Detection of Extra Virgin Olive Oil Adulteration with Lampante Olive Oil and Refined Olive Oil Using Nuclear Magnetic Resonance Spectroscopy and Multivariate Statistical Analysis

Abstract

High-field 31P NMR (202.2 MHz) spectroscopy was applied to the analysis of 59 samples from three grades of olive oils, 34 extra virgin olive oils from various regions of Greece, and from different olive varieties, namely, 13 samples of refined olive oils and 12 samples of lampante olive oils. Classification of the three grades of olive oils was achieved by two multivariate statistical methods applied to five variables, the latter being determined upon analysis of the respective 31P NMR spectra and selected on the basis of one-way ANOVA. The hierarchical clustering statistical procedure was able to classify in a satisfactory manner the three olive oil groups. Subsequent application of discriminant analysis to the five selected variables of oils allowed the grouping of 59 samples according to their quality with no error. Different artificial mixtures of extra virgin olive oil-refined olive oil and extra virgin olive oil-lampante olive oil were prepared and analyzed by 31P NMR spectroscopy. Subsequent discriminant analysis of the data allowed detection of extra virgin olive oil adulteration as low as 5% w/w for refined and lampante olive oils. Further application of the classification/prediction model allowed the estimation of the percent concentration of refined olive oil in six commercial blended olive oils composed of refined and virgin olive oils purchased from supermarkets.

31P NMR spectroscopy in the quality control and authentication of extra‐virgin olive oil: A review of recent progress

“…The application of the statistical method of hierarchical cluster analysis (HCA), and in particular discriminant analysis (DA), to these parameters allowed a good separation of the olive oil samples among these three grades of olive oil. 35 By using the same methodology, mixtures of EVOO with LOO and, in particular, EVOO with ROO can be detected whenever the proportion of LOO and ROO are equal or higher than 5% for both adulterants. 35 In addition, the measurement of the compositional parameters of commercial blended olive oils (legal mixtures of EVOO with ROO) by 31 P NMR spectroscopy, and the calculation of Mahalanobis distances from DA, which measures the distances between each point (sample) and the centroid of each group in a multidimensional space defined by the variables, have led to a semiquantitative estimation of the proportion of added refined olive oil.…”

“…35 By using the same methodology, mixtures of EVOO with LOO and, in particular, EVOO with ROO can be detected whenever the proportion of LOO and ROO are equal or higher than 5% for both adulterants. 35 In addition, the measurement of the compositional parameters of commercial blended olive oils (legal mixtures of EVOO with ROO) by 31 P NMR spectroscopy, and the calculation of Mahalanobis distances from DA, which measures the distances between each point (sample) and the centroid of each group in a multidimensional space defined by the variables, have led to a semiquantitative estimation of the proportion of added refined olive oil. 35 A further application of the NMR methodology to the EVOO authentication is the classification of several edible oils and the detection of EVOO adulteration with refined seed oils.…”

“…35 In addition, the measurement of the compositional parameters of commercial blended olive oils (legal mixtures of EVOO with ROO) by 31 P NMR spectroscopy, and the calculation of Mahalanobis distances from DA, which measures the distances between each point (sample) and the centroid of each group in a multidimensional space defined by the variables, have led to a semiquantitative estimation of the proportion of added refined olive oil. 35 A further application of the NMR methodology to the EVOO authentication is the classification of several edible oils and the detection of EVOO adulteration with refined seed oils. 28 For this purpose, 192 samples of 13 types of edible oils including EVOO were analyzed by employing NMR spectroscopy.…”

Comparison of ¹⁹F and ¹H NMR spectroscopy with conventional methods for the detection of extra virgin olive oil adulteration

“…Extra virgin olive oil (EVOO) is considered to be the highest quality olive oil, in that it does not undergo any treatment other than washing, decantation, centrifugation and filtration. Also, it has an acidity level which is expressed as oleic acid and does not exceed 0.8 % (Fragaki et al, 2005).…”

“…corn, soybean, rapeseed…) added into EVOO (Fragaki et al, 2005;Jafari et al, 2009). In this study, we combined the two groups, using 19 F and 1 H NMR compared with traditional methods (titration and GC-MS) to detect the refined olive oil (ROO) and soybean oil mixed into EVOO.…”