Quantitative 13C NMR method using the DEPT pulse sequence for the determination of the geographical origin (DOP) of olive oils

Nuclear magnetic resonance (NMR) spectroscopy is applied to measure the high-field (500 MHz) C-13 spectra at natural abundance in olive oil samples in order to ascertain the suitability of NMR for discriminating oils from different Italian geographical areas of production and, in particular, from areas labelled with the 'Denomination of Protected Origin' (DOP). The NMR methodology, which uses the distortionless enhancement by polarization transfer (DEPT) pulse sequence for improving the signal-to-noise ratio of C-13 spectra, is optimized for the acquisition, processing and integration parameters to validate the quantitative measurements of the intensities of C-13 resonances of the whole olive oil spectrum. Principal components analysis, which is applied to the C-13 intensity data, correlates the oil samples from the same geographical area provided the composition of the olive oil is monovarietal. The correlation is obtained from properties related to the fatty acid composition of the triglyceride fraction of olive oils. Copyright (C) 2001 John Wiley & Sons, Ltd.