# The Impact of Terroir on the Flavour of Single Malt Whisk(e)y New Make Spirit
## 3 Results
### Aroma Active Compounds
#### 3.1.6 Grassy and Vegetal Odours  
Three unknown compounds had high MF values within this category (Table 1). Unknown compound 10 (herbal/grass) had a very high contribution to the aroma of new make spirits based on its average MF value of 93.5%. Unknown compound 6 had an average MF value of 61.8% and was characterised by a cut grass/green-bell pepper aroma. The MF% values of the unknown compounds 6 and 10 were not impacted by season, variety, or environment. Unknown compound 9 with a grass aroma had a lower average MF value of 58.9% and was impacted by environment (higher at Athy) (Tables 1 and 2).  
Five aldehydes methional, heptanal, (E) 2-octenal, hexanal, and decanal were included in this category based on their aromas (Table 1). Methional belongs to the category of vegetal odours and is derived from methionine through Strecker degradation reactions. It was described as having a boiled potato odour and had a great significance on the overall aromatic profile with an average MF of 80.9%. Methional aroma intensity was impacted by season and environment (highest in 2017 and at Athy) (Tables 1 and 2). In a previous study, methional was reported to have a negative impact on Spanish wine aroma by masking their fruity character [51]. However, as it has a very low odour threshold [24; 42], it is an important compound even though potentially negatively impacting on aroma. Methional is also likely a precursor for dimethyl disulfide and dimethyl trisulfide in whisk(e)y [52], which are both problematic sulphur compounds that can carry over from distillation into the new make spirit. Heptanal had a seaweed/grass/rubber aroma and has previously been detected at trace levels in barley and malt for beer production [4]. The average MF values was 69.5% and the intensity was impacted by season and variety (highest in 2017 and Olympus) (Tables 1 and 2). It is not a common compound in distilled spirits. The remaining aldehydes within this category had MF values <50% and therefore were less likely to be impactful aroma compounds. (E)-2-Octenal was characterised as having a vegetable/cabbage aroma but had a low average MF of 37%. (E)-2-octenal has been detected in barley [35] and along with (E)-2-nonenal and 1-decanal was associated with the sawdust character of wines aged in new make barrels [31]. The intensity was not impacted by season, variety, or environment. Hexanal had a characteristic green/vegetative odour and an average MF of 32.2%, and its intensity was impacted by variety (higher in Olympus). Hexanal is considered a key odorant in barley and malt and can be impacted by the malting process [4], fermentation conditions [53], and the distillation process [54]. The average MF value of decanal (grass/lemon) was 30.9%, and its value was not impacted by season, variety, or environment. It has been detected at trace levels in barley and malt for beer production [4].  
The remaining volatile in this category is citronelly! acetate* (fresh/green) (only tentatively identified), which is an ester of a monoterpene citronellol likely derived directly from the barley. It is possible that the ester is formed during fermentation when the citronellol comes in contact with acetic acid. Its average MF value was 44.8%, but it was not impacted by season, variety, or environment. It is not a common compound in distilled spirits.