## 3 Results and Discussion
### Volatile Compounds (VCs)  
The VCs of the oil produced from the control olives and the olives treated with CO\({}_{2}\) were examined. In Figure 3, typical chromatograms of the VCs are presented, while in Table 2, a comparison of the analyses among the three oils (from CO\({}_{2}\) treated and control olives, and commercial oil) is presented. \begin{table}
\begin{tabular}{c c c} \hline
**Sensory Attributes** & **Olives (Control)** & **Olives (CO\({}_{2}\))** \\ \hline Overall acceptability 1  & 2 (1.0) & 8 (0.0) \\ Bitterness 2  & 9 (0.0) & 3 (1.0) \\ Overall preference 3  & 0 & 7 \\ \hline \end{tabular}
\end{table} 
Table 1: Sensory assessment of olives stored under a CO\({}_{2}\) atmosphere and regular atmospheric conditions (control). \begin{table}
\begin{tabular}{c c c c c c} \hline
**No.** & **VCs** & **CAS** & **RT 1 ** & **Olive Oil** & **Olive Oil** & **Olive Oil** \\  & & & **(Commercial)** & **(Control)** & **(CO\({}_{2}\))** \\ \hline
1. & Ethanol & 64-17-5 & 2.751 & ND 2  & ND & 50.75 (2.07) 1  \\
2. & _n_-Decane & 124-18-5 & 3.763 & ND 2  & ND & 1.75 (0.05) & ND \\
3. & _n_-Undecane & 1120-21-4 & 4.014 & ND 2  & ND & 0.71 (0.08) & ND \\ \hline \end{tabular}
\end{table} 
Table 2: VCs of olive oils. Figure 3: Typical GC-MS chromatogram of the VCs from olive oil storage under CO\({}_{2}\) atmosphere (red chromatogram) and control sample (blue chromatogram). In total, 30 different VCs, were detected. A total of 18 of them (which account for 83.87 \(\pm\) 0.60% of the total VCs) were identified in the CO\({}_{2}\) atmosphere processed sample, followed by 13 in the control (64.83 \(\pm\) 2.21% of the total VCs) and 11 in the sample of commercial olive oil (56.55 \(\pm\) 1.76% of the total VCs). In all cases, aldehydes such as hexanal and \(E\)-hex-2-enal and alcohols such as \(Z\)-2-hexen-1-ol and \(Z\)-3-hexen-1-ol made up the majority of the C\({}_{6}\) VCs that were found. The primary VCs found were C\({}_{6}\) compounds, which are produced when linoleic or \(\alpha\)-linolenic acids are oxidized under the action of LOX [14]. Variable acyl hydrolase activity and, as a result, good or poor availability of free polyunsaturated fatty acids could be the cause of the different values of C\({}_{6}\) aldehydes found in samples. The oil produced from control olive was characterized by the highest level of hexanal (24.09 \(\pm\) 1.44%), and \(Z\)-3-hexen-1-ol (3.22 \(\pm\) 0.40%). The total C\({}_{6}\) VCs were 42.93 \(\pm\) 2.89% (66.22 \(\pm\) 2.10% of total VCs), and the total C\({}_{5}\) VCs were 0.69 \(\pm\) 0.12% (1.06 \(\pm\) 0.21% of total VCs). Compared to the other samples, \(Z\)-2-Penten-1-ol was detected only in the control oil (0.69 \(\pm\) 0.12%). In addition, an aromatic heterocyclic compound, methoxy-phenyl-oxime, was detected only in oil produced from control olive at 1.77 \(\pm\) 0.08% (its appearance in virgin olive oil was reported earlier [11]). Methoxy-phenyl-oxime is formed during the growth process (fermentation) of _Soranguium cellulosum_, a Gram-negative bacterium of the group myxobacteria [33]. Myxobacteria, which are primarily found in soil, create compounds with known antineoplastic activity [11]. The majority of the hydrocarbons  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**No. **} & \multirow{2}{*}{**VCs**} & \multirow{2}{*}{**CAS**} & \multirow{2}{*}{**RT a**} & \multicolumn{3}{c}{**Peak Area (\%)**} \\ \cline{5-6}  & & & **Number** & & **Olive Oil** & **Olive Oil** & **Olive Oil** \\  & & & & **(Commercial)** & **(Control)** & **(CO\({}_{2}\))** \\ \hline
4. & Hexanal c [FOOTNOTE:c]Footnote c: Values are the mean of triplicate determinations. Standard deviation is given in parentheses; a Retention time (min); b Not detected; c [FOOTNOTE:c]Footnote c: Values are the mean of triplicate determinations. in the waxes that cover olive fruits and leaves are \(n\)-alkanes. They limit water loss and decrease the cuticle's ability to become wet [34].