Near infrared Spectroscopy for discrimination between Extra Virgin Olive Oil and Lampante Olive Oil.

The International Olive Oil Council (IOC) has defined standards that can be applied to all the olive oils and olive-pomace oils that are the object of international trade. The IOC recognizes three categories of Virgin olive oils (Extra Virgin, Virgin, and Lampante). Extra Virgin and Virgin Olive Oils (EVOO and VOO) are the most expensive and health promoting of all the categories of olive oils, while Lampante Olive Oil (LOO) is intended for refining or for technical use, not being possible its direct use for human consumption. Despite of the huge amount of efforts invested in research about methods for determining quality, purity and authenticity of Virgin Olive oils and that international standards are used in official inspections by the different producers and importer countries, the adulteration of Extra Virgin Olive oil with other low grade oils remains a major international problem and of enormous media impact. A quick search on Internet using words as “olive oil frauds, adulteration” will bring up to experts and non-experts, a myriad of articles and news, reporting numerous cases of what it is called “Economically-motivated adulteration of EVOO”. However, in our own view, the main reason for recurrent fraud episodes is that inspection bodies are lacking of a suitable and affordable methodology that can help to increase significantly the number of samples inspected per year, providing more evidences than now and exhaustive analytical control is carried out on a large volumen of Olive oils traded at world level.

This paper presents a piece of research done in the framework of a largest project which main goal is to identify an instrumental technology to complement the official method named “Panel Test” for the classification of VOOs . In particular, the present work is aimed to evaluate the potential of the NIR spectroscopy for the discrimination between extra virgin and lampante olive oils. A total of 299 olive oil samples, all of them provided by official inspectors, were used. 189 samples were authenticated by inspectors as Extra Virgin Olive Oil, and 110 samples as Lampante Olive Oil. For collecting NIR spectra, the FNS-6500 SY-II scanning monochromator (spectral range 400-250 nm) was used. Samples were scanned using a folded-transmission gold reflector cup, diameter 3.75 cm, with a pathlength of 0.1 mm, in the transflectance mode. Discriminant models were constructed to classify olive oils by category, using PLS discriminant analysis (PLS-DA). The best models developed correctly classified 92.86% of the samples as EVOO and 80.00% as LOO. A more detailed analysis of the analytical information (i.e., free acidity, peroxide index, extinction coefficients K232 and K270, alkyl and ethyl esters content, moisture and volatile matter content and insoluble impurities in light petroleum content) brings up a very useful information on how to improve the robustness of the discriminant models here developed. The results obtained demonstrate that NIRS technology could be a first-line screening analytical method for inspection laboratories which latter on will only need to analyze for the most costly official methods, the samples detected as “uncertain”.