## 2 Results
### PTR-ToF-MS: Determination of Volatile Compounds from Hop Dried Leaves  
Hop-dried leaf samples analyzed by a Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS) were prepared in the same way as the ones used for Solid Phase Microextraction/Gas Chromatography-Mass Spectrometry (SPME/GC-MS) analysis with the aim to compare the results of these two methodologies. The PTR-ToF-MS data were filtered following the procedure previously described by [PERSON] et al. (2015). Thus, all peaks imputable to water chemistry and all the interfering ions (e.g., oxygen, nitrogen monoxide) were eliminated, and subsequently, the peaks whose average concentrations were lower than 0.5 ppbv (parts per billion by volume) were also eliminated. After filtering the whole volatile organic compounds (VOCs), the spectra of the hop-dried leaf (analyzed in triplicate) were composed of 25 VOCs with different emission intensities, as reported in Table 2. All these detected compounds were identified up to \(m/z\) 205.195, and no other compounds with higher molecular weight were identified with an emission intensity greater than 0.5 ppbv. The revealed compounds could be tentatively attributed to compounds such as aldehydes, ketones, alcohols, terpenes, and sulfur compounds (Table 2 and the identifiers were also reported (Table S2)). The highest hop leaves volatile emissions were detected for the compounds detected at \(m/z\) 59.059 and 45.033, which showed, as a sum, over 60% of the total emission. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \(\mathbf{N}^{\circ}\) & **COMPONENT 1** & **LRI 2** & **LRI 3** & **Chinook (\%)** \\ \hline
16 & \(\gamma\)-cadinene & 1510 & 1509 & 2.2 \(\pm\) 0.02 \\
17 & \(\delta\)-cadinene & 1513 & 1505 § & 5.7 \(\pm\) 0.03 \\
18 & selina-3,7(11)-diene & 1535 & 1530 & 0.4 \(\pm\) 0.01 \\ \hline  & SUM & & 100.0 \\  & Monoterpenes & & 0.4 \\  & Diterpenes & & 0.4 \\  & Sesquiterpenes & & 85.8 \\  & Others & & 13.4 \\ \hline \hline \end{tabular}  
* The components are reported according to their elution order on apolar column (VF-1 ms); 2 Linear Retention Indices measured on apolar column; 3 Linear Retention Indices from literature; § Normal alkane RI.  
\end{table} 
Table 1: _Cont._ \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \(\mathbf{N}^{\circ}\) **of** & \multirow{2}{*}{\(m/z\)} & **Chemical** & **Average** & **Standard** & **Emission** \\
**Compounds** & & **Formula** & **Samples** & **Decision** & **(\%)** \\ \hline
1 & 27.022 & C\({}_{2}\)H\({}_{3}\)\({}^{+}\) & Acetylene & 21.82 & 2.60 & 3.03 \\
2 & 31.018 & CH\({}_{3}\)O\({}^{+}\) & Formaldehyde & 50.21 & 4.64 & 6.96 \\
3 & 33.033 & CH\({}_{3}\)O\({}^{+}\) & Methanol & 22.79 & 3.95 & 3.16 \\
4 & 41.038 & C\({}_{3}\)H\({}_{5}\)\({}^{+}\) & Alkylic fragment & 11.69 & 2.16 & 1.62 \\
5 & 43.018 & C\({}_{2}\)H\({}_{3}\)O\({}^{+}\) & Aldehyde fragment & 31.53 & 10.18 & 4.37 \\
6 & 43.054 & C\({}_{3}\)H\({}_{7}\)\({}^{+}\) & General alkane/VOC fragment & 26.83 & 4.17 & 3.72 \\
7 & 45.033 & C\({}_{2}\)H\({}_{5}\)O\({}^{+}\) & Acetaldehyde & 229.17 & 61.98 & 31.79 \\
8 & 47.013 & CH\({}_{3}\)O\({}_{2}\)\({}^{+}\) & Formic acid/formates & 9.19 & 1.34 & 1.27 \\
9 & 49.011 & CH\({}_{5}\)S\({}^{+}\) & S Compound (methanethiol) & 1.45 & 0.21 & 0.20 \\
10 & 55.054 & C\({}_{4}\)H\({}^{+}\) & Fragment & 7.12 & 1.44 & 0.99 \\
11 & 57.069 & C\({}_{4}\)H\({}_{9}\)\({}^{+}\) & Alcohol fragment & 3.58 & 0.78 & 0.50 \\
12 & 59.049 & C\({}_{3}\)H\({}_{7}\)O\({}^{+}\) & Propanal, Acetone & 236.97 & 52.32 & 32.87 \\
13 & 61.028 & C\({}_{2}\)H\({}_{5}\)O\({}_{2}\)\({}^{+}\) & Acetates & 21.72 & 3.61 & 3.01 \\
14 & 69.069 & C\({}_{5}\)H\({}_{9}\)\({}^{+}\) & Isoprene/Cycloalkane fragment & 5.87 & 1.39 & 0.81 \\
15 & 71.049 & C\({}_{4}\)H\({}_{7}\)O\({}^{+}\) & Butenal & 1.7 & 0.41 & 0.24 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Chemical composition (mass charge, chemical formula, tentative identification, average emission, standard deviation, percentage emission for each \(m/z\) detected) of \(H\).