# E-Nose Quality Evaluation of Extra Virgin Olive Oil Stored in Different Containers
## 4 Conclusions  
When preserving EVOO at room temperature, the extent of its quality during storage is dependent on the type of container used. EVOO loses its quality after 21 months of storage but remains in a better condition in a tinplate container (EVOO) than in dark glass bottles (VOO or LOO). The oil stored in green PET bottle containers was classified as VOO and in dark glass bottle containers as LOO. However, positive aromas started to be lost in all of them and, therefore, defects related to rancidity appeared. The volatile compounds related to the positive aroma of the oil were: (E)-2-hexenal, (E)-3-hexen-1-ol and (Z)-3-hexen-1-ol, acetate. Those related to negative aromas were hexanal, 2-methyl-2-propanol, and acetic acid. The E-nose differentiated the aroma perceived of the VOO in different groups, demonstrating it to be a powerful tool with analytical capabilities. The results provided by the tasting panel and the volatile compounds profile matched the classification provided by this device. This proves that, combined with chemometric tools, and as an auxiliary tool for a tasting panel, the E-nose represents a fast, simple, reliable, and low-cost method suitable for use at industrial level to control the quality of this product.  
Figure 5: Experimental values against PLS cross-validation predictions (\(\bullet\)) and validation set predictions (\(\times\)) for VOO defects identified by panelists.  
**Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/chemosensors11020085/sl](https://www.mdpi.com/article/10.3390/chemosensors11020085/sl)]([https://www.mdpi.com/article/10.3390/chemosensors11020085/sl](https://www.mdpi.com/article/10.3390/chemosensors11020085/sl)), Table S1:Content of volatile compounds (mean %, n = 3) obtained of VOO packed in different containers during 21 months of storage. R.T.: retention time.  
**Author Contributions:** Conceptualization, E.M.-T., I.D.-M. and D.M.-V.; data curation, J.D.B.-R., J.L. and D.M.-V.; formal analysis, J.D.B.-R., E.M.-T., I.D.-M. and D.M.-V.; funding acquisition, I.D.-M., J.L. and D.M.-V.; investigation, all the authors; methodology, E.M.-T., I.D.-M., J.L. and D.M.-V.; project administration, I.D.-M. and D.M.-V.; resources, I.D.-M. and D.M.-V.; supervision, I.D.-M., J.L. and D.M.-V.; validation, all the authors.; visualization, J.D.B.-R. and D.M.-V.; writing--original draft, J.D.B.-R. and D.M.-V.; writing--review and editing, all the authors. All authors have read and agreed to the published version of the manuscript.  
**Funding:** [PERSON] and [PERSON] wish to thank the Ministerio de Ciencia e Innovacion de Espana (Project PID2020-112996 GB-100 funded by MCIN/AEI/10.13039/501100011033) and Junta de Extremadura (Ayuda a Grupos ref. GR21048 and Project IB20016) co-financed by European Funds for Regional Development. [PERSON] also thanks the Junta de Extremadura (Ayuda a Grupos ref. GR21121) co-financed by European Funds for Regional Development.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The authors confirm that the data supporting the findings of this study are available within the article and the raw data that support the findings are available from the corresponding author, upon reasonable request.  
**Conflicts of Interest:** The authors declare no conflict of interest.