# Microbiota and Metabolite Profiling of Spoiled Spanish-Style Green Table Olives
## Results and Discussion
### Evaluation of Sensory Data  
Based on the above-mentioned PCA results, 2 or 3 representatives of each group/subgroup were selected for sensory evaluation using the descriptors \"zapatera\", \"butyric\", and \"putrid\". The mean scores for these spoilage descriptors are shown in Table 4.  
All samples had 1 or 2 spoilage descriptors with scores higher than the control sample. For the zapatera descriptor, all the samples except MFL1 and MCL2 had higher scores in comparison with the control. Samples GFC1, MFL1, and MCL2 had higher scores than the control for the butyric descriptor. However, the putrid perception was not noted in any of the samples. Therefore, only the sensory descriptors \"butyric\" and \"zapatera\" appeared to be adequate to characterize the spoiled samples.  
In order to reveal relationships between these descriptors (Y variables) and volatile metabolites (X variables), individual PLS analyses were carried out (Figure 6).  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & & & & & & & & \\ \hline
**Descriptor** & **GFC1** & **GFL1** & **GCC1** & **GCL2** & **MFC2** & **MFL1** & **MCC2** & **MCL2** & **M1 (control)** \\ \hline Zapatera & 5.7 \(\pm\) 0.7 * & 5.0 \(\pm\) 0.6 * & 4.9 \(\pm\) 0.6 * & 4.6 \(\pm\) 0.6 * & 5.3 \(\pm\) 0.5 * & 4.3 \(\pm\) 0.5 & 5.0 \(\pm\) 0.5 * & 3.6 \(\pm\) 0.4 & 2.4 \(\pm\) 0.4 \\ Butyric & 4.5 \(\pm\) 0.6 * & 3.7 \(\pm\) 0.6 & 2.7 \(\pm\) 0.4 & 3.4 \(\pm\) 0.5 & 3.5 \(\pm\) 0.5 & 4.6 \(\pm\) 0.7 * & 2.5 \(\pm\) 0.3 & 4.3 \(\pm\) 0.6 * & 2.3 \(\pm\) 0.3 \\ Putrid & 2.8 \(\pm\) 0.4 & 2.7 \(\pm\) 0.5 & 3.0 \(\pm\) 0.5 & 3.1 \(\pm\) 0.6 & 2.3 \(\pm\) 0.4 & 2.6 \(\pm\) 0.5 & 2.0 \(\pm\) 0.3 & 2.7 \(\pm\) 0.4 & 1.4 \(\pm\) 0.2 \\ \hline \multicolumn{8}{c}{Values are the mean (\(\pm\) standard error) scores from 15 panelists with 2 replications (n = 30). For a given descriptor, an asterisk denotes that the mean value is significantly different from the control sample at the 0.05 level according to [PERSON]’s \(t\)-test. See Table 5 for the meanings of samples abbreviations.} \\ \end{tabular}
\end{table}
Table 4: The intensity ratings for the sensory spoilage descriptors of olive brines.  
The VIP (variable importance on projection) plots showing the important and significant X variables for butyric and zapatera descriptors are presented in Figure S4. Variables with VIP \(>\)1 are the most relevant for explaining the sensory spoilage descriptors. The main contributors to the butyric off-odor model were benzyl pentanoate, butyric acid, nonanal, valeric acid, 1-propanol, dimethyl sulfide, methyl pentanoate, (\(Z\))-3-hexen-1-ol, phenylethyl alcohol, methyl hexanoate, and octanal. It is worth noting that a significant correlation between the butyric descriptor and butyric acid was found. This is not surprising, as this acid is the \"character impact compound\" of butyric spoilage. However, it must be pointed out that the number of samples used in the PLS analysis was small and when this fact occurs often makes it difficult to associate a single compound with a single sensory attribute, even if a relationship is known [36]. In the case of the zapatera descriptor, propionic acid, methyl propanoate, propyl propanoate, acetic acid, 3-methyl-1-pentanol, 1-octanol, \(\alpha\)-terpineol, 1-butanol,  
Figure 6: The PLS regression between the volatile metabolites and sensory spoilage descriptors: (**a**) butyric off-odor and (**b**) zapatera off-odor.  
and cyclohexanoic acid were the main contributors to the zapatera model. Cyclohexanoic acid, which is used as the reference material for the zapatera descriptor, as mentioned above, is included among the important contributors to the zapatera off-odor.