Extra virgin olive oil: Portugese olive oil omics for authenticity

An image of extra virgin olive oil

Researchers from Evora University presents one of their projects on extra virgin olive oil, which is designed to ensure authenticity and traceability.

Currently, food authenticity and traceability are considered emerging topics in food science. The interest of the scientific community has been widening to encompass consumers, the food industry, and regulators. Specifically, the assessment of food authentication is crucial to evaluate the occurrence of fraudulent practices, and their implementation enables to ensure the genuineness of food products. However, the development of reliable analytical quality certification tools to assess food authentication is a challenging task.

Traditional strategies to assess food authentication rely on the identification of a chemical marker compound(s), followed by it quantification and the comparison of the obtained values with those established for genuine material. Despite the suitability of this approach, its applicability is limited and implies a previous identification of the target molecule (marker). Moreover, owing to the multidisciplinary character of authentication issues, the development of analytical tools that enable this question to be fully addressed must include a more comprehensive approach based on analytical fingerprinting and profiling, and that can be achieved by a metabolomics and a genomic approach.

Why the focus on extra virgin olive oil?

Mediterranean countries are well known for the production of olive oils (OO), one of the oldest vegetable oils, and a major constituent of the Mediterranean diet. Since extra virgin olive oil has a relatively higher price on the market, it is becoming mandatory to establish OO authenticity and detect possible adulterations, which allows the protection of both producers and consumers.

The characterisation of the geographical origin of extra virgin olive oil, which is permitted to be marketed under a protected designation of origin (PDO) or protected geographical indication (PGI) label, based on their area, cultivars and methods of production, is becoming increasingly important. As can be expected, given the financial benefits associated with these prestigious labels, it is very likely that economic fraud occurs. Therefore, analytical methods are necessary to guarantee the authenticity and traceability of PDO and PGI olive oils to prevent illicit practices.

The aim of PDO is to add value to certain specific high-quality products from a particular origin, and in order to ensure that, tools must be available to warranty geographical and varietal assessment of extra virgin olive oils. These tools can also be used to discriminate among organic and nonorganic extra virgin olive oil, since organic products are gaining importance in the market and it is becoming mandatory to assess the authenticity of these OO.

What analytical techniques are we using?

Major and minor compounds in extra virgin olive oil have been used as traceability markers of OO. Olive oils markers for authenticity and adulterations are usually achieved by determination of volatile compounds, phenolic compounds, tocopherols, pigments, sterols, fatty acids and triacylglycerols, as well as by sensorial analysis, although several limitations can be drawn to the use of these techniques.

The volatile composition of varietal extra virgin olive oils is being assessed by head space solid phase microextraction coupled to gas chromatography with mass detection (HS-SPME-GC/MS). This technique allowed us to establish each cultivar volatile profile. it was carried out a molecular and chemometric analysis of the chromatographic data obtained using an updated surface density van Krevelen graphical statistic method.

Spectroscopy techniques, such as NMR and IR, are becoming increasingly more useful to assess OO authenticity. Vibrational spectroscopy is a non-invasive fingerprinting method that allows rapid and nondestructive analysis. In this approach, we have developed a rapid method for the evaluation of fatty acids of monovarietal Portuguese extra virgin olive oils based on Fourier-transform near-infrared spectroscopy (FT-NIRS). Nuclear Magnetic Resonance (NMR) Spectroscopy has been extensively used for the analysis of olive oil, constituting a valuable tool particularly for the study of the triacylglycerol fraction, which is the major fraction of OO. Thus, within this project we have explored the usefulness of one-dimensional NMR spectroscopy (1H and 13C NMR) for the assessment of the triacylglycerol fraction of OO.

The assessment of stable isotope composition of light elements by isotope ratio mass spectroscopy (IRMS) is also a resourceful technique to be used not only for geographic authenticity but also for discriminate organic OO. Single-isotope or multi-isotope ratios analysis of the most abundant light elements in food (δ 13C, δ 2H, and δ 18O) can provide a fingerprint that reflects both geo-climatic characteristics of the area of production, as well as the local agricultural practices.

Two approaches are being used: bulk analysis and compound-specific isotope analysis (CSIA). In fact, a more accurate approach to the isotope analysis of the bulk samples is the analysis of individual compounds. CSIA techniques provide a more in-depth understanding of the mechanisms involved adding further information to improve geographical discrimination of olive oils.

Focusing on Portuguese cultivars

Our research at Evora University is focused on some Portuguese cultivars such as Galega Vulgar, Carrasquenha, Cordovil de Serpa, Cobrançosa, Blanqueta de Elvas, Madural, and Verdeal Alentejana, which are also the ones responsible for the generation of extra virgin olive oil under the classification of PDO. But with the huge increase of olive orchard areas, namely in Alentejo, nontraditional cultivars are gaining more importance and only the deep knowledge of our varieties and the quality of our olive oils can hopefully contribute to increasing the representativity of Portuguese cultivars in new orchards in Portugal.

Acknowledgements
Funding provided by PTDC/AGR/2003/2014.

Professor Maria João Cabrita
ICAAM, Universidade de Évora,
+35 1 266 760800/69
mjbc@uevora.pt
Tweet @univdeevora
www.uevora.pt/pessoas/(id)/17090

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