Use of high-resolution C-13 nuclear magnetic resonance spectroscopy for the screening of virgin olive oils

C-13 Nuclear magnetic resonance (NMR) spectra of 104 oil samples were obtained and analyzed in order to study the use of this technique for routine screening of virgin olive oils. The oils studied included the following: virgin olive oils from different cultivars and regions of Europe and north Africa, and refined olive, lampante olive, refined olive pomace, high-oleic sunflower, hazelnut, sunflower, corn, soybean, rapeseed, grape seed, and peanut oils, as well as mixtures of virgin olive oils from different geographical origins and mixtures of 5-50% hazelnut oil in virgin olive oil. The analysis of the spectra allowed us to distinguish among virgin olive oils, oils with a high content of oleic acid, and oils with a high content of linoleic acid, by using stepwise discriminant analysis. This parametric method gave 97.1% correct validated classifications for the oils. In addition, it classified correctly all the hazelnut oil samples and the mixtures of hazelnut oil in virgin olive oil assayed. All of these results suggested that C-13 NMR may be used satisfactorily for discriminating some specific groups of oils, but to obtain 100% correct classifications for the different oils and mixtures, more information than that obtained from the direct spectra of the oils is needed.