Integrated NMR-based profiling and HPLC-DAD analysis for Extra Virgin Olive Oil (EVOO) authentication assessment

Extra Virgin Olive Oil (EVOO) possesses a high-value rank in the food industry, thus making it a common target for adulteration [1]. Therefore, several methods have been made available over the years. However, the issue of authentication remains unresolved with several national food safety organizations struggling to choose the most reliable one. Over the course of this study, the aim was to determine the origin of EVOOs suggesting a fast method that could easily be adopted. An established HPLC-DAD method focusing on EVOO polyphenols was used to reinforce the NMR based metabolic profiling.

Samples from three Mediterranean countries, Spain, Italy and Greece, as well as blended samples were analyzed with HR-NMR spectroscopy and with HPLC-DAD after hydrolysis aiming to quantitate both free and bound forms of hydroxytyrosol (HT) and tyrosol (T). The NMR spectra were recorded, preprocessed and underwent multivariate statistical analysis leading to the discovery of certain biomarkers related to the classification of the samples based on their geographic origin. In addition to the exploitation of the entire oil’s composition, statistical correlations were made between the NMR metabolite profiling and HPLC quantitative data of HT and T which are also related to the health claim issued by EFSA [2].

In conclusion, EVOO was classified according to its origin using NMR spectroscopy and was combined for the first time with a more established method in food analysis, that is HPLC-DAD. Finally, specific biomarkers were identified (i.e. aldehydic derivatives of the hydroxytyrosol and tyrosol moiety, like oleacein and oleocanthal, and triterpenoids such as cycloartenol), which are characteristic of each geographic origin.

S. Beteinakis wishes to thank the IKY foundation. The authors are grateful to the EU Programme ‘Olive-Net’.

• References

• 1 Dais P, Hatzakis E. Quality Assessment and Authentication of Virgin Olive Oil by NMR Spectroscopy: A Critical Review. Anal. Chim. Acta 2013; 765: 1-27.
• 2 EFSA, Scientific Opinion. EFSA J , 2011; 9 (04) 2033.