# Innovative Sensor Approach to Follow _Campylobacter jejuni_ Development
## 3 Results and Discussion  
### GC-MS Results  
Chromotograms of analyzed samples were compared to highlight differences between control samples and _C. jejuni_ ones to see the variation of emitted VOCs in the headspace between T0 and T20. The comparison between control and _C. jejuni_ specimens at time T0 underlines no significant differences in terms of number and amount of VOCs. In Table 2, the list of compounds with their retention time (RT) and abundance in arbitrary unit is reported. Correlation coefficient has been calculated to get how similar the two samples were; a value equal to 0.9965 has been obtained. This proves that during the conditioning period of 15 min before fiber exposure in the GC injector, _C. jejuni_ VOCs production was too small to change headspace composition. On the contrary, sample analysis after 20 h has indicated changes in vial headspace due to microorganisms metabolic activity and to slow release of VOCs contained in BHI broth. In Table 3, the list of VOCs is shown. Main differences between the specimens reside in the presence of alcohol compounds, such as 1-pentanol, acetoin, 2,7-dimethyl-4,5-octanediol, 2-propyl-1-pentanol, bicyclo[3.2.1]octan-6-ol, 1-nonanol, \(\gamma\)-methylmercaptoethanolpropyl alcohol and (9E)-9-hexadecen-1-ol greater in _C. jejuni_ samples than control one. This result points out how sugar fermentation \begin{table}
\begin{tabular}{c c c c} \hline \hline
**RT** & **VOC** & \multicolumn{2}{c}{**Abundance**} \\ \hline  & & _Campylobacter_ & Control \\ \hline
1.552 & 3-Butynol & 5,488,041 & 5,289,186 \\
2.674 & Isovaleraldehyde & 28,336,125 & 25,535,856 \\
5.386 & Dimethyl Disulfide & 5,401,037 & 6,048,406 \\
8.666 & 3-O-Methyl-D-frructose & 912,105 & 904,062 \\
9.281 & 1-Hydroperoxyheptane & 533,178 & 418,838 \\
12.332 & 2,5-Dimethylpyrazine & 623,139 & 560,597 \\
14.432 & Nonanal & 512,867 & 227,918 \\
14.624 & 6-Methyloctadecane & 549,617 & 794,739 \\
15.419 & 4-Methyl-2-oxoxvaleric acid & 457,664 & 412,957 \\
15.805 & 2-Acetylamino-3-hydroxy-propionic acid & 27,861 & 51,993 \\
16.017 & 1-(2-Methoxy-1-methylethoxy)-2-propanol & 519,216 & 240,149 \\
16.372 & Ethlyhexanol & 404,819 & 389,367 \\
16.866 & Benzaldehyde & 12,509,648 & 13,515,034 \\
17.430 & 3-Trifluoracetoxydodecane & 92,701 & 168,299 \\
18.455 & 3-Hydroxycyclohexanone & 145,875 & 206,891 \\
18.695 & Acetophenone & 2,201,980 & 1,987,623 \\
19.545 & [(2-Ethlyhexyl)methyl]oxirane & 93,105 & 281,168 \\
19.950 & Methoxy-phenyl-oxime & 1,545,714 & 1,301,333 \\
20.871 & Heptanoic acid & 268,343 & 304,130 \\
21.205 & Benzyl alcohol & 280,516 & 246,860 \\
21.555 & 2-{2-(Benzyloxy)-1-(1-methoxy-1-} \\  & methylethoxy)ethyl]oxirane & 226,967 & 202,114 \\
22.021 & 1-Dodecanol & 222,887 & 482,480 \\
22.465 & Phenyl carbamate & 51,364 & 93,104 \\
23.580 & Octanal & 121,544 & 130,790 \\
24.480 & Octadecanal & 131,841 & 76,150 \\
25.078 & 2,6-Bis(tert-butyl)phenol & 691,529 & 597,086 \\
27.565 & N,N-Dimethylformamide ethylene acetal & 53,073 & 24,830 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: List of volatile organic compounds (VOCs) for _C. jejuni_ and control samples with their retention times (RT) and abundance in arbitrary units at time T0. went on during a 20 h incubation period at 37 \({}^{\circ}\)C. Furthermore, this heating phase could also be responsible for the formation of new compounds derived from pyrazine, like trimethylpyrazine and 2-ethyl-3,6-dimethylpyrazine. In this case, the correlation coefficient is equal to 0.2666, indicating the samples were strongly diverse. Growth of _C. jejuni_ is also confirmed by microbiological analysis. There were (8.57 \(\pm\) 1.18) \(\times\) 10\({}^{4}\) CFU/mL at time T0 in terms of mean \(\pm\) standard deviation calculated on four plates and (1.38 \(\pm\) 0.40) \(\times\) 10\({}^{7}\) CFU/mL at time T20.