## 3 Results and Discussion
### Volatile Compounds
The pomace at 0.5% did not cause differences from the Control group in any compounds, whereas at 3%, differences appeared in 2,3-butanediol and hexanal. The differences between the pomace groups and the NITRASC one were larger: four compounds differed when it was added at 0.5% (3-hydroxybutan-2-one, hexanal, 2-phenylacetaldehyde, and \(\alpha\)-caryophyllene), and three when it was added at 3% (2,3-butanediol, hexanal, and 2-phenylacetaldehyde). Only three of the seven compounds different between the groups were identified in the pomace, whereas the others were not. Regarding those three compounds, all of them were aldehydes that can be generated through lipid oxidation reactions, and they followed a different trend: hexanal and 2-phenylacetaldehyde reached the lowest content in the NITRASC group, whereas nonanal reached the highest. Hexanal, an estimator for lipid oxidation, had the highest estimated content in the 3%Pomace group, with a sharp increase (almost tripled) with respect to the Control one, whereas the lowest content appeared in the NITRASC group. Two phenomena might be mainly involved in these differences: lipid oxidation reactions in the sausages, and the hexanal content in the added pomace. Regarding lipid oxidation, the results for hexanal were not correlated with the results from the TBARS test (\(p\) = 0.248). This might be due to the fact that the TBARS test did not measure hexanal but malondialdehydeheyde instead, which is generated at a different stage of the lipid oxidation reactions. Regarding the hexanal content of the pomace (281 ug/kg\({}^{-1}\) pomace), it was not sufficient to triple the sausage content (650.0 vs. 225.5 ug kg\({}^{-1}\) sausage in the 3%Pomace and Control groups, respectively) or double the values when added at 3% instead of at 0.5% (650.0 vs. 298.8 ug kg\({}^{-1}\) sausage, respectively). However, a relevant contribution of the pomace should not be ruled out since it contains not only hexanal but also its precursors. Hexanal has been identified as an odorant of dry-cured meat products [18; 55], and, therefore, changes in it are expected to be critical for the sausage odor and flavor. However, it was not correlated with the off-odor and off-flavor (\(p\) = 0.699 and 0.233), although it was with juiciness and defective texture (R: \(-\)0.663 and 0.919, \(p\) = 0.001 and <0.001, respectively). 2-Phenylacetaldehyde, generated from amino acid degradation reactions as well as lipid oxidation, followed a similar trend to hexanal, except for the lack of differences between the two pomace groups. This suggests, again, that the pomace might not have been the main source of this compound, and that its production might have occurred in the sausages during ripening. This compound has been identified as a dry-cured meat product \begin{table}
\begin{tabular}{c c c c} _Alcohols_ & & _Esters_ & \\ \hline Ethanol & 71.3 \(\pm\) 61.9 & Ethyl hexanoate & 12.1 \(\pm\) 2.1 \\
3-Methylbutan-1-ol & 5.0 \(\pm\) 8.6 & Ethyl octanoate & 15.2 \(\pm\) 3.0 \\ (Z)-3-Hexen-1-ol & 113.2 \(\pm\) 21.8 & Ethyl decanoate & 2.3 \(\pm\) 4.0 \\ (E)-2-Hexen-1-ol & 734.9 \(\pm\) 96.9 & Hexanediolic acid, dibutyl ester & 8.8 \(\pm\) 8.4 \\ \cline{2-3} Hexan-1-ol & 862.2 \(\pm\) 114.5 & _Terpenes_ & \\ \cline{2-3}
2-Ethyl-2-hexen-1-ol & 46.8 \(\pm\) 7.1 & Alcanfor & 13.9 \(\pm\) 24.0 \\ \cline{2-3} Phenylmethanol & 4.5 \(\pm\) 4.2 & _Others_ & \\ \cline{2-3}
2-Phenylethanol & 20.2 \(\pm\) 0.9 & Acetic acid & 45.2 \(\pm\) 44.5 \\ \cline{2-3} _Aldehydes_ & & Oxime-methoxy-phenyl & 448.4 \(\pm\) 122.8 \\ \cline{2-3} Hexanal & 281.3 \(\pm\) 55.6 & 2,2,4,6,6-Penta-methyl-heptane & 28.7 \(\pm\) 3.3 \\ \cline{2-3}
2-Phenylacetaldehyde & 156.6 \(\pm\) 23.7 & & \\ \cline{2-3} Benzaldehyde & 76.0 \(\pm\) 10.7 & & \\ \cline{2-3} Nonanal & 48.7 \(\pm\) 6.4 & & \\ (E)-Hex-2-enal & 97.0 \(\pm\) 11.9 & & \\ \hline \end{tabular} The results are expressed as mean \(\pm\) standard deviation from three replicates.  
\end{table} 
Table 6: Volatile compounds (ug kg\({}^{-1}\)) isolated in the stabilized white wine pomace.