## 3 Results
### Chemical Identification and Semi-Quantification
#### 3.1.3. Inoculated Fruits  
Variations in MVOC profiles were also measured from different inoculated fruits. Overall, 42.33% of the variation in the chemical composition is explained by the chosen potential explanatory variables (i.e., bacteria strain, collection methods, type of fruits, and post-inoculation time). MVOCs were detected in apples, kiwifruit, and oranges at 24 h post-inoculation, using both Tenax(r) and SPME. Multivariate analysis revealed a clear separation between Tenax(r) and SPME extracts collected at 24 h post-inoculation in apples, kiwifruit, and oranges (ANOSIM; R = 0.19, \(p\) = 2e-04; Figure 2). A total of seven compounds were significantly associated with Tenax(r) (i.e., two alcohols, one aldehyde, one aromatic, two hydrocarbons, and two terpenes; Table 3). In line with the previously mentioned variations associated with detection methods, eight compounds, which included indole and 2-phenylethanol, were significantly associated with SPME (Table 3). Figure 1: Relative peak area (i.e., total area under the compound peak over the total peak areas from all compounds within a sample) of a selection of antennally active compounds produced by four bacteria and collected by solid phase micro-extraction (SPME). CF, _Citrobacter freundii_; EC, _Enterobacter cloacaae_; KO, _Klebsiella oxytoca_; PA, _Enterobacter_ (syn. _Pantoa_) _agglomerans_. Figure 2: Nonmetric multidimensional scaling (NMDS) plot (stress = 0.107) of the chemical composition of three fruits (apples, kiwifruit, and oranges) and un-inoculated fruits (control). Each point represents a Tenax® (solid)- or SPME-extract sample. The color of the points encodes for the bacterial strains, and the shape encodes for the incubation time prior odor collection. CF, _Citrobacter freundii_; EC, _Enterobacter cloace_; KO, _Klebsiella axytoca_; PA, _Enterobacter_ (syn. _Pantoea) agglomerans_. Centroids of the clusters of each fruit are represented by ellipses (standard deviation in gray). Volatile profiles are significantly different between fruits (ANOSIM, R = 0.5032, \(p\) = 1e-04), and the collection methods (ANOSIM; R = 0.19, \(p\) = 2e-04). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**Compound**} & \multicolumn{2}{c}{**AnNOSIM Statistics**} & \multicolumn{2}{c}{**Group Age**} \\ \cline{3-5} \multicolumn{1}{c}{**Compound**} & \multicolumn{2}{c}{**Functional Class**} & \multicolumn{2}{c}{**AnNOSIM Statistics**} \\ \cline{3-5} \multicolumn{1}{c}{**Indole**} & \multicolumn{1}{c}{**Aromatic**} & \multicolumn{1}{c}{0.499} & \multicolumn{1}{c}{0.0088 **\({}^{**}\)**} \\ \hline \(\beta\)-Pinene & Terpene & 0.479 & 0.0147 \({}^{*}\) \\ \hline \(\operatorname{Phenylethyl alcohol}\) & Alcohol & 0.448 & 0.0063 \({}^{**}\) \\ \hline \(\operatorname{Caryophyllene}\) & Terpene & 0.446 & 0.0155 \({}^{*}\) \\ \hline \(\operatorname{D-Limonene}\) & Terpene & 0.436 & 0.0362 \({}^{*}\) \\ \hline \(\operatorname{Methyl octaoate}\) & Ester & 0.43 & 0.0274 \({}^{*}\) \\ \hline \(\operatorname{Naphtalene}\) & Hydrocarbon & 0.427 & 0.0155 \({}^{*}\) \\ \hline \(\operatorname{Ethyl octaoate}\) & Ester & 0.418 & 0.0292 \({}^{*}\) \\ \hline \multicolumn{2}{c}{**Compound**} & \multicolumn{2}{c}{**AnNOSIM statistics**} \\ \cline{3-5} \multicolumn{1}{c}{**Compound**} & \multicolumn{2}{c}{**Functional class**} & \multicolumn{1}{c}{R value} & \multicolumn{1}{c}{\(p\)-value} \\ \hline \(\operatorname{(E)-2-Nonen-1-ol}\) & Alcohol & 0.598 & 0.0003 \({}^{***}\) \\ \hline \end{tabular}
\end{table} 
Table 3: List of individual compounds that are significantly associated with different types of fruits: apple, kiwifruit, and oranges (ANOSIM, R = 0.5032, \(p\) = 1e-04); collection methods: Tenax® filter and SPME fiber (ANOSIM; R = 0.19, \(p\) = 2e-04); and incubation times: 24 h, 72 h, and 5 days post-inoculation (ANOSIM; R = 0.385, \(p\) = 0.007). Statistical significance: \(p\leq 0.05\) (*), \(p\leq 0.01\) (**), \(p\leq 0.001\) (***).