", while compounds described as \"floral\" or \"honey\" had low values, namely the N.I. compounds n. 41 and 43, and phenylacetic acid. Additionally, some compounds described with a \"smoked/phenolic\" note had lower AEDA value, i.e., syringol and N.I. volatile n. 40. In order to understand how the odor active compounds could affect the global sensory characteristics of a wine, aromatic series were constructed on the available data. An aromatic series is defined as a group of volatile compounds sharing the same, or similar, aroma descriptor [32]. Generally, the value of an aromatic series is obtained by the sum of the OAVs of the selected volatile compounds. The OAV is obtained by dividing the concentration of each volatile compound by its perception threshold [33]. The series used in this experiment were built by grouping the odor compounds as previously mentioned and reporting the sum of the AEDA values (expressed as log\({}_{10}\) value) detected by GC/O analysis (Table 2). Because of the high complexity of the olfactory perception, some aroma compounds were included in two or more odorant series such that their AEDA values could be better linked to the sensory perceptions, based on literature data [34; 35; 36]. Accordingly, fruity, floral, wines, vinegar, butter/cheese, caramel, honey, smoked, phenolic and nutty/toasty odor series were built (Table 2). These odor descriptors can be useful to better show the potential aromatic impact of the different yeasts. The results of this approach are shown in Figure 1.  
For yeast QA23, the major difference compared to the control wine was obtained for the \"fruity\" attribute, with QA23 leading to a statistically significant (\(p<0.05\)) higher value, while lower values were obtained for \"phenolic\" and \"honey\", and only a minor difference for \"butter/cheese\". These results were very similar to those obtained from the yeast strain D47, which led to a slight stronger decrease in the phenolic, honey and smoked notes. On the other hand, both CY3079 and VL1 had an opposite trend. The former had almost the same level of the \"fruity\" value and a lower \"floral\" value, while the latter led to the highest \"fruity\" value and the lowest value of \"floral\" of all the five samples. As a general trend, all selected yeast strains resulted in wines with a higher value for the \"fruity\" attribute, but two of them had lower \"floral\" notes compared to the control. The \"phenolic\" note was in any case lower, with VL1 having the lowest value of this attribute.