## 3 Results and Discussion
### Effect of Breed and Finishing Diet on Volatile Compounds
#### 3.2.6 Esters, Ethers, Furans, Nitrogen Compounds and Sulfur Compounds
Concretely, 2-proprem-1-amine represented the majority substance within this family, and the BU group values almost duplicate those of JN fools (\(p<0.001\)). On the other hand, the type of diet also significantly (\(p<0.05\)) influenced the total nitrogen compounds contents, presenting higher values in the D1 group in comparison with the D2 one. In this case, among individual compounds, significant (\(p<0.05\)) differences were observed in the minority nitrogen substances (diazene, dimethyl- and propane, 2-nitro); whereas the predominant compounds showed similar (\(p>0.05\)) values in both diet groups. This family represented the second most plentiful of the total volatile compounds in all groups (Figure 1). However, this class of substances has not been previously detected in any volatile profile of raw foal meat [25; 26; 27]. Considering the four group of studies, BU-D1 presented the highest amounts, while JN-D2 had the lowest values. However, any significant interactions among the main factors (B \(\times\) D) were observed, expect for diezene, dimethyl- and 2-propanamine. Regarding the sulfur compounds, only one substance was detected, named carbone disulphide. Table 4 showed that breed significantly (\(p<0.05\)) affected carbon disulphide amounts, being higher in JN fools than BU ones (8.49 _vs._ 6.62 \(\times\) 10\({}^{4}\)/g fresh meat, respectively). According to the literature, this volatile compound could be a product of the enzymatic proteolysis of sulfur-containing amino acids [85], but can be also originated from fungicides used in agriculture [86]. However, there is scarce information about the amino acid profile of both breeds, so it is complicated to compare these results and understand the exact origin of this compound. However, carbon disulphide corresponded to a very low fraction of the total volatile compounds, being the family with the second (JN foals) and the lowest (BU foals) contribution to the volatile profile (Figure 1). Concerning the diet effect, statistical analysis showed a tendency (\(p<0.1\)) among both diets, recording higher values in the D2 group compared with D1 foals (\(8.48\) vs. \(6.88\times 10^{4}/\mathrm{g}\) fresh meat, respectively). This difference is consistent with data previously reported [54; 64; 65]; in fact, several authors observed that animals with grass-based diets obtained higher contents of sulfur compounds than those finished with concentrates. [PERSON] and [PERSON] [65] affirmed that this trend could be explained by the fact that herbage diets can produce an increase in free amino acids. Hence, the formation of sulfur compounds could be favored, since these substances derive from the enzymatic proteolysis of the sulfur-containing amino acids [85], as aforementioned. However, also in this case, the contribution of carbon disulphide on the total volatile contents was minimal, as shown in Figure 1. The four groups of the study showed similar values, except for JN-D2 foals, which presented the highest values of carbon disulphide. However, any significant interactions were observed among the main factors. As a general conclusion, it is well known that fat content plays an important role both in volatile compounds and in the aroma of meat and meat products [22]. Thus, the volatile compounds derived from lipids are the most important in meat [22; 29], and the special property of lipids to solubilize and serve as a reservoir for these volatile compounds also stands out. Therefore, it is expected that meat with a higher fat content has a higher content of volatile compounds, and more specifically of lipid-derived ones. In this study, BU foals (\(5.01\%\) BU _vs._\(3.79\%\) JN), as well as animals fed with diet 1 (\(4.88\%\) D1 _vs._\(3.76\%\) D2), had the highest fat content. Therefore, a large part of the results obtained in the present study can be attributed to both the amount and the lipid composition of the meat.