# The Impact of Terroir on the Flavour of Single Malt Whisk(e)y New Make Spirit
## 3 Results
### Aroma Active Compounds
#### 3.1.5. Fruity Odours  
Eleven volatiles were grouped in this category (Table 1). The fruity aromas of new make spirits were due to esters and some acetals, and the most representative compounds of these categories were ethyl hexanoate, which is an unknown compound (unknown compound 8), 1,1-diethoxy-2-methyl-propane* (tentatively identified), ethyl isobutyrate, 3-methylbutyl acetate (also known as isoamyl acetate), 1,1-diethoxyethane, ethyl butyrate, and ethyl-3-methylbutyrate as their average MF was \(>\)50%.  
The average MF value of ethyl hexanoate (pear/fruity) was 84.9%, indicating its significant contribution to the aroma of new make spirit, and it was not impacted by season, variety, or environment (Tables 1 and 2). Ethyl hexanoate is a fatty acid ethyl ester produced during fermentation by a combination of ethanol and hexanoic acid, and it has been previously identified as a major aromatic compound of new make and aged bourbon [9; 16], and an important compound in other alcoholic beverages [6; 17; 46]. In red wines, ethyl hexanoate confers a red-berry aroma [47] and is known to enhance fruity notes in grape spirits [17]. The unknown compound 8 also had a high average MF at 84.2%, indicating its potential significance to the aroma of new make spirit. Unknown compound 8 has the aroma of lemon/cleaning fluid, and its MF% was influenced by season (higher in 2018). Another ester that contributed to the fruity aroma of the new make spirit samples was 3-methylbutyl acetate (isoamyl acetate) with the characteristic odour of banana/fruity/melon with an average MF of 70.4%. The MF% was not impacted by season, variety, or environment. It has been previously identified in distillates [6; 17; 15] and is produced from a combination of 3-methyl-1-butanol and acetic acid. Ethyl isobutyrate (also known as ethyl 2-methylpropanoate) (fruity/sweet/cherry) formed from ethanol and isobutyric acid (2-methylpropanoic acid) had an average MF of 62.7% and was influenced by season (higher in 2017) (Tables 1 and 2). Ethyl isobutyrate has been previously identified as important volatile in bourbon [16]. Ethyl butyrate (fruity/apples) also had a high average MF of 57.8% and was impacted by season and environment (higher in 2017 and Bunclody) (Tables 1 and 2). Ethyl butyrate is commonly found in a wide range of spirits and is produced from ethanol and butyric acid during fermentation. Another ester ethyl-3-methylbutyrate (pineapple/apples) (also known as ethyl isovalerate) had an average MF of 54% and was impacted by season (higher in 2017). It is also an important odour compound in bourbon [16]. Two other esters were also aroma active but had MF values \(<\) 50% and therefore are less important. These again are products primarily of fermentation and are derived from their corresponding alcohols and acids. Ethyl decanoate (grape/apple/waxy) had an average MF of 39.5% and propyl acetate (pear/fruity) had an average MF of 20.3%. Both were not impacted by season, variety, or environment (Tables 1 and 2). Ethyl decanoate has been previously found in whisk(e)y [7; 48] and propyl acetate has been previously found in calvados [6] and cognac [17].  
The acetals, 1,1-diethoxy-2-methyl-propane* (tentative identification) and 1,1-diethoxyethane, conferred fruity notes. The average MF values for 1,1-diethoxy-2-methyl-propane* and 1,1-diethoxyethane were 72.1 and 59.4%, respectively, and they were not influenced by season, environment, or variety. Acetals are characterised with more pleasant aromas (fruity/apple/pineapple/cherry) compared to their aldehyde precursors (pungent), and they are formed during distillation and are known to be significantly impacted by distillation conditions [17; 49; 50]. Another unknown compound (unknown compound 3)had a low average MF% of 24.1% and therefore is of less importance. It was characterised by a fruity/butter aroma and was impacted by variety (higher in Olympus) (Tables 1 and 2).