## 3 Results and Discussion
### Determination of the Oxidative Stability  
Table 4 shows the oxidative stability of the grapeseed oil fortified with the WP and RP extracts with the optimal TPC and FRAP values at different concentrations (10%, 20% and 30% \(w/w\)). Unaltered rapeseed oil samples and samples fortified with a conventional synthetic antioxidant (BHT at 200 ppm) were evaluated as the controls. Previous studies have indicated that it is possible to increase the induction time (IT) of edible oils by adding antioxidant extracts derived from various plant by-products to them and obtain high value-added products with an improved oxidative stability and shelf life [61; 62; 63; 64; 65; 66]. As shown in Table 4, the grapeseed oil without any fortification (the control) had the lowest oxidation stability, with an IT of 4.65 \(\pm\) 0.16 h. The grapeseed oils fortified with BHT and with red SGP at 10% increased in their stability by 13% (\(p<0.05\)). In addition, using the red SGP provided a higher oxidative stability than using the white SGP at all the concentrations tested. However, using either RP or WP, the AAI achieved was much higher (\(p<0.05\)) than that of the control, and when using BHT, in particular when fortifying the oil with 30% of the extracts, increases over the control of 25% and 39% were obtained for WP and RP, respectively. Sonication treatment was applied to mix the different extracts with the grapeseed oil, improving the transfer of antioxidant components from the extract to the oil and obtaining a more homogeneous distribution of antioxidant compounds [41; 67]. As reported by [PERSON] et al. (2024), the use of sonication to increase the solubility and miscibility of extracts in oils can increase the presence of structured phenolic lipids, which work as natural antioxidants [68]. These data suggest that the optimal sample should have a prolonged IT, with this effect being more evident when increasing the concentration of the extract. However, the extracted antioxidant compounds, as well as delaying the oxidation of the oil, may exert additional bioactivity [69]. Furthermore, interactions between these antioxidant compounds and other molecules present in the matrix may have a positive or negative impact on the oxidative stability of food systems, resulting in synergism or antagonism [70]. Future studies should provide a detailed metabolomic profile of the extracts obtained for a fuller understanding of their bioactivity. In addition, monitoring the fatty acid profile of fortified grapeseed oil during storage is crucial to assessing how these extracts affect its stability over time. The industrial scalability and cost-effectiveness of using these natural extracts and their potential interactions with other components of food will need to be assessed. Finally, sensory evaluations and studies on consumer acceptance are required. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**WP**} & \multicolumn{2}{c}{**RP**} \\ \cline{2-5}  & **IT (h)** & **AAI** & **IT (h)** & **AAI** \\ \hline Grapeseed oil & 4.65 \(\pm\) 0.16 \({}^{\text{Bc}}\) & 1.00 & 4.65 \(\pm\) 0.16 \({}^{\text{Ac}}\) & 1.00 \\ Grapeseed oil + BHT at 200 ppm & 5.24 \(\pm\) 0.14 \({}^{\text{Bb}}\) & 1.13 & 5.24 \(\pm\) 0.14 \({}^{\text{Ab}}\) & 1.13 \\ Grapeseed oil + 10\% SGP extract & 4.82 \(\pm\) 0.14 \({}^{\text{Bc}}\) & 1.03 & 5.26 \(\pm\) 0.53 \({}^{\text{Ab}}\) & 1.13 \\ Grapeseed oil + 20\% SGP extract & 5.32 \(\pm\) 0.02 \({}^{\text{Bb}}\) & 1.14 & 5.69 \(\pm\) 0.57 \({}^{\text{Ab}}\) & 1.22 \\ Grapeseed oil + 30\% SGP extract & 5.79 \(\pm\) 0.23 \({}^{\text{Ba}}\) & 1.25 & 6.46 \(\pm\) 0.88 \({}^{\text{Aa}}\) & 1.39 \\ \hline \hline \end{tabular} Data are expressed as the mean \(\pm\) standard deviation (\(n=3\)). Different letters indicate statistically significant differences (\(p<0.05\)) between the type of SGP (capital letters) and the type of sample fortified (lowercase letters), according to ANOVA (two-way) and [PERSON]’s test.  
\end{table}