## 3 Results and Discussion
aureus_ was the most sensitive bacteria, showing strong inhibition and bactericidal effects across all conditions. In contrast, _E. coli_ displayed resistance to the crude extract (IC50 and MBC > 10%), but its susceptibility increased following intestinal digestion (IC50 \(\leq\) 0.625%). Similarly, the inhibitory effect against _S. enterica_ improved post-intestinal digestion, although the bactericidal activity remained invariable (MBC \(\geq\) 10%). _L. monocytogenes_ showed moderate sensitivity, with some fluctuations throughout the digestive phases. In general, the inhibitory activity of the extract increased post digestion (Table 2), especially against Gram-negative strains, where the IC50 values decreased to a third. However, no differences were observed in the MBC values. Nevertheless, in the case of Gram-positive foodborne bacteria, the inhibitory activity after gastric exposure to _L. monocytogenes_ decreased notably (Figure 2g). And the same phenomenon was observed for _S. aureus_ (Figure 2h). These findings suggest that digestion can alter the bioactivity of the compounds present in the extract, enhancing or reducing their antimicrobial potential depending on the bacterial target. Interestingly, a quantitative reduction in polyphenols did not correlate directly with a decrease in the antimicrobial activity, especially against Gram-negative bacteria. Figure 3 shows Pearson's correlation matrix of polyphenols' variation and the antimicrobial IC50 values in crude and digested extracts. A negative correlation, e.g., higher polyphenol concentration-lower IC50 values, is represented in lighter colours, meanwhile a positive correlation is represented in dark greyish green. As has been observed, the extract's antimicrobial activity against _S. aureus_ is potentially linked to quercetin-3-glucoside (Figure 3a). However, the IC50 value was maintained \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Strains** & & **Ce** & **GDe** & **IDe** \\ \hline _E. coli_ & IC50 & \textgreater{}10\% & 4.58\% & \(\leq\)0.625\% \\  & MBC & \textgreater{}10\% & \textgreater{}10\% & \(\geq\)10\% \\ \hline _S. aureus_ & IC50 & \textless{}0.625\% & 1.22\% & 0.72\% \\  & MBC & \textless{}0.625\% & \textless{}2.5\% & \textless{}2.5\% \\ \hline _S. enterica_ & IC50 & 4.98\% & 4.84\% & 1.67\% \\  & MBC & \textgreater{}10\% & \textgreater{}10\% & \(\geq\)10\% \\ \hline _L. monocytogenes_ & IC50 & 3.81\% & 7.19\% & 2.04\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Antimicrobial activity observed after foodborne pathogens’ exposure to the Albarino grape caract before and after gastrointestinal digestions. The first column collects the date for the crude extract (Ce), and subsequent columns refer to the assays performed after the extract’s exposure to each digestive process. GDe: gastric digestion of the extract; IDe: intestinal digestion of the extract. IC50 refers to the minimum concentration needed to eradicate 50% of the pathogen population. MBC refers to the minimal bactericidal concentration. Data are expressed in % of extract volume. Assays were performed in triplicate. after digestion despite quercetin-3-glucose reduction. This suggests a synergistic effect among polyphenols, where the combined presence of multiple compounds maintains the antimicrobial activity even when individual concentrations decline (Figure 3c). Such synergistic interactions have been reported for grape-derived polyphenols, enhancing antimicrobial efficacy through cooperative effects that may influence bacterial growth and metabolism [11; 31]. _E. coli_'s sensitivity to the extract increased after digestion. This may be linked on the one hand to the presence of gallic acid, procyanidins, epicatechingallate, and quercetin-3-glucuron in IDe, but on the other hand to a higher sensitivity to the gastrointestinal conditions with respect to the rest of the tested strains, which is reflected in Figure 2e. These same polyphenols have been linked to _L.