# Impact of Yeast Selection on Volatile Phenol Levels of Wines Produced from Smoked-Exposed Juice
## 3 Results and Discussion
### Volatile Phenol Analyses  
#### 3.2.1 Laboratory-Scale Yeast Trials  
The correlation between the volatile phenols of smoked Chenin Blanc wines and the various yeast treatments is shown in Figure 1. The PCA biplot of the 10 variables (volatile phenols) explains 86.82% (PC1 = 76.38% and PC2 = 10.44%) of the variance in the data set. The clustering indicates that the volatile phenol levels varied in the wines produced with the different yeast strains from the same base juice. The concentrations of the various volatile phenols of the Chenin Blanc wines are listed in Table S1. Wines produced with QA23 showed a positive association with guaicol (15.15 \(\upmu\)g/L), 4-methylguiaicol (12.58 \(\upmu\)g/L), 4-ethylguiaicol (5.36 \(\upmu\)g/L), phenol (29.89 \(\upmu\)g/L), \(p\)-cresol (5.00 \(\upmu\)g/L) and eugenol (1.46 \(\upmu\)g/L), and contained the highest levels of the respective volatile phenols (Figure 1 and Table S1). QA23 is a yeast known to have \(\beta\)-glucosidase activity ([PERSON] et al., 2009), which should lead to higher levels of volatile phenols in the presence of conjugated phenols. AWRI R2, VIN 7, BM4X4, Cross Evolution and Rhone 4600 also showed a positive association with the unwanted volatile phenols (Figure 1). While VIN 13, X16, UOA Maxithiol, X5, BDX and the spontaneous alcoholic fermentation displayed a negative correlation with the volatile phenols. The lowest guaicol concentrations were observed in wines fermented with VIN 13 (10.90 \(\upmu\)g/L) and X16 (10.82 \(\upmu\)g/L) (Table S1). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Treatment** & **Residual Sugar** & **Ethanol** & **Total Acidity** & **Malic Acid** & **Volatile** \\  & **(g/L)** & **(\% v/v)** & **pH** & **(g/L)** & **(g/L)** & **Acidity (g/L)** \\ \hline QA 23 (C 1) & 1.4 \(\pm\) 0.35 a & 13.3 \(\pm\) 0.17 abc & 3.46 \(\pm\) 0.02 ab & 5.6 \(\pm\) 0.17 b & 1.5 \(\pm\) 0.10 a & 0.23 \(\pm\) 0.01 b \\ QA 23 (S 2) & 1.0 \(\pm\) 0.35 a & 12.9 \(\pm\) 0.17 bc & 3.45 \(\pm\) 0.02 ab & 5.5 \(\pm\) 0.17 b & 1.4 \(\pm\) 0.10 a & 0.19 \(\pm\) 0.01 c \\ VIN 13 (C) & 0.7 \(\pm\) 0.35 a & 13.6 \(\pm\) 0.17 a & 3.46 \(\pm\) 0.02 ab & 5.9 \(\pm\) 0.17 ab & 1.6 \(\pm\) 0.10 a & 0.17 \(\pm\) 0.01 c \\ VIN 13 (S) & 0.3 \(\pm\) 0.35 a & 13.3 \(\pm\) 0.17 ab & 3.43 \(\pm\) 0.02 b & 5.6 \(\pm\) 0.17 b & 1.5 \(\pm\) 0.10 a & 0.17 \(\pm\) 0.01 c \\ X16 (C) & 1.9 \(\pm\) 0.35 a & 12.9 \(\pm\) 0.17 bc & 3.48 \(\pm\) 0.02 a & 5.9 \(\pm\) 0.17 ab & 1.5 \(\pm\) 0.10 a & 0.27 \(\pm\) 0.01 a \\ X16 (S) & 1.3 \(\pm\) 0.35 a & 12.8 \(\pm\) 0.17 c & 3.43 \(\pm\) 0.02 b & 6.2 \(\pm\) 0.17 a & 1.6 \(\pm\) 0.10 a & 0.24 \(\pm\) 0.01\(\pm\) \\ \hline \hline \(p\) & 0.851 & 0.021 & 0.131 & 0.071 & 0.570 & \textless{}0.0001 \\ \hline \hline \end{tabular}  
* C: Control, no smoke exposure, 2 g: Smoke treatment. Each value represents the mean of three replicates (\(\pm\)standard error of the mean). Means in columns followed by different letters are significantly different (\(p\leq 0.05\)).  
\end{table} 
Table 3: Enological parameters and probability (\(p\)) values of Chenin Blanc wines produced from smoked and unsmoked juice using three commercial wine yeasts. The correlation of volatile phenol levels of smoked Merlot wines produced with different yeasts are shown in Figure 2. The PCA biplot explains 74.32% (PC1 = 58.60% and PC2 = 15.72%) of the variance in the data set. As observed with the Chenin Blanc wines, the volatile phenol levels varied in the Merlot wines produced with the different yeast strains. Wines that underwent spontaneous alcoholic fermentation showed a positive association with guaiacol (8.21 ug/L), 4-methylguaiacol (4.56 ug/L), 4-ethylguaiacol (2.35 ug/L), 4-ethylphenol (0.77 ug/L), 2,6-dimethyl phenol (1.81 ug/L), 0-cresol (2.38 ug/L) and \(p\)-cresol (2.25 ug/L), and contained the highest concentrations of most of these volatile phenols (Figure 2 and Table S2). D254, Clos, NT 50, QA23, Exence, D21 and AWRI 796 showed a positive association with most of the volatile phenols (Figure 2).