## 3 Results and Discussion
### Oxidation Status  
Lipid oxidation (measured as MDA content) was significantly higher in the Control group than in the others, with values 3.2-3.8 times higher (Table 3). The values for the groups with pomace (0.5%Pomace and 3%Pomace) and sodium nitrite and ascorbic acid (NITRASC) were similar, which reveal that the pomace was as effective as the synthetic additives at hindering lipid oxidation. It should be noted that there were not significant differences between the 0.5 and 3% pomace groups (Table 3) and, therefore, the lower pomace content was sufficient to reach the maximum effect. This indicates that the antioxidant activity of the grape pomace (68.7 \(\pm\) 7.4 mmol Trolox g\({}^{-1}\)) was effective at preventing oxidation when added at a low dosage to a food matrix where interactions of phenols with proteins might happen, as well as changes during the ripening stage.  
The decrease in lipid oxidation caused by the pomace is in line with a previous study applying the same pomace to burgers, which reported less lipid oxidation in the samples with 0.5, 1, or 3% pomace than in the Control samples and even than in burgers with sulfites [20]. They also match previous results on a grape-seed-based extract (with added hydroxytyrosol and tocopherol), which resulted in similar values to sodium nitrite in the lipid oxidation of dry-cured sausages [18]. The decrease in lipid oxidation might be relevant to increase the shelf-life of the sausages. This is especially advisable when additional oxidative factors are involved, such as slicing, which is increasingly performed to meet new consumers' preferences for packaged sliced dry-cured products.  
The antioxidant activity of grape pomace has already been demonstrated [4; 5; 6]. This effect was proved as useful in food systems, including muscle foods such as burgers and salmon [13; 50]. Our study demonstrates that white grape pomace stabilized by blanching and HHP can be used to improve the lipid stability of dry-cured sausages, and it can be a green alternative to synthetic antioxidants.  
As for protein oxidation (measured as carbonyl content), no differences between the four sausage groups were found (Table 3), the pomace and the synthetic additives not being useful to prevent protein oxidation. Despite lipid and protein oxidation being generally intertwined, our results showed that there was not a strong correlationship (R: 0.394, \(p=0.086\)). Previous studies have also reported that both parameters are not always affected to the same extent by several factors in dry-cured products [48; 51], since they measure compounds generated at different stages of the oxidation reactions. The lack of effect of the pomace on protein oxidation (Table 3) matches the results from a previous study applying the same pomace to burgers, which reported no differences after 7-day storage, and an inconsistent effect before storage [20]. Previous studies including grape-based products in dry-cured meat products have not researched their effect on protein oxidation [17; 18; 19]. For other meat products, the results have been inconsistent: for example, grape by-product extracts lowered the free thiol content in beef patties [50] but had no effect on lamb patties [13] even though in both studies they delayed lipid oxidation. Further studies focused on protein oxidation are advisable to broaden the knowledge on the oxidation phenomena occurring in dry-cured products when phenols or grape pomace are added. To sum up, the results suggest that despite the prevention of lipid oxidation (Table 3) and the activity of some phenols to prevent protein oxidation [52], the pomace had no noticeable effect to hinder protein oxidation in dry-cured sausages.