## 3 Results and Discussion
### External Validation of the Instrumental Screening Tool
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Instrumental Screening Tool**} & \multicolumn{3}{c}{**Screening Tool + Reference Method 1**} \\ \hline
**Uncertain Samples 2** & **Samples Assigned to a Category 3** & **Correctly Classified 4 (\% \% of Total Samples)** & **Reliable Assignment (\%)** \\ \hline
**EVOO** & 31.0 & 7.9 & 69.0 & 7.9 & 82.3 & 15.7 & 87.5 & 11.3 \\
**VOO** & 26.0 & 14.4 & 74.0 & 14.4 & 74.6 & 17.2 & 80.5 & 15.5 \\
**LOO** & 6.1 & 6.4 & 93.9 & 6.4 & 80.5 & 9.7 & 83.7 & 9.9 \\ \hline
**Total** & 23.3 & 7.4 & 76.7 & 7.4 & 78.9 5 & 3.83 5 & 84.0 & 4.4 \\ \hline \hline \end{tabular}  
* Considering that the analysis of the uncertain samples by the panel test is 100% of correct classification, given that it is the current reference method; 2 Samples not assigned to a category by the instrumental screening tool; 3 Samples assigned to a category by the instrumental screening tool; 4 % of correctly classified samples = (samples correctly classified/all classified samples) \(\times\) 100; 5 Weighted mean and standard deviation.  
\end{table} 
Table 2: External validation results of the instrumental screening tool (classified correctly and uncertain samples for EVOO (\(n\) = 24), VOO (\(n\) = 22) and LOO (\(n\) = 14) samples) and the final reliable assignment considering the screening tool’s plus the panel test’s classification results. the instrumental screening tool and the panel evaluation, with a panel workload reduction to one-third of the total sampling. Therefore, the classification rate obtained by the present strategy is comparable to those obtained by other approaches [11; 12; 13; 15; 16; 21], but it is based on a simple, relatively fast, automatable and widespread technique. As it has been mentioned above, misalignments can sometimes occur between different panels. Here, a group of 24 VOO and LOO samples were reported as boundary by the sensory panels' coordinator because initially there was a lack of agreement among the panels and they needed a formative reassessment after which a consensus was reached [5]. In other studies, olive oils are submitted to a single panel that determines their category. Since this category is taken as definite, any error or misalignment would affect the identity of the samples and model development and validation. However, we were able to detect these boundary samples thanks to the joint work of the six sensory panels, which allowed us to obtain more reliable results, as we could be sure that the category of the samples had been correctly assigned by the panels. To understand how these boundary samples influenced the classification efficiency of the instrumental screening method, we examined the identity of the misclassified and uncertain samples during model external validation. We observed that several of the VOO and LOO that were misclassified or identified as uncertain in any of the sets of the validation step pertained to this boundary group: main perceived defect (MPD) fusty-musty: samples 187, 190, 285 and 290; MPD musty-humid-earthy: samples 286 and 289; MPD rancid: samples 189, 192, 193, 287, 288 and 301, Supplementary Material (Table S1). Interestingly, 12 out of those 24 boundary oils were correctly classified by the instrumental method according to the reassessment panel's results. This fact highlights the great support that the instrumental screening tool would provide to the sensory panel also in case of boundary samples. Moreover, to ascertain the role of the type of sensory defect in classification efficiency, we investigated whether the successfulness of the classification depended on the presence of a given defect in a sample. Table 3 shows the results of the external validation of VOO and LOO samples according to their MPD (rancid, fusty-muddy or musty-humid-earthy). According to the global results of Table 3, the highest uncertainty rate was found for VOO and LOO samples whose MPD was rancid, which also had a lower classification rate.