# The Application of Wood Species in Enology: Chemical Wood Composition and Effect on Wine Quality
## 4 Influence of Wood Species on the Wine Sensory Profile
In the literature, several research works studied the impact of aging red wine in oak wood barrels on the wine sensory characteristics [14; 32; 33; 96; 104]. In this sense, it was shown that in the case of red wines aged for 12 months in oak wood barrels that the kind of oak wood barrels used and the barrel toasting process influenced the wine sensory characteristics [96]. The descriptors vanilla aroma, astringency sensation, and bitterness taste are significantly influenced by the barrel toasting process. These researchers also showed that the wood origin influenced the sensory characteristic of the wine, as it was shown that the concentration of the extractable compounds is different, mainly on whiskey lactone and eugenol concentration. Moreover, differences were observed if the wines were aged in new or used barrels. [PERSON] et al. [104] showed that all sensory descriptors of wines aged in new oak barrels are significantly different from wines aged in used oak barrels. The wines aged in new barrels were higher scored in the descriptors woody, vanilla, spicy, and cedar notes, and the wines aged in used barrels were higher scored for the descriptors pharmaceutical, herbaceous and horsy notes. [PERSON] et al. [74] assessed the sensory profile of Syrah wines aged twelve months in barrels from diverse wood species. It was shown that each wood species contributed with diverse intensities of practically all gustative and aromatic descriptors. Regarding the olfactory descriptors, these authors showed that the wines aged in oak barrels presented the highest intensity of vanilla (4.6), almond/caramel and toasty notes, wines aged in false acacia wood barrels of spicy, smoky, and fruity notes, and the wines aged in ash wood barrels of balsamic notes. The scores for a vanilla descriptor for the wines \begin{table}
\begin{tabular}{c c c c} \hline
**Compounds** & **ODT (\(\mu\)g/L)** & **Sensory Descriptors** & **Reference** \\ \hline \multirow{2}{*}{Furfural} & \multirow{2}{*}{15,000–20,000} & Toasted nuts, burnt almonds, & \\  & & caramel, dried fruit & \\ \hline
5-Methyl furfural & 16,000–45,000 & Toasted nuts, toasty, sweet, spicy & [129; 130; 131; 123] \\ \hline \multirow{2}{*}{\begin{tabular}{c} Vanillin \\ phenols \\ \end{tabular} } & \multirow{2}{*}{60–320} & Vanilla & [123; 131] \\ \hline \multirow{2}{*}{\begin{tabular}{c} Syringaldehyde \\ \end{tabular} } & \multirow{2}{*}{50,000} & Vanilla & [123] \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} Eugenol \\ \end{tabular} } & \multirow{2}{*}{5–500} & Spice cloves, cinnamon, smoke & \\  & & character & [123; 129; 130; 131] \\ \hline \multirow{2}{*}{
\begin{tabular}{c} Guaiacol \\ \end{tabular} } & \multirow{2}{*}{15–75} & Spicy, toasty, smoky/burnt & [123; 132; 133] \\ \hline
4-Methylguaiacol & 65 & Burnt & [123] \\ \hline \(\beta\)-Methyl-\(\gamma\)-octolatones & & Coconut & [123] \\ \hline Isomer _cis_ & 35–46-92 & Vanilla, oaky, clove, coconut & [133; 133; 131; 127] \\ \hline Isomer _trans_ & 122–460 & Vanilla, oaky, clove, coconut & [131; 128; 132] \\ \hline
4-Ethylphenol & 620 & Horse sweat & [125] \\ \hline \multirow{2}{*}{
\begin{tabular}{c} 4-Ethylguayacol \\ \end{tabular} } & \multirow{2}{*}{140} & Toasted bread, smoky, clove, & \\  & & burnt & [125; 130] \\ \hline Acetovanillone & 1000 & Vanilla & [134] \\ \hline Maltol & 5000 & Caramel, toasted & [135] \\ \hline \end{tabular}
\end{table} 
Table 7: Wood compounds and their sensory descriptors and olfactory detection threshold (ODT). aged in ash wood was 1.8 and for the wines ages in chestnut wood, 1.6. However, these authors pointed out that the levels of vanillin were higher in wines aged in ash, followed by those aged in chestnut and oak wood and those aged in cherry and false acacia wood barrels. According to these researchers, the results showed that the olfactory descriptors for vanilla need to be enriched by the existence of other compounds, such as whisky lactones, compounds that are only found in wines aged in oak wood barrels. Previously, [PERSON] et al.