NMR screening of Greek olive oils

Olive oil, obtained from the fruit of Olea europaea, is a highly valuable foodstuff. It constitutes a key agricultural product of the EU market, in particular for the Mediterranean Basin. Olive oil enjoys global recognition for its nutritional value and health-beneficial effects. Therefore appropriate quality control is of major importance. Instrumental analysis plays an important role in the assessment of food authenticity and quality. Particularly, NMR spectroscopy has been used for screening of food and beverages like fruit juices, wine, milk, honey, edible oils, for the identification of impurities and/or biomarkers. In the present study, 273 Greek olive oil samples, originating from two different years of harvest, and several olive varieties from various geographical origins were collected, under standardized conditions, and analyzed with a 400 MHz NMR spectrometer. Standardized conditions were used for sample preparation, which involved the addition of standard amount of solvent and no further pre-treatment. The one-dimensional (1D) NMR spectrum, using multiple suppression plus ¹³C-decoupling, in combination with suitable statistical analysis enabled a classification of olive oils, based on harvest year and variety. In addition, this approach enabled an accurate quantification of characteristic NMR signals. Targeted analysis aiming at the detection of specific marker compounds, belonging mainly to the phenolic fraction, was successfully applied.

Keywords: olive oil, NMR, metabolomics, quantification