## 3 Results and Discussion
### Characterization of Basil Pesto Samples
#### 3.2.2 Antioxidant Parameters
However, after 90 days of storage, a significant increase in TPC was observed for all samples. Such an increase may be related to the effect of pH on the retention of polyphenols. Considering that the pH values of the samples ranged from 4.8 to 3.62, it is probable that the acid condition promotes the stabilization of polyphenols. Interestingly, [PERSON] and [PERSON] [39] demonstrated that samples of fortified food tended to have less TPC reduction under acidic conditions. This would also account for the trend observed in bioactive compounds quantified by UPLC. Coefficient of correlation (r), regression equations, and limits of detection (LOD) and quantification (LOQ) for each antioxidant compound are reported in Table 5.  
As reported in Table 6, enrichment enables attainment of samples fortified with a wide array of bioactive compounds not found in commercial pesto sauce. A total of 10.55 mg kg\({}^{-1}\) and 10.40 mg kg\({}^{-1}\) of hydrotyrosol and tyrosol, respectively, were detected in the F+ and P+ samples and a significant increase in compounds inherently occurred in the basil leaves (quercetin, caffeic acid, p-coumaric acid, rutin, and rosmarinic acid). As discussed for TPC, the trend evaluation of individual phenolic compounds also showed a significant increase in certain compounds (caffeic acid and p-coumaric acid) during storage. The results suggest that the stability of the phenolic compounds could be strongly linked to the concurrent effect of pH and the structure of the phenolic compounds. [PERSON] and [PERSON] [40] observed changes in the absorption spectra to the structures of the different compounds and found the stability of phenolic compounds under different pH conditions, depending on the presence of phenolic OH groups, conjugated to the benzene ring. Considering the phenolic profile induced by the pasteurization process, it can be determined that the thermal treatment does not significantly affect the amount of individual chemicals compared with fresh samples. Particularly, increases in tyrosol, oleuropein, and rosmarinic acid were detected after pasteurization. As reported in the literature [41], the thermal treatment could promote the cleavage of chemical bonds, allowing a more effective release of chemicals to the medium. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Compounds** & **Regression Equation** & **R\({}^{2}\)** & \
\begin{tabular}{c} LOD \\ \(\mu\)g g\({}^{-1}\) \\ \end{tabular} &
\begin{tabular}{c} LOQ \\ \(\mu\)g g\({}^{-1}\) \\ \end{tabular} \\ \hline Hydroxytyrosol & y = 25.77\(\mathrm{x}-24.41\) & 0.9999 & 0.0888 & 0.05 \\ Protocatechic acid & y = 119.35\(\mathrm{x}\) + 645.19 & 0.9998 & 0.0656 & 0.04 \\ Tynosol & y = 41.25\(\mathrm{x}-49.09\) & 0.9998 & 0.0456 & 0.02 \\ Chlorogenic acid & y = 52.15\(\mathrm{x}-100.73\) & 0.9999 & 0.0532 & 0.03 \\ Caffeic acid & y = 112.33\(\mathrm{x}-110.33\) & 0.9997 & 0.0782 & 0.05 \\ p-coumaric acid & y = 119.96\(\mathrm{x}\) + 50.26 & 0.9999 & 0.0988 & 0.20 \\ Quercetin & y = 59.097\(\mathrm{x}+119.01\) & 0.9999 & 0.0456 & 0.02 \\ Oleuropein & y = 46.63\(\mathrm{x}+51.21\) & 0.9997 & 0.0123 & 0.04 \\ Luteolin & y = 74.58\(\mathrm{x}-136.08\) & 0.9996 & 0.0234 & 0.05 \\ Apigenin & y = 100.91\(\mathrm{x}-296.57\) & 0.9989 & 0.0345 & 0.02 \\ Rutin & y = 46.07\(\mathrm{x}-14.44\) & 0.9999 & 0.04536 & 0.04 \\ Rosmarinic acid & y = 228.72\(\mathrm{x}-194.39\) & 0.9997 & 0.1123 & 0.45 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Method development through UPLC-PDA. In the present study, the antioxidant activity was evaluated by two different assays (DPPH and ABTS) for both control and fortified pesto sauces (Table 4). The AE extract seemed to be more effective in enhancing the antioxidant activity against the ABTS radical cation of the fresh enriched sample with an increase of about 32.22%. In contrast, an increase of 6.82% was detected for the enriched pasteurized sample. However, the stability of antioxidant assays showed the same performance for all samples during storage.