## 3 Results and Discussion
### Effect of the Incorporation of the Valorized Pomace Ingredient in Dry-Cured Sausages
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline  & **Negative Control** & \multicolumn{3}{c}{**Positive Control**} & \multicolumn{3}{c}{**Low Level**} & \multicolumn{3}{c}{**High Level**} & \multicolumn{3}{c}{**\(p\)-Value**} \\ \hline  & & & \multicolumn{8}{c}{Instrumental color} \\ L* & 45.0 & \(\pm\) & 2.6 & 44.5 & \(\pm\) & 1.7 & 44.4 & \(\pm\) & 1.1 & 42.4 & \(\pm\) & 2.1 & 0.197 \\ a* & 5.0 b & \(\pm\) & 1.1 & 7.7 a & \(\pm\) & 1.5 & 4.4 b & \(\pm\) & 0.6 & 4.0 b & \(\pm\) & 0.6 & 0.000 \\ b* & 12.1 a & \(\pm\) & 1.7 & 9.0 b & \(\pm\) & 1.7 & 10.3 ab & \(\pm\) & 1.0 & 9.8 ab & \(\pm\) & 1.1 & 0.019 \\ Chroma & 13.2 a & \(\pm\) & 1.4 & 12.0 ab & \(\pm\) & 1.0 & 11.2 ab & \(\pm\) & 1.1 & 10.6 b & \(\pm\) & 1.2 & 0.017 \\ Hue & 67.0 a & \(\pm\) & 6.2 & 49.0 b & \(\pm\) & 9.8 & 67.0 a & \(\pm\) & 2.3 & 68.0 a & \(\pm\) & 1.7 & 0.000 \\  & & & & & & & & & & & & & & \\  & & & & & & & & & & & & & & \\ TBA-RS & 0.5 a & \(\pm\) & 0.2 & 0.2 b & \(\pm\) & 0.0 & 0.3 ab & \(\pm\) & 0.0 & 0.4 ab & \(\pm\) & 0.1 & 0.013 \\ Carbonyls & 3.1 a & \(\pm\) & 1.0 & 2.3 ab & \(\pm\) & 0.4 & 1.8 b & \(\pm\) & 0.3 & 2.1 b & \(\pm\) & 0.3 & 0.016 \\ \hline  & & & & & & & & & & & & & & \\ \end{tabular}
\begin{tabular}{c c c c c c c c c c} \hline  & **Negative control** & **(NC: sausages manufactured without nitrites/RGP); positive control (PC: sausages manufactured with nitrites); low level (LL: sausages manufactured with 0.5% (\(w/w\)) RGP); high level (sausages manufactured with 1% (\(w/w\)) RGP). Oxidative parameters: lipid oxidation or TBA-RS (mg MDA kg\({}^{-1}\)), protein oxidation (mmols carbonyls mg protein\({}^{-1}\)). Different letters in the same row indicate significant differences in the Tukey test (\(p<0.05\)).  
\end{table} 
Table 5: Instrumental color parameters and oxidative parameters (TBA-RS and carbonyls) of dry-cured sausages “salchichön”. the concentration of polyphenols would be higher than in our valorized by-products (skin, seeds, and stalks). However, in a previous study, the addition of white grape pomace to burgers at different levels of inclusion (0.5, 1, or 3%) significantly decreased lipid oxidation compared to a negative control group without pomace, even compared to a positive control group including sulfites [31]. The addition of the RGP ingredient had a significant impact on protein oxidation, as measured by the carbonyl content (Table 5). Samples from the LL batch (0.5%) and HL batch (1%) presented significantly lower carbonyl contents than the samples from the NC group. However, the addition of nitrites (PC) did not lead to a decrease in protein oxidation in the dry-cured sausages. The effect of nitrite on protein oxidation is unclear, and there are contradictory results regarding its impact on protein carbonylation [5]. Depending on the concentration, sodium nitrite has both anti- and pro-oxidant outcomes on protein oxidation in meat products [50]. Regarding the observed effect of the RGP ingredient in our samples, this is consistent with the study by [PERSON] et al. (2013) [51] who incorporated grape-seed phenolic compounds into Chinese-style sausage. In this study, the inhibition of protein oxidation was attributed to the prevention of metmyoglobin formation by the competitive chelation of iron from myoglobin. However, there are also studies that do not describe this effect and even report an increase in carbonyl groups compared to sausages including nitrites or phenolic compounds [9; 12; 17; 32; 34], despite the influence of phenolic compounds on protein oxidation due to the chemical structure of the phenolic compounds and their interactions with the myofibrillar proteins [5]. In our study, the effect of the addition of the RGP ingredient on decreasing protein oxidation was somewhat unexpected, since it presented more effectivity than nitrifying salts. A previous study on model systems reported that protein oxidation is a complex group of reactions, and nitrite can act as both an antioxidant and a pro-oxidant on proteins [8].