## 3 Results
### Volatile Metabolites

Table 3: _Cont._  
\begin{table}
\begin{tabular}{l c c c c c c c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} \\ \hline \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} & \multicolumn{1}{c}{**Complete**} \\ \hline \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} \\ \hline \hline \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} & \multicolumn{1}{c}{**Taskboard**} \\ \hline \hline \multicolumn{1}{c}{**Taskboard**} & \As acetic acid did not show significant differences between the samples, this metabolite, associated with lactic acid bacterial metabolism [49], was not included in the volatile chemical classes of CSs. Quantitatively, the major chemical class present in all CS samples was furan derivatives (range 5815-23,431 ug/kg), exhibiting malty and sweet roasted aromas derived mainly from the degradation of carbohydrates [47]. A significantly higher content of fururans was found in light-roasted natural _Arabica_ CS than in all other CSs, with 2-pentyl furan, furfural, and 5-methyl-furfural being the most abundant. 2-Pentyl furan, a low-quality indicator in black defective coffee seeds [47], was rarely detected in the natural _Canephora_ CS. A heterocyclic component, 2-furanmethanol, which is formed by the degradation of sugars and quinic acid at high temperatures and is known to produce the bitter taste of roasted coffee [50], was mainly present in natural _Arabica_ CS samples after a higher temperature roasting treatment. Consequently, this bitter volatile marker seemed to be more susceptible to dry treatment and a high roasting temperature. The second-most detectable group of volatiles in the CS samples was the pyrrole group (2425-10,000 ug/kg), particularly in natural _Canephora_, mainly as a result of dark roasting. Pyroles are nitrogen-containing heterocycles produced by reactions between oxygen- and nitrogen-containing fragments [51] and antioxidant molecules formed through the Maillard reaction [52], with a peculiar sweet smell [47] and roasted or toasted flavours [32]. 1-Methylpyrrole, considered an off-flavour isolated from defective _Arabica_ roasted coffee [18], was the most detectable natural _Canephora_ dark-roasted CS. Pyrazines, the second-most abundant odour class in roasted coffee powder [53], were poorly detected in CS samples, in the range of 268-749 ug/kg. Natural _Arabica_ CS showed the highest content, whereas the lowest was in the washed _Arabica_ CS.