# The Impact of Terroir on the Flavour of Single Malt Whisk(e)y New Make Spirit
## 3 Results
### Aroma Active Compounds
#### 3.1.3 Fatty Odours  
Fatty aromas in these samples were due to aldehydes and alcohols (Table 1). The most important compounds in the category were (E)-2-nonenal (fried/toasted/fatty), 3-methyl-1-butanol (fermented/yeast/rancid), and 3-methylbutanal (butter/cheese/chocolate). (E)-2-Nonenal is generated through lipid oxidation of linoleic and linolenic acid during the malting process (4; 15) and from wood during maturation (31), but it has also been detected  
\begin{table}
\begin{tabular}{l l l l l l l l} \hline
**Compound** & **Attribute** & **Odour** & \multicolumn{2}{c}{**Variety MF\%**} & \multicolumn{2}{c}{**Environment MF\%**} & \multicolumn{2}{c}{**Season MF\%**} \\ \cline{5-8}  & & **Type** & **Laureate** & **Olympus** & **Athy** & **Bunclody** & **2017** & **2018** \\ \hline
1-Octen-3-one & metallic/mineral/mushroom & earthy & 72.4 1  & 72.7 2 [FOOTNOTE:2]Footnote 2: \(\mathrm{b}^{,}\mathrm{a}^{,}\mathrm{b}^{,}\mathrm{b}^{,}\mathrm{a}^{,}\mathrm{b}^{,} \mathrm{  
at trace levels in barley [4; 32]. (E)-2-Nonenal was found to contribute to the green notes of Scotch malt whisky [33], and it was identified as a significant compound for new make and aged Bourbon aroma [9; 16]. However, [PERSON] et al. (2019) has also linked high concentrations of (E)-2-nonenal to unpleasant aromas [9]. The high average MF values for these three compounds (E)-2-nonenal, 3-methyl-1-butanol and 3-methylbutanal at 94.2%, 87.1% and 60%, respectively reflect their significant importance to the aroma of new make spirits (Table 1). The MF% (E)-2-nonenal intensity was impacted by environment (higher at Athy) (Tables 1 and 2). The chemical pathways for the formation of 3-methylbutanal and 3-methyl-1-butanol are similar [5]. 3-Methylbutanal is derived from the amino acid leucine and is a characteristic volatile compound in some dessert wines [34]. It is considered as an active odour compound of brewing barley [35] and of aged bourbon [15], where the odour was described as malty. [PERSON] et al. (2013) [4] observed that the malting and fermentation processes impacted on aldehydes and that a significant formation of 3-methylbutanal occurred during the roasting process. The MF% of 3-methylbutanal was not impacted by season, variety, or environment. The alcohol 3-methyl-1-butanol has a lower odour threshold compared to its precursor (3-methyl-butanal) and is frequently found in alcoholic beverages [7; 16; 17; 36; 37]. The concentration of 3-methyl-1-butanol in relation to other major volatile compounds has being proposed for the authentication of Scotch and Irish whisk(e)y [38]. It is mainly produced during fermentation and is affected by the fermentation conditions [39]. At high concentrations, 3-methyl-1-butanol can confer an undesirable aroma, but it has been described as burnt/whisk(e)y [40], malty/rancid/pungent [26], plastic [6], and chocolate [17]. 3-Methyl-1-butanol was described as having a fermented/yeast/rancid odour in this study, but MF% was not impacted by season, variety, or environment.  
2-Methylbutanol (rancid/buttermilk) had an average MF of 47.9%, and it was not influenced by season, variety, or environment. 2-Methyl butanol content has been previously used with 3-methyl-butanol to authenticate Scotch whisky [41]. 2-Methyl-1-propanol (butter/baked) is also an important volatile contributing to the flavour of whisk(e)y; it is formed during fermentation, and its production can be affected by the choice of yeast strain [42]. 2-Methylpropanol also known as isobutanol had an average MF value of 40.9% and was not impacted by season, variety, or environment. 2-Methylpropanal (butter/rancid) also known as isobutyraldehyde had a much lower average MF at 16.8% and therefore of much less importance and was not influenced by environment, variety, or season (Tables 1 and 2). 2-Methylpropanal is predominately produced during fermentation and has been associated with unpleasant tastes in spirits [43].