The authentication and quality assessment of virgin olive oil were performed using high‐resolution 1H and 13C NMR spectroscopy. An overview of the various determinations currently assessed is presented with emphasis on the detection of adulteration with foreign (seed) oils and esterified or refined olive and olive‐pomace oils. Recent results on the NMR analysis of natural compounds (diacylglycerols, free fatty acids, aldehydes, polyphenols, etc.) related to the quality‐freshness of virgin olive oil are also reported. The possible contribution of high‐resolution NMR to the authentication of geographical origin of virgin olive oil is discussed. © 1997 John Wiley & Sons, Ltd.

Based on proton nuclear magnetic resonance (1H-NMR) spectroscopy, a rapid and structure-specific method for the determination of ¢o-3 polyunsaturated fatty acids (PUFAs) in fish lipids is presented. The different chemical shift observed for the methyl resonance of o~-3 PUFAs (d = 0.95 ppm) with respect to the methyl resonance of all other fatty acids (d --0.86 ppm) has provided the possibility of prc~ posing a new and rapid method for the determination of ¢o-3 PUFA content. Twenty-four fish lipid samples (raw, cooked and canned albacore tuna) produced results that showed good agreement between 1H-NMR analysis and gas chromatographic determination. Raw and cooked samples showed significantly higher levels of ¢o-3 PUFA than canned tuna.

High-field (600-MHz) proton nuclear magnetic resonance (1H-NMR) spectroscopy was applied to the analysis of 55 extra virgin olive oil samples from four Italian regions (Campania, Lazio, Sicily, and Umbria) and obtained from diffrent olive varieties. The multivariate statistical analysis (PCA, hierarchical clustering) performed on the normalized intensities of 1H- NMR resonances due to minor components (β-sitosterol, n-alkenals, trans-2-alkenals, and other volatile compounds) allows a good classification of oil samples obtained from traditional varieties with respect to the region of origin (96% of oils correctly classified). Samples obtained from one new experimental cultivar (FS-17) were not correctly classified, indicating a strong contribution of olive variety on the chemical composition of virgin olive oils. The potential contribution and limits of NMR in the authentication of virgin olive oil geographical origin and variety are discussed. Keywords: Proton NMR spectroscopy; virgin olive oil; hierarchical clustering; geographical origin; olive variety; authentication

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The proton NMR characterization of bombesin has been carried out at 500 MHz in DMSO-d, using twodimensional homo-and 'H-'V hetero-correlated techniques. All resonances in the NMR spectra have been assigned and several coupling constants have been measured. The backbone JaCH+,,, coupling constants have constant values that vary between 7.8 and 8.2 Hz and indicate an unfolded structure in DMSO-4. Discrepancies with data recently obtained at 300 MHz [(1987[( ) Eur. J. B&hem. 168, 193-1991