## 3 Results  
Minimal Inhibitory Concentration (MIC) of the Single Natural Compounds and of the Most Advantageous Synergistic Mixtures  
Table 1 shows the MICs of EOs and bacLP17 used alone against the indicator strain _L. monocytogenes_ NCTC 10888. Among the plant-derived compounds, _T. vulgaris_ was the most effective, and good anti-_Listeria_ activity also emerged from the bacteriocin, bacLP17. Tables 2-4 show the antibacterial activity against _L. monocytogenes_ NCTC 10888 of the most advantageous synergistic mixtures (expressed as MIC values), chosen based on the FIC-Index. In all tests, carried out using EO/EO associations and EO/bacLP17 combinations, a synergistic effect emerged. EO/EO and EO/bacLP17 were effective at very low concentrations that decreased up to 20 and 40 times for EO/EO and EO/bacLP17, respectively, compared to the MIC of the single compounds. Edible Antimicrobial Coating Added with EOs by Theselves or in Association against L. monocytogenes NCTC10888 on Artificially Contaminated Shrimp Samples  
The anti-_Listeria_ properties of all the chosen EOs were confirmed even when singularly added to the coatings. In this study, the synergistic effects of EOs mixtures on _L. monocytogenes_ were also investigated. When the EOs were used in association, the FIC-Index showed good synergy between the natural compounds inside the coating, with an anti-_Listeria_ activity obtained at values much lower than when used alone (Tables 1-3). \begin{table}
\begin{tabular}{c c c c c c} \hline _C. lemon_ & _C. lemon_ & _C. lemon_ & _M.piperta_ & _M.piperta_ & _S. officinalisis_ \\ _M.piperta_ & _S. officinalisis_ & _T. vulgaris_ & _S. officinalisis_ & _T. vulgaris_ & _T. vulgaris_ \\
**bacLP17** & **bacLP17** & **bacLP17** & **bacLP17** & **bacLP17** & **bacLP17** \\ \hline
3 \(\mu\)L/mL & 3 \(\mu\)L/mL & 3 \(\mu\)L/mL & 3 \(\mu\)L/mL & 3 \(\mu\)L/mL & 6 \(\mu\)L/mL \\ +1.5 \(\mu\)L/mL & +3 \(\mu\)L/mL & +0.8 \(\mu\)L/mL & +3 \(\mu\)L/mL & +1.5 \(\mu\)L/mL & +0.4 \(\mu\)L/mL \\ +0.8 \(\mu\)L/mL & +1.5 \(\mu\)L/mL & +0.8 \(\mu\)L/mL & +0.8 \(\mu\)L/mL & +0.4 \(\mu\)L/mL & +1.5 \(\mu\)L/mL \\ \hline \end{tabular}
\end{table} 
Table 4: MICs of the most advantageous EO/EO/bacLP17 combinations (chosen based on the FIC-Index) added to the coatings. Figures 1 and 2 report the mean values of the _L. monocytogenes_ NCTC 10888 viable counts (log CFU/g) detected in the contaminated samples packaged either with doped (EOs by themselves or in association) or undoped (control) coatings, after storage at 4 \({}^{\circ}\)C.  
Figure 1: Coating added with EOs by themselves and at the respective MIC values, applied on artificially contaminated shrimp samples: _Cirrus lemon_ (**a**), _Menta piperita_ (**b**), _Salvia officinalis_ (**c**), _Thymus vulgaris_ (**d**). Experiments were performed in triplicate. _p_-values of <0.05 (*), \(p\) < 0.01 (**) and \(p\) < 0.001 (**) were considered significant by _t_-test and ANOVA. Figure 2: Coating added with different EOs association, applied on artificially contaminated shrimp samples: _C. limon_/_M. piperita_ (**a**), _C. limon_/_S. officinalis_ (**b**), _C. limon_/_T. vulgaris_ (**c**), _M. piperita_/_S. officials_ (**d**), _M. piperita_/_T. vulgaris_ (**e**) and _S. officials_/_T. vulgaris_ (**f**). Experiments were performed in triplicate. _p_-values of < 0.05 (*), \(p\) < 0.01 (**) and \(p\) < 0.001 (**) were considered significant by _t_-test and ANOVA. The results showed good anti-_Listeria_ activity for the coating with EOs added by themselves, compared to the control, but with significant differences in the action times (Figure 1). _M. piperita_ was effective in controlling the growth of _L. monocytogenes_ NCTC10888 as early as 24 h after the study, showing a 3 log difference compared to the control (_p_ < 0.001) (Figure 1b). The same result was obtained using _C. limon_ (_p_ < 0.001), but from the third day (Figure 1a). In both cases the activity was maintained until the end of the experiments. _S. officinalis_ and _T.