## 3 Results and Discussion
### Higher Alcohol and Ester Analysis
Ethyl butanoate (fruity [24]) and ethyl hexanoate (green apple, brandy, fruity [24]) were present in the apple juice, but their concentrations increased by 26% and 38%, respectively, by day 12 of fermentation. Similarly, hexyl acetate (fruity, sweet [30]), ethyl octanoate (fruity, candy, pineapple [11]), and ethyl decanoate (brandy, fruity [24]), which were not detected in the juice, were established as major species within the headspace by fermentation day 12. Maximum concentrations of ethyl hexanoate (0.224 \(\pm\) 0.021 mg L\({}^{-1}\)) and hexyl acetate (0.763 \(\pm\) 0.05 mg L\({}^{-1}\)) during the fermentation phase were observed on day 22. Before the ciders were cold crashed and racked on day 25 (marked in Figure 4 with a vertical black line), ethyl octanoate and ethyl decanoate reached fermentation concentration maxima of 0.55 \(\pm\) 0.12 mg L\({}^{-1}\) and 0.55 \(\pm\) 0.124 mg L\({}^{-1}\), which are above or within error of the published perception thresholds for these species [11]. All five esters experienced a sizeable decrease to minimum concentrations following the racking event on day 25. On day 40, ethyl butanoate, ethyl octanoate, and ethyl decanoate had diminished by 69%, 33%, and 71%, respectively. Ethyl hexanoate and hexyl acetate decreased by 33% and 67% from their maximum concentrations by day 47. HS-SPME-GC-MS analysis was conducted again at the end of maturation on day 135. At the end of maturation, ester concentrations increased, most notably ethyl octanoate and ethyl decanoate. This experimental evidence supports previous observations of ester growth when cider is held over yeast lees for extended periods of time. All five of these esters have a predominately fruity aroma and were all detected above perception thresholds and likely contribute pleasant fruity notes to the ciders [14]. The development and changes in four higher alcohols are shown in Figure 4B. 1-Pentanol (balsamic, fruity [24]) coelutes with two other species (3-methyl-1-butanol and 2-methyl-1-butanol) that were not baseline resolved with our GC method. The integrated peak area of the three chromatographic peaks were summed and reported together as 1-pentanol. These species together were quantified to be, perhaps unsurprisingly, at the highest concentration of any other analyte observed in this study. 1-pentanol and 2-methyl-1-butanol were both detected in the juice, whereas 3-methyl-1-butanol was first detected within the first 12 days of fermentation indicating the possibility of either isomerization or the development of a new fermentation byproduct. Better separation of the species could be achieved by beginning the separation at a lower temperature (\(<\)50 \({}^{\circ}\)C) or slowing the temperature ramping. Trends for the four higher alcohols monitored over the 135-day process were much more varied than the esters. 1-Hexanol (green, herbaceous [24]) was the predominant alcohol in the juice and two days after fermentation had increased in concentration by 56%. Interestingly, by day 12, 1-hexanol decreased by 42%. From day 12 to the end of maturation (day 135), 1-hexanol concentration decreased another 19%, but maintained its position as the second most abundant higher alcohol. 1-Butanol remained relatively constant throughout the 135-day process, at a concentration considerably below the perception threshold. 2-Phenylethyl alcohol (floral, honey-like [11; 14]) was not present in the juice but was the third most abundant higher alcohol by the end of maturation. Although a rise was observed for many higher alcohols after cracking (day 25), the alcoholic and floral aroma imparted by these species remained steady once the specific gravity reached levels close to 1.001 (day 47).