## 3 Results and Discussion
### Effect of the Incorporation of the Valorized Pomace Ingredient in Dry-Cured Sausages
Nitrites control the proliferation of bacteria that causes meat spoilage [48], and they also contribute to the control of other pathogenic microorganisms, such as _E. coli_ O157:H7,  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Negative Control**} & \multicolumn{2}{c}{**Positive Control**} & \multicolumn{2}{c}{**Low Level**} & \multicolumn{2}{c}{**High Level**} & \multicolumn{2}{c}{_\(p\)**-Value**} \\ \hline Moisture & 28.1 & \(\pm\) & 1.5 & 28.3 & \(\pm\) & 1.1 & 26.9 & \(\pm\) & 1.1 & 27.7 & \(\pm\) & 1.0 & 0.302 \\ Aw & 0.829 & \(\pm\) & 0.011 & 0.833 & \(\pm\) & 0.013 & 0.824 & \(\pm\) & 0  
S. aureus, and Salmonella [49]. The protective effect against pathogens by the addition of ascorbic acid and nitrites was not perceived in PC sausages. It should be considered that other types of studies, such as challenge tests, would be required to further investigate this effect. At the industrial level, ascorbic acid is generally added together with nitrifying salts to increase the stability of nitrites. Additionally, this acid influences reducing pH, as well as exhibiting antioxidant and antimicrobial activities [10]. Significant changes in color were detected among dry-cured sausages, and only the lightness was similar in all groups (Table 5). The PC group presented significantly higher a* and lower b* than the NC group. In general, the addition of the RGP ingredient to dry-cured sausages had no significant effect on color variation compared to the NC. However, a significantly lower chroma was found in the HL compared to the NC group. In addition, the redness values of dry-cured sausage with RGP (LL, HL) and NC were also similar, since the levels of pomace added were low enough to avoid color modifications in the meat product. In this line, previous studies have also reported that the L* values of dry-cured sausage were not affected by the incorporation of grape-seed extracts [17; 32; 33]. The redness value was like that reported by [PERSON] (2016) [34] in Turkish dry-cured sausage with grape-seed flour. This similarity might be justified by the color pigments present in grapes. The effect of the nitrite-enhancing a* value in PC was somewhat expected, considering the role that nitrites play in the formation of the red curing pigment nitrosomyoglobin [13]. Moreover, the PC batch exhibited a significant difference compared to the NC in terms of the b* value, which was the highest. These variations in instrumental color coordinates also resulted in changes in hue and chrome values. In line with our results, [PERSON] et al. (2020) [11] reported increasing values of CIE a* and reduced values of CIE b* in dry-cured loin due to the addition of nitrifying salts. Therefore, nitrifying salts are not only responsible for the higher redness but also for the lower yellowness of the dry-cured meat products. The mean values of TBA-RS were low (<0.5 mg MDA kg\({}^{-1}\)) for all groups, indicating low lipid oxidation during the drying process (Table 5). The PC batch showed a significantly lower TBA value compared to the NC batch. Both levels of the RGP ingredient (LL and HL batches) presented intermediate values, which could indicate a slight tendency to decrease lipid oxidation. The mechanism by which nitrite inhibits lipid oxidation is clearly defined, including the formation of nitrosyl-myoglobin (MbNO) and nitric oxide ferrous complexes, the synthesis of S-nitrosocysteine, and the inhibition of the Fenton reaction due to the neutralization of the release of Fe\({}^{2+}\) from myoglobin [13]. Previous studies have reported an intense antioxidant effect from the addition of grape-seed extracts [9; 17] and grape-seed flour [34]. A possible explanation for these differences regarding the antioxidant effect of RGP could be that the mentioned studies have added extracts from the grape seed, in which