## 3 Results and Discussion
### Instrumental Color  
The instrumental color was significantly different between the groups, specifically in \(a^{\star}\), \(b^{\star}\), and \(h^{\circ}\). The NITRASC group reached the highest values in \(a^{\star}\) and the lowest in \(b^{\star}\) and \(h^{\circ}\). The lowest values in \(a^{\star}\) in the nitrite-free sausages reveal that the pomace addition cannot compensate for the absence of nitrites. In addition, the pomace-added groups were not different from the Control group in any instrumental color coordinate (Table 4), which suggests that the pomace does not have any beneficial effect (either at 0.5 or at 3%) to improve dry-cured sausage color. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Control** & **NITRASC** & **0.5\%Pomace** & **3\%Pomace** & \(p\) \\ \hline Lipid oxidation (mg MDA kg\({}^{-1}\)) & 1.9 \(\pm\) 0.4 a & 0.6 \(\pm\) 0.0 b & 0.6 \(\pm\) 0.1 b & 0.5 \(\pm\) 0.1 b & \textless{}0.001 \\ Protein oxidation (nmols carbonyls mg protein\({}^{-1}\)) & 3.0 \(\pm\) 0.6 & 2.5 \(\pm\) 0.3 & 2.8 \(\pm\) 0.2 & 2.8 \(\pm\) 0.4 & 0.345 \\ \hline \hline \end{tabular} The results are expressed as mean \(\pm\) standard deviation and significance (\(p\)) from a one-way ANOVA. Different letters in the same row indicate significant differences in [PERSON]’s test.  
\end{table} 
Table 3: Lipid and protein oxidation of Control dry-cured sausages and dry-cured sausages with synthetic additives (NITRASC) or with stabilized grape pomace at 0.5% (0.5%Pomace) or 3% (3%Pomace). The lack of effect of the pomace is partially in line with those reported for pork burgers with the same pomace after 7-day storage, with no effect on \(L^{*}\) and \(a^{*}\) but higher values in \(b^{*}\) in the samples with pomace at 3% than in the Control ones (on day 1, the effect was only significant on \(h^{\circ}\)) [20]. The results are roughly in line with previous studies comparing \(L^{*}\), \(a^{*}\), and \(b^{*}\)[18] and \(C^{*}\) and \(h^{\circ}\)[17] of dry-cured sausages with sodium nitrite vs. with a grape-seed-based extract. The lack of differences in \(L^{*}\) between the pomace and NITRASC groups (Table 4) is in line with those previous results [18]. However, in contrast to our results, similar values for \(a^{*}\)-, \(b^{*}\)-[18], and \(a^{*}\)-based color parameters \(C^{*}\) and \(h^{\circ}\)[18] between sausages manufactured with a grape-seed-based extract and with nitrites were found. Those similarities implied that the extract and nitrites influenced color development to a similar extent, even though grape by-products are not rich in nitrites. It was suggested that color might have developed in the extract-containing sausages through an alternative pathway involving zinc (yielding the stable red compound Zn-protoporphyrin) instead of nitrites (which result in nitrosomyoglobin) [18], which has already been described in Parma ham [53; 54]. However, our results indicate that those reactions were not noticeable when white grape pomace was used. The lack of agreement between the results in Table 4 and those studies might be due to the differences between the nitrite-containing sausages (theirs included only sodium nitrite, whereas ours also included L-ascorbic acid) and the compounds and grape products included in the related sausages (they added a grape seed extract, hydroxytyrosol, andtocopherol [17; 18]), whereas we added a stabilized grape pomace from pressed grapes after wine production including seeds, skin, and pulp). In addition to differences in the content in grape compounds promoting Zn-protoporphyrin formation, further differences might be involved. In this regard, differences in the microorganisms might have been relevant.