## 3 Results
### Volatile Metabolites
Thus, natural and washed _Canephora_ CS and washed _Arabica_ CS were poorly represented by all these compounds present at low concentrations. Findings on furans showed that 5-methyl-furfural may differentiate _Arabica_ from _Canephora_ CS species and separate the post-harvest treatments, becoming a possible CS post-harvest technological marker owing to its higher content in natural _Arabica_ CS than in washed _Arabica_ or _Canephora_ CSs. Conversely, in natural _Canephora_ CS samples, higher amounts of alkyl pyrroles and sulphur compounds (dimethyl di- and tri-sulphide and thiophene) were detected, in contrast to the natural _Arabica_ CS. Accordingly to [PERSON] et al. [31], sulphur molecules appeared to increase in coffee during overroasting. However, the 2-furfurylthiol, found in the _Arabica_ coffee after the low-temperature roasting process [31], was not detected in the CS samples. Two di-sostituite alchyl pyrazines (2,5- and 2,6-dimethyl-pyrazine) were abundant in washed _Canephora_ CS. The aroma of natural _Canephora_ CS was characterised by higher amounts of pyridines and a phenolic compound with a spicy odour (4-vinyl guaiacol) derived from chlorogenic acid (CGA), as reported in _Canephora_[2; 29] and _Arabica_[45] coffee. Heterocyclic azotate compounds from the degradation of trigonelline (pyridine and N-methylpyroles) were also present in the volatile fraction of the CSs. These compounds are produced in a model reaction system of the classic Maillard reaction. Pyridines are more abundant in natural _Canephora_ CS, and are responsible for bitter, asrtingent, roasted, and burnt notes [46; 47]. Finally, a high quantity of 2-furanmethanol, a volatile antioxidant heterocyclic compound [48], was detected in natural _Arabica_ CS. To better highlight the differences between samples, the volatile compounds were clustered into 10 chemical classes (Table 4). \begin{table}
\begin{tabular}{l r r r r r} \hline \hline  & \multicolumn{4}{c}{**Natural**} \\ \cline{2-6}  & \multicolumn{2}{c}{_Canephora_} & \multicolumn{2}{c}{_Arabica_} \\ \cline{2-6}  & **Light** & **Medium** & **Dark** & **Light** & **Medium** & **Dark** \\ \hline
**Aldehydes** & & & & & \\ hexanal & 1404.66 \(\pm\) 157.54 & 1542.63 \(\pm\) 415.42 & 1135.25 \(\pm\) 23.8 & 2697.24 \(\pm\) 134.52 & 2184.86 \(\pm\) 194.80 & 2046.37 \(\pm\) 93.57 \\ heptanal & 258.11 \(\pm\) 18.91 & 220.06 \(\pm\) 36.25 & 245.03 \(\pm\) 14.95 & 390.72 \(\pm\) 37.22 & 366.24 \(\pm\) 25.48 & 286.95 \(\pm\) 4.46 \\ benzaldehyde & 1478.76 \(\pm\) 239.36 & 1245.71 \(\pm\) 271.55 & 1750.03 \(\pm\) 152.18 & 1218.69 \(\pm\) 112.61 & 1127.80 \(\pm\) 72.58 & 913.87 \(\pm\) 27.75 \\ \(\beta\)-methyl- & 40.35 \(\pm\) 10.99 & 41.05 \(\pm\) 16.33 & 35.95 \(\pm\) 2.62 & 188.57 \(\pm\) 2.12 & 175.46 \(\pm\) 6.04 & 144.22 \(\pm\) 2.58 \\ benzaneacetaldehyde & 405.63 \(\pm\) 35.14 & 362.11 \(\pm\) 146.94 & 449.94 \(\pm\) 115.47 & 362.33 \(\pm\) 37.43 & 377.68 \(\pm\) 42.45 & 274.43 \(\pm\) 23.11 \\
**Alebols** & & & & & \\ 2-heptanol & 179.24 \(\pm\) 25.96 & 186.66 \(\pm\) 50.79 & 220.39 \(\pm\) 24.45 & 2433.20 \(\pm\) 134.42 & 2237.48 \(\pm\) 85.04 & 1737.06 \(\pm\) 27.84 \\
1-hexanol & 40.60 \(\pm\) 5.96 & 43.53 \(\pm\) 5.64 & 46.54 \(\pm\) 4.95 & 280.05 \(\pm\) 31.09 & 254.36 \(\pm\) 7.20 & 191.38 \(\pm\) 2.61 \\ \(\beta\)-butoxy-ethanol & 289.55 \(\pm\) 111.57 & 172.12 \(\pm\) 114.19 & 952.12 \(\pm\) 10.19 & 330.91 \(\pm\) 357.52 & 207.12 \(\pm\) 76.78 & 316.65 \(\pm\) 150.32 \\ phenylethyl alcohol & 181.34 \(\pm\) 70.42 & 226.23 \(\pm\) 187.68 & 161.26 \(\pm\) 45.50 & 480.88 \(\pm\) 53.66 & 525.13 \(\pm\) 42.63 & 468.86 \(\pm\) 48.14 \\
**Indole** & & & & & \\ 5-hydroxy-1H-indole \({}^{\lx@sectionsign}\) & 42.80 \(\pm\) 10.12 & 41.71 \(\pm\) 9.24 & 56.07 \(\pm\) 6.17 & 88.87 \(\pm\) 0.39 & 87.76 \(\pm\) 5.40 & 77.47 \(\pm\) 0.76 \\ \hline \hline \end{tabular}  
\({}^{\lx@sectionsign}\): Tentative identification performed only by mass spectral matching against NIST 05 MS library; ND—not detected.  
\end{table}