## 3 Discussion
### Other Compounds  
In this heterogeneous group, we collected the residual analytes, which did not seem to be related to the compounds identified and previously classified according to their molecular structure and functional groups. Even though some molecules such as methoxyphenyl-oxime, pyrrole and pyranone, as well as epoxybutyrate, were detected in our samples and in other fruits, there was a lack of information on the chemical and biochemical cycles that rationalize their presence in nature. Finally, it is worth noting that for propylene glycol, identified in the M_AI_V_t\({}_{0}\) sample (Table 1), we did not find mention of _Cucurbitaceae_ fruits in the specific literature. Table 4 summarizes the results obtained from the HS-SPME-GC-MS analysis for the different fibrous samples from winter melon pomace, collected in comparative form based on the classes of compounds identified. A one-way analysis of variance (ANOVA) was performed to assess whether there was a statistically significant difference between the quantities of each compound class among the M_AI_V_t\({}_{0}\), M_B_O_t\({}_{0}\), and M_B_O_t\({}_{24}\) samples. The \(p\)-value, for almost all the investigated compounds, excluded AHA and OTH groups, was smaller than the significance level (0.05). So, we can conclude that, globally, the investigated DF samples are statistically different. For clarity, Figure 7 summarizes the results obtained from the HS-SPME-GC-MS analysis for the different fibrous samples of the winter melon pulp, grouped comparatively according to the classes of the identified compounds. The fibers obtained after the bleaching process with H\({}_{2}\)O\({}_{2}\) at t\({}_{0}\) time (M_B_O_t\({}_{0}\)) and the sample stored for 24 months (M_B_O_t\({}_{24}\)) presented an HS composition significantly different from that of the \"As-it-Is\", vacuum-freeze-dried pomace fiber (M_AI_V_t\({}_{0}\)). In particular, some specific considerations can be developed for some classes of molecules, listed in Table 4 and Figure 8. \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Compound Class**} & **M\_AI\_V\_t\({}_{0}\)** & **M\_B\_O\_t\({}_{0}\)** & **M\_B\_O\_t\({}_{24}\)** & **\(p\)-Value** \\ \cline{2-5}  & \(\mathbf{-}^{*}\) & \(\mathbf{-}^{*}\) & \(\mathbf{x}\)\(\mathbf{\pm}\)\(\mathbf{s_{(3)}}\) & \(\mathbf{x}\)\(\mathbf{\pm}\)\(\mathbf{s_{(3)}}\) & \\ \hline ALC (alcohols) & 33.8 \(\pm\) 3.2 & 12.3 \(\pm\) 2.3 & 7.3 \(\pm\) 0.9 & \(p\) \(<\) 0.05 \\ \hline ALD (aldehydes) & 24.7 \(\pm\) 2.4 & 33.2 \(\pm\) 3.9 & 29.5 \(\pm\) 2.7 & \(p\) \(<\) 0.05 \\ \hline KET (ketones) & 14.5 \(\pm\) 2.6 & 12.5 \(\pm\) 2.2 & 5.9 \(\pm\) 0.8 & \(p\) \(<\) 0.05 \\ \hline ACD (acids) & 9.7 \(\pm\) 1.7 & 33.8 \(\pm\) 3.7 & 57.3 \(\pm\) 4.4 & \(p\) \(<\) 0.05 \\ \hline ACE (acetate esters) & 7.2 \(\pm\) 1.0 & — & — & \\ \hline SDC (sulfur compounds) & 4.7 \(\pm\) 0.8 & — & — & \\ \hline NAE (non-acetate esters) & 3.0 \(\pm\) 0.6 & 6.1 \(\pm\) 0.7 & — & \(p\) \(<\) 0.05 \\ \hline AHA (alkanes) & 0.2 \(\pm\) 0.2 & 0.6 \(\pm\) 0.4 & — & \(p\) \(>\) 0.05 \\ \hline OTH (other compounds) & 2.2 \(\pm\) 0.5 & 1.4 \(\pm\) 0.9 & — & \(p\) \(>\) 0.05 \\ \hline \end{tabular}  
* Data are expressed as mean % of each class to the total normalized peak areas on the basis of the sum of the TIC area.
* Mean of three replicates of the chromatograms \(\pm\) standard deviation \(s_{(3)}\).  
\end{table} 
Table 4: Compound classes identified in the HS-SPME-GC-MS analysis * of the fiber samples obtained from winter melon pomace. 1. Volatile compounds typical of the ripe fruit (alcohols, esters): Alcohols covered about one third of the VOCs of the M_AI_V_t0 fiber, while immediately after the bleaching treatment, they represented \(\approx\)12 % of the volatiles (M_B_O_t0) and only \(\approx\)7 % in the aged sample (M_B_O_t24). Acetate esters were present only in the M_AI_V_t0 sample at a relative percentage of about 7 %, and completely disappeared in the treated ones.