## 6 Influence of Ageing Factors on the Coumarin Contents of Spirit Beverages
### Wood  
The wood from the European oak species _Quercus robur_ L. is predominantly used for the ageing of wine spirit [19, 62], brandy [191] and some grape marc spirits [18], while _Quercus alba_ L., from North America, is commonly used in the ageing of Bourbon and Tennessee whiskers [14, 23, 192], brandy [70, 191] and rum [13, 27, 193]. Other botanical species, such as _Quercus sessiliflora_ [PERSON], _Quercus pyrenaica_ [PERSON] and _Quercus figinea_ [PERSON], grown in Mediterranean countries, are used in brandy ageing [21] and grape marc spirit ageing [18]. Chestnut wood (_Castanem sativo_ Mill.) is also a valuable resource for this purpose in wine spirit [19] and brandy [21]. As far as whiskey is concerned, the production of this beverage in Scotland and Ireland is mainly based on barrels that have already been used for the ageing of Bourbon whiskey, Sherry wine and Brandy de Jerez, and Port wine and Madeira wine, imported from the USA, Spain and Portugal, respectively [14, 192], and therefore the American and European oak species also influence its chemical composition, specifically the phenolic one, including the coumarin contents. In contrast, cachaca in Brazil is aged in oak wooden barrels but also in barrels made of wood from autochthonous species [43, 45, 190], such as those specified in Table 1.  
As shown in Table 1, great variability exists in the coumarin contents of these kinds of wood, which has an impact on their concentrations in the spirits beverages aged with them (Tables 5-7). According to the findings of these research teams (Table 5), for the two kinds of wine spirits (_Armagnac_ and _Lourinha_), scopoletin is quantitatively the most important coumarin, followed by umbelliferone, which is in line with the contents found in the wood used in their ageing (Table 1). Scopoletin concentration is particularly high in wine spirits aged in oak barrels, especially those made with American and French species, which was also noted by [PERSON] et al. [22] in commercial spirits. Conversely, their levels are much lower in the wine spirits aged in chestnut barrels. Hence, these results support the hypothesis that scopoletin and umbelliferone act as chemical markers of oak wood. Low contents of aesculetin and 4-methylumbelliferone were quantified in _Armagnac_ spirits. However, [PERSON] et al. [22] recorded the presence of these compounds, as well as of fraxetin in higher concentrations in _Cognacs_. Such differences, as mentioned above, can be assigned to the variability of wood chemical composition and to the analytical methods. Interestingly, as far as we know, 4-methylumbelliferone was detected only in oak wood by [PERSON] et al. [22], although its content was not disclosed. Despite the extensive literature on brandies, including Brandy de Jerez, few studies have been devoted to analysing coumarins and their variation depending on ageing conditions, such as the type of wood used. The work of [PERSON] et al. [123] showed similar contents of scopoletin in Italian brandies aged in oak barrels from _Quercus robur_ and from _Quercus sessiliflora_ (Table 6). Considering that the raw material for producing wine spirit and brandy is the same (wine), it is interesting to compare the scopoletin content of the corresponding aged beverages. Regarding the wine spirits aged in _Q. robur_ wooden barrels (Table 4), a considerable difference in relation to _Armagnac_ is observed, while a similar concentration to that in the \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Origin** & **Wood Species** & **Compound** & **Mean Content (\(\mu\)g/L)** & **References** \\ \hline \multirow{4}{*}{Italy} & Oak & \multirow{2}{*}{scopoletin} & \multirow{2}{*}{102.1} & [123] \\  & _Q. robur_ & & & \\ \cline{1-1} \cline{2-5}  & Oak & & & \\ \cline{1-1} \cline{2-5}  & _Q. sessiliflora_ & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Coumarin contents in brandies according to the kind of wood used in their ageing.