# Chemical Characterization of Cider Produced in Hardanger--From Juice to Finished Cider
## 3 Results and Discussion
### Volatile Compounds in Apple Juice and in Cider
The score plot in Figure 1 shows that 'Summerred' has a wide grouping at the top of the score plot, with higher levels of acetate esters (hexyl acetate and isoamyl acetate) and ethyl esters of aliphatic acid (ethyl hexanoate, ethyl octanoate, ethyl decanoate, and ethyl butyrate). Also, some 'Aroma' samples have high levels of these esters. In contrast, 'Gravenstein' and 'Discovery' showed sample clusters in the middle/lower part of the PCA plot with higher levels of hexanol and ethyl isovalerate. One explanation for these wide groupings could be the nitrogen availability from amino acids for the yeasts. Only a few of the cider producers added nitrogen supplements to support fermentation. Nitrogen content and the amino acid profile, which is mainly composed of asparagine, aspartic acid, glutamic acid, proline, and serine in apples [33], are important for ester formations during fermentation [34]. Esters and nitrogen will be a topic for future cider research. \begin{table}
\begin{tabular}{c c c c c c} \hline  & & & **Juice (mg L\({}^{-1}\))** & & **Cider (mg L\({}^{-1}\))** \\ \hline
**Parameter** & **Variety** & **N** & **Mean (Min-Max)** & **N** & **Mean (Min-Max)** \\ \hline \multirow{4}{*}{Octyl acetate} & Aroma & 5 & 5.06 (0.30–12.2) & 7 & 1.04 (0.30–2.20) \\  & Discovery & 3 & 6.80 (2.60–15.2) & 3 & 1.40 (0.80–2.30) \\  & Gravenstein & 5 & 0.64 (0.10–1.10) & 3 & 1.27 (0.90–1.90) \\  & Summerred & 4 & 0.48 (0.20–0.60) & 4 & 1.25 (1.00–1.70) \\ \hline \multicolumn{5}{c}{Ethyl Esters of hydroxycimamic acid} \\ \hline \multirow{4}{*}{Ethyl cinnamate} & Aroma & 5 & 0.76 (0.40–1.50) & 7 & 0.84 (0.40–1.60) \\  & Discovery & 3 & 0.73 (0.40–1.30) & 3 & 0.63 (0.40–0.80) \\  & Gravenstein & 5 & 0.60 (0.10–1.10) & 3 & 1.03 (0.30–2.10) \\  & Summerred & 4 & 0.50 (0.40–0.60) & 4 & 4.47 (0.30–11.6) \\ \hline \multirow{4}{*}{Ethyl dihydrocinnamate} & Aroma & 5 & 0.22 (0.20–0.30) & 7 & 0.37 (ND–1.10) \\  & Discovery & 3 & 0.20 (ND–0.40) & 3 & 0.10 (0.10–0.10) \\  & Gravenstein & 5 & 0.16 (ND–0.40) & 3 & 0.43 (0.10–0.90) \\  & Summerred & 4 & 0.08 (ND–0.30) & 4 & 0.60 (0.10–1.80) \\ \hline \multicolumn{5}{c}{C6-Alcohols} \\ \hline \multirow{4}{*}{Hexanol} & Aroma & 5 & **15,778 (2895–33,297)** & 7 & 7799 (4602–12,850) \\  & Discovery & 3 & **13,441 (2556–27,675)** & 3 & **10,022 (6958–11,849)** \\  & Gravenstein & 5 & **15,380 (6166–28,187)** & 3 & **11,655 (6824–20,464)** \\  & Summerred & 4 & **9101 (1752–24,950)** & 4 & **8183 (6963–9490)** \\ \hline \multirow{4}{*}{Z-3-hexenol} & Aroma & 5 & 142 (7.60–272) & 7 & 80.8 (10.2–187) \\  & Discovery & 3 & 29.5 (11.6–42.2) & 3 & 31.9 (17.8–48.3) \\  & Gravenstein & 5 & 78.4 (11.7–164) & 3 & 58.6 (15.4–106) \\  & Summerred & 4 & 32.9 (5.60–97.1) & 4 & 34.9 (26.9–39.1) \\ \hline \multirow{4}{*}{E-2 hexenol} & Aroma & 5 & 648 (84.0–1839) & 7 & 6.57 (ND–14.5) \\  & Discovery & 3 & 1267 (67.0–2059) & 3 & 13.4 (5.60–21.6) \\ \cline{1-1}  & Gravenstein & 5 & 634 (75.0–1717) & 3 & 13.4 (8.70–17.8) \\ \cline{1-1}  & Summerred & 4 & 552 (188–1207) & 4 & 10.4 (7.70–14.7) \\ \hline \multirow{4}{*}{E-3 hexenol} & Aroma & 5 & 19.8 (ND–37.6) & 7 & 23.1 (6.80–56.8) \\ \cline{1-1}  & Discovery & 3 & 25.8 (4.80–62.5) & 3 & 35.6 (21.8–51.8) \\ \cline{1-1}  & Gravenstein & 5 & 18.1 (4.80–32.1) & 3 & 36.0 (11.5–50.4) \\ \cline{1-1}  & Summerred & 4 & 11.5 (1.90–26.6) & 4 & 37.4 (28.4–57.8) \\ \hline \end{tabular}
\end{table} 
Table 4: _Cont._The quantitative headspace results for the esters and C6-alcohols are presented in Table 4. In the juice and ciders of the cultivar 'Aroma', 'Discovery', 'Gravenstein', and 'Summerred', the ethyl esters of aliphatic acids ethyl butyrate, ethyl hexanoate, and ethyl octanoate, and the ethyl esters of branched fatty acids isovalerate and ethyl 2-methylbutyrate, were in concentrations over the odour threshold limit (Tables 4 and S5). 'Aroma' and 'Discovery' juice and ciders had butyl acetate concentrations above the threshold limit.