## 3 Results and Discussion
### Antimicrobial Activity
(2023) [41], a strong antibacterial activity with a maximum zone of inhibition of 15.50 mm was determined for an oil extract of milk thistle leaf against _Staphylococcus aureus_. Moreover, antifungal activity was also reported, with a maximum zone of inhibition (13.83 mm) in tests against _Aspergillus versicolor_. [PERSON] [44] determined a stronger activity of milk thistle oil compared to our results. This was especially noticeable for _Escherichia coli_--6 mm, _Staphylococcus aureus_--7 mm, and _Candidia albicans_--9 mm. Grape seed oil (Table 3) showed the strongest activity against _Staphylococcus aureus_ CCM 2461 (5.32 mm) and _Streptococcus pneumoniae_ CCM 4501 (0.11 mm). [PERSON] et al. [45] determined antibacterial properties of different active emulsified films containing grape seed oil (0.15 g/g). These active films showed antibacterial effects against _Salmonella typhimurium_ (12.10 mm), _Staphylococcus aureus_ (10 mm), _Pseudomonas fluorescens_ (11.06 mm), and _Escherichia coli_ 157:H7 (11.03 mm). Walnut oil showed the highest activity against _Yersinia enterocolitica_ CCM 5671 (6.33 mm) (Table 3). The extracts from walnut kernels were reported to inhibit strains of _Escherichia coli_, _Bacillus subtilis_, and _Klebsiella pneumoniae_ in a study by [PERSON] et al. [46]. Generally, it can be stated that the antimicrobial activity of all the tested oils can be effectively utilised in salad dressings because this kind of oil is suitable for cold culinary applications, especially for salads. The addition of selected oils can not only improve the nutritional value but also introduce an antimicrobial effect, facilitating a prolonged shelf life when packing a seasoned, ready-to-eat salad. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Microorganism** & **FO [mm]** & **PO [mm]** & **MTO [mm]** & **GO [mm]** & **WO [mm]** \\ \hline \multicolumn{6}{c}{**Yeast**} \\ \hline _Candidia albicans_ CCM 8186 & 0.31 \(\pm\) 0.01 a & 0.09 \(\pm\) 0.01 c & 0.08 \(\pm\) 0.01 c & 0.12 \(\pm\) 0.01 b & 0.12 \(\pm\) 0.01 b \\ \hline \multicolumn{6}{c}{**Gram-negative bacteria**} \\ \hline _Haenophilus influenzae_ CCM 4454 & 0.09 \(\pm\) 0.01 e & 0.22 \(\pm\) 0.01 a & 0.03 \(\pm\) 0.01 e & - & 0.09 \(\pm\) 0.01 b \\ _Escherichia coli_ CCM 3954 & 0.09 \(\pm\) 0.01 d & 0.31 \(\pm\) 0.01 a & 0.03 \(\pm\) 0.01 e & 0.13 \(\pm\) 0.01 c & 0.17 \(\pm\) 0.01 b \\ _Klebsiella pneumoniae_ CCM 2318 & 1.31 \(\pm\) 0.02 d & 3.68 \(\pm\) 0.14 a & 3.11 \(\pm\) 0.11 b & 2.24 \(\pm\) 0.12 c & 2.11 \(\pm\) 0.09 c \\ _Yersinia enterocolitica_ CCM 5671 & 2.09 \(\pm\) 0.05 d & 2.11 \(\pm\) 0.01 d & 3.13 \(\pm\) 0.02 b & 2.64 \(\pm\) 0.03 c & 6.33 \(\pm\) 0.02 a \\ _Salmonella enterica_ subs. _entrica_ CCM 3807 & 3.07 \(\pm\) 0.04 e & 3.63 \(\pm\) 0.03 d & 4.31 \(\pm\) 0.03 b & 4.11 \(\pm\) 0.02 c & 4.65 \(\pm\) 0.03 a \\ \hline \multicolumn{6}{c}{**Gram-positive bacteria**} \\ \hline _Staphylococcus aureus_ CCM 2461 & 2.61 \(\pm\) 0.07 c & 2.32 \(\pm\) 0.01 d & 4.14 \(\pm\) 0.03 b & 5.32 \(\pm\) 0.03 a & 2.34 \(\pm\) 0.02 d \\ _Clostridium perfringens_ CCM 4991 & 2.11 \(\pm\) 0.01 e & 2.02 \(\pm\) 0.01 d & 6.31 \(\pm\) 0.02 a & 3.08 \(\pm\) 0.01 c & 6.11 \(\pm\) 0.02 b \\ _Bacillus cereus_ CCM 2010 & 4.58 \(\pm\) 0.08 a & 4.32 \(\pm\) 0.03 b & 4.05 \(\pm\) 0.06 c & 4.31 \(\pm\) 0.02 b & 2.65 \(\pm\) 0.03 d \\ _Streptococcus pneumoniae_ CCM 4501 & - & 0.14 \(\pm\) 0.01 a & - & 0.11 \(\pm\) 0.02 a & - \\ \hline \multicolumn{6}{c}{**Fom–fixed seed oil; PO—poppy seed oil; MO—milk thistle seed oil; GO—grape seed oil; WO—walnut oil; mean \(\pm\) standard deviation; different letters in a column denote mean values that statistically differ one from another; mm—millimetre.**} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Antimicrobial activity of analysed oils.