Quality Assessment of Olive Oil by 1H-NMR Fingerprinting (original) (raw)
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Quality assessment and authentication of virgin olive oil by NMR spectroscopy: A critical reviewt
Analytica Chimica Acta, 2013
Nuclear Magnetic Resonance (NMR) Spectroscopy has been extensively used for the analysis of olive oil and it has been established as a valuable tool for its quality assessment and authenticity. To date, a large number of research and review articles have been published with regards to the analysis of olive oil reflecting the potential of the NMR technique in these studies. In this critical review, we cover recent results in the field and discuss deficiencies and precautions of the three NMR techniques (1H, 13C, 31P) used for the analysis of olive oil. The two methodological approaches of metabonomics, metabolic profiling and metabolic fingerprinting, and the statistical methods applied for the classification of olive oils will be discussed in a critical way. Some useful information about sample preparation, the required instrumentation for effective analysis, the experimental conditions, and data processing for obtaining high-quality spectra will be presented as well. Finally, constructive criticism will be exercised on the present methodologies used for the quality control and authentication of olive oil.
1H and13C NMR of virgin olive oil. An overview
Magnetic Resonance in Chemistry, 1997
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 esteriÐed or reÐned 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.
1H-NMR fingerprinting to evaluate the stability of olive oil
Food Control, 2011
a b s t r a c t 1 H-NMR fingerprinting is used to evaluate the stability of olive oil at room temperature while protected from light. Principal component analysis (PCA) of the 1 H-NMR spectral data allows to visualize the evolution of virgin olive oil (VOO) with time. The PCA loadings disclose the chemical compounds responsible for the compositional changes taking place in VOO. None of the 1 H-NMR signals present at time zero disappeared or experienced significant decreases or increases within the 3 years and seven months of the study. However, some small changes in the signals, and the appearance of some low intensity ones, indicate that some oxidative and hydrolytic degradation of the VOO started after one year. The presence of 1 H-NMR signals of hydroperoxides (primary oxidation products) with relative small intensities indicates that the oxidative degradation was taking place at a very low rate and yield. Moreover, the characteristic resonances of aldehydes (main secondary oxidation products) were not detected in the VOO over the studied time period, therefore the secondary oxidation process had not yet occurred. These results confirm the high oxidative stability of VOO at room temperature. On the other hand, slight changes in the 1 H-NMR signal intensity of tryglycerides and sn-1,3-diglycerides indicates that some hydrolytic degradation of the VOO had started.
Foods
This work encompasses the use of 1D multinuclear NMR spectroscopy, namely, 1H NMR and 13C NMR DEPT 45, combined with a multivariate statistical analysis to characterize olive oils produced from nine different varieties: Galega Vulgar, Cobrançosa, Cordovil de Serpa, Blanqueta, Madural, Verdeal Alentejana, Arbequina, Picual and Carrasquenha. Thus, the suitability of an NMR-based spectroscopic tool to discriminate olive oils according to their varietal origin is addressed. The results obtained show that the model based on 13C NMR DEPT 45 data has a stronger performance than the model based on 1H NMR data, proving to be promising in the discrimination of the olive oils under study based on their varietal origin, being particularly relevant for olive oils of the Galega Vulgar variety.
Journal of agricultural …, 2007
The present study was designed to assess the agreement between analytical methodologies based on 1 H and 31 P NMR spectroscopy and conventional analytical methods (titration, gas chromatography, and high performance liquid chromatography) for measuring certain minor and major constituents (free acidity, fatty acids, iodine value, and phenolic compounds) of olive oil. The standard deviations of the NMR method were comparable to those of the conventional methods, except perhaps those of the total hydroxytyrosol and total tyrosol. Linear regression analyses showed strong correlations between NMR and conventional methods for free acidity, total hydroxytyrosol, total tyrosol, total diacylglycerols, (+)-pinoresinol, (+)-1-acetoxypinoresinol, and apigenin; good correlations for linoleic acid, free hydroxytyrosol, and free tyrosol; and weak correlations for oleic acid, linolenic acid, saturated fatty acids, and luteolin. Furthermore, a method comparison study was conducted and the agreement between NMR and conventional methods was evaluated by using the Bland and Altman statistical analysis. The distribution of the data points in the bias plot showed that 96.4% and 100% of the measurements of free acidity and iodine value, respectively, were within the limits of agreement of the two methods. For the remaining constituents of olive oil, the percentage of measurements, located within the limits of agreement, ranged from 94% to 98.5%.
Extra-Virgin Olive Oils from Nine Italian Regions: An 1H NMR-Chemometric Characterization
Metabolites
Extra-virgin olive oil (383 samples; EVOOs) of three consecutive harvesting years from nine Italian regions were collected and submitted to an 1H NMR-chemometric protocol to characterize the samples according to their origin (geographical area and variety). A more complete assignment of the olive oil 1H spectrum in CDCl3 and DMSOd6 was reported identifying 24-methylencycolartanol. A single classification model provided the discrimination of EVOOs among the three geographical macro-areas (North, Islands, Center-South), whereas a hierarchical approach based on breaking the overall classification problem into a series of smaller linear discriminant analysis (LDA) sub-models was tested to differentiate olive oils according to their geographical regions. Specific compounds responsible for olive oil characterization were identified.
Journal of Agricultural and Food Chemistry, 2007
The present study was designed to assess the agreement between analytical methodologies based on 1 H and 31 P NMR spectroscopy and conventional analytical methods (titration, gas chromatography, and high performance liquid chromatography) for measuring certain minor and major constituents (free acidity, fatty acids, iodine value, and phenolic compounds) of olive oil. The standard deviations of the NMR method were comparable to those of the conventional methods, except perhaps those of the total hydroxytyrosol and total tyrosol. Linear regression analyses showed strong correlations between NMR and conventional methods for free acidity, total hydroxytyrosol, total tyrosol, total diacylglycerols, (+)-pinoresinol, (+)-1-acetoxypinoresinol, and apigenin; good correlations for linoleic acid, free hydroxytyrosol, and free tyrosol; and weak correlations for oleic acid, linolenic acid, saturated fatty acids, and luteolin. Furthermore, a method comparison study was conducted and the agreement between NMR and conventional methods was evaluated by using the Bland and Altman statistical analysis. The distribution of the data points in the bias plot showed that 96.4% and 100% of the measurements of free acidity and iodine value, respectively, were within the limits of agreement of the two methods. For the remaining constituents of olive oil, the percentage of measurements, located within the limits of agreement, ranged from 94% to 98.5%.
Foods
The application of 1H and 13C nuclear magnetic resonance (NMR) in conjunction with chemometric methods was applied for the discrimination and authentication of Maltese extra virgin olive oils (EVOOs). A total of 65 extra virgin olive oil samples, consisting of 30 Maltese and 35 foreign samples, were collected and analysed over four harvest seasons between 2013 and 2016. A preliminary examination of 1H NMR spectra using unsupervised principle component analysis (PCA) models revealed no significant clustering reflecting the geographical origin. In comparison, PCA carried out on 13C NMR spectra revealed clustering approximating the geographical origin. The application of supervised methods, namely partial least squares discriminate analysis (PLS-DA) and artificial neural network (ANN), on 1H and 13C NMR spectra proved to be effective in discriminating Maltese and non-Maltese EVOO samples. The application of variable selection methods significantly increased the effectiveness of the dif...