## 3 Results and Discussion
### Aroma Profiling  
A total of 81 flavor related compounds, with an accurate mass matching above 80%, were identified. Table 4 shows the identified chemical classes: pyrazines (2), alcohols (12), aldehydes (12), esters (9), ketones (2), terpenoids (37) of which (19 sesquiterpens and 17 terpenes), hydrocarbons (7) and other compounds (1). The chromatographic profiles (Figure 1) of different red _Topepo_ fruits showed wide differences in the peak areas of the main compounds and the amount distributions were different for each sample. Compared to CTR and to CV, the CO, treated red _Topepo_ fruits displayed a lower chromatographic complexity correlated to a lower intensity of the volatile fraction. In CTR, CO, and CV treated red _Topepo_ fruits, terpenoids (monoterpenes and sesquiterpenes) were the most abundant while in HD-grown RTSP, a similar concentration of alcohols (most representative family), terpenoids, and aldehydes was found. Despite the high number of detected volatile compounds, only some of them can be considered useful in the classification of red _Topepo_ aroma. In particular, between the identified compounds, 2-isobutyl-3-methoxypyrazine (green bell pepper), 2-sec-butyl-3-methoxypyrazine (carrot, lettuce, grassy), hexanal (grassy), nonenal (cucumber, herbal), 3-carene (red bell pepper, rubbery), \(\beta\)-ocimene (rancid, sweaty), (E) 4-nonanone, (E,Z) 2,6 nonadienal, (E,E) 2,4 decadienal are responsible for the green-related odor notes [61] and are the compounds identified at different extent in the different samples. The different concentrations drove the differences in the aromatic fingerprints. Methoxypyrazines, heterocyclic aromatic organic compounds naturally present in green plant tissue (in particular 2-isobutyl-3-methoxypyrazine and 2-sec-butyl-3-methoxypyrazine) were first identified in green capsicum (bell pepper), where they were found to be the principal compound responsible for the distinct capsicum odor. 2-isobutyl-3-methoxypyrazine, also known as _Grindstaff pyrazine_, confers to the fresh green bell peppers their distinctive smell and for this, is just called _bell pepper pyrazine_[62; 63; 64]. In short, both methoxypyrazines and 2-isobutyl-3-methoxyprazine can be considered quality markers of aromatic profile of our samples. Analysis of each profile and peak area showed that apart from the pyrazines, in all the samples analyzed, terpenes were the main compounds with large intra-class variations. In red _Topepo_ sweet pepper fruits treated with CV, the highest concentrations of pyrazines and terpenoids were found. Terpenoids are of great importance in determining the aromatic quality of vegetables and have a broad range of biological properties including cancer chemo preventive effects, antimicrobial, antifungal, antiviral, anti-hyperglycemic, anti-inflammatory, and anti-parasitic activity [65]. The aromatic fraction of sweet pepper fruits fertilized with CV was characterized both by the highest percentage of pyrazines and the highest concentration of terpenes, followed by esters and alcohols. A similar trend, although with lower percentages of terpenes in favor of aldehydes, was found in sweet pepper fruits grown with CO. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**ID** & **CTR** & **CO** & **CV** & **HD** \\ \hline DPPH & 60.67 b  & 70.67 b  & 84.33 a  \(\pm\) 5.15 \\ FRAP & 606.17 c  & 653.42 c  \(\pm\) 75.55 & 1304.84 a  & 809.49 b  \(\pm\) 168.74 \\ ABTS & 49.33 c  & 49.67 c  & 77.33 a  & 63.3 b  \\ FERROZINE & 25.00 b  & 24.00 d  & 57.00 a  & 14.00 c  \\ \hline \hline \end{tabular}  
* a, b, c d Letters show significant differences among the treatments (Tukey’s test. \(p\)-level \(\leq\) 0. 05).  
\end{table}