## 3 Results and Discussion
### Profile in VOCs
#### 3.1.2 Group of Isothiocyanates  
Overall, seven different ITCs were identified in the present work among the evaluated wall rocket materials (Table 3). Allyl ITC (I1) was reported as the main sulfurous compound in this chemical group and was also the main VOC in the total profile of the species (Table 4). Additionally, other ITCS were identified and included 3-butenyl ITC (I2), 3-methylbutyl ITC (I3) and benzyl ITC (I6), together with hexyl ITC (I5), phenylethyl ITC (I7) and pentyl ITC (I4), which often showed the lowest levels (Table 4). In agreement with our results, these compounds have been previously described in wall rocket microgreens and seedlings [4]. By contrast, for mature leaves, stems and pods, [PERSON] et al. [33] only identified allyl ITC, 3-butenyl ITC and phenylethyl ITC. The presence and relative contribution of individual ITCs in wall rocket differs considerably to those reported in the rocket crops [11; 22; 26; 29; 34; 35; 36; 37; 38; 39; 40]. Thus, three compounds identified in the present study for wall rocket (i.e., allyl ITC, benzyl ITC and phenylethyl ITC) were not reported in the literature for the related rocket crops (Table S1). Similarly, other sulfur-containing compounds described in both salad and wild rocket were not found in our wall rocket materials. Since individual ITCs have been described to add specific sensory descriptors [13], differences in the ITCs fraction (both qualitative and relative abundances) can result in remarkable differences in flavor. In this context, we hypothesize that wall rocket should be marketed as a new crop, as its aroma is not greatly correlated to rocket crops [4]. In fact, previous works evaluating the sensory attributes and consumers acceptance suggest that comparing wall rocket with the commercial rocket crops may increase consumers rejection [3] as the species would show an unexpected, no rocket-like flavor. On the contrary, the volatile profile of wall rocket could be more related to other _Brassicaceae_ crops such as wasabi, mustard or horseradish. For all these crops, allyl ITC has been described as the predominant ITC [4; 41; 42; 43]. Providing characteristic flavor notes that are described as pungent, sulfurous, bitter, lachrymose and mustard-, onion- and wasabi-like [13; 42], this compound would be greatly responsible of the common pungent notes that all these crops show. In addition, 3-butenyl ITC, 3-methylbutyl ITC and phenylethyl ITC have been also described in the volatile profile of horseradish and mustard, the former crop highlighting for the content in phenylethyl ITC as second predominant ITC [4; 42]. By contrast, phenylethyl ITC has not been reported in wasabi tissues [44; 45] although it can be found in wasabi-based products [4]. Regarding the comparison of the ITCs fraction in the populations of wall rocket, it was found that most materials showed similar profiles in qualitative terms but some quantitative differences were established (Table 4). As main compound, allyl ITC showed an average relative abundance of 77%, which raised above 88% in populations DER089 and DER103. From them, DER089 showed the highest absolute value (GC-peak area units). There was a 6-fold difference between this population and the population with the lowest total value (DER045, \(183\times 10^{6}\)), which also showed exceptionally low levels in relative abundance (45%). In addition, 3-butenyl ITC (I2) and 3-methylbutyl ITC (I3) added an average relative abundance of 2.0% (Table 4). In both cases, DER045 showed the lowest absolute level and DER087, the highest one. The differences in GC-peak area units among them were 7-fold and 11-fold for compounds I2 and I3, respectively. Moreover, benzyl ITC (I6) and phenylethyl ITC (I7) were detected in all materials except for DER045, and hexyl ITC (I5) was only detected in this material as traces. Finally, pentyl ITC (I4) was only identified as traces (18 populations) or not detected (Table 4).