Sensitivity of Proton NMR Relaxation and Proton NMR Diffusion Measurements to Olive Oil Adulterations with Vegetable Oils

Abstract

Olive oils and, in particular, extra-virgin olive oils (EVOOs) are one of the most frauded food. Among the different adulterations of EVOOs, the mixture of high-quality olive oils with vegetable oils is one of the most common in the market. The need for fast and cheap techniques able to detect extra-virgin olive oil adulterations was the main motivation for the present research work based on 1H NMR relaxation and diffusion measurements. In particular, the 1H NMR relaxation times, T 1 and T 2, measured at 2 and 100 MHz on about 60 EVOO samples produced in Italy are compared with those measured on four different vegetable oils, produced from macadamia nuts, linseeds, sunflower seeds, and soybeans. Self-diffusion coefficients on this set of olive oils and vegetable oil samples were measured by means of the 1H NMR diffusion ordered spectroscopy (DOSY) technique, showing that, except for the macadamia oil, other vegetable oils are characterized by an average diffusion coefficient sensibly different from extra-virgin olive oils. Preliminary tests based on both NMR relaxation and diffusometry methods indicate that eventual adulterations of EVOO with linseed oil and macadamia oil are the easiest and the most difficult frauds to be detected, respectively.

Rapid Identification of Adulteration in Edible Vegetable Oils Based on Low-Field Nuclear Magnetic Resonance Relaxation Fingerprints

“…These issues can be potentially addressed by low-field NMR (LF-NMR) spectroscopy, which has been widely used as a powerful analytical tool in food analysis for quality monitoring and process supervision [ 17 , 18 , 19 , 20 ]. For example, Ancora et al [ 21 ] demonstrated that LF-NMR relaxation measurements could be applied to determine the occurrence of adulteration in EVOO samples when mixed with four different edible vegetable oils. Moreover, Wang et al [ 22 ] applied this methodology to detect the adulteration of sesame oil samples with soybean oil, and the adulteration ratios were estimated using principal component analysis (PCA) and partial least squares (PLS).…”

Semi-Autonomic AI LF-NMR Sensor for Industrial Prediction of Edible Oil Oxidation Status

“…An important material characterization is the self-diffusion coefficient, D, that is determined by the 1 H LF-NMR pulsed-field gradient spin echo (PFGSE) method [ 38 ], which is well accepted for characterizing 1 H mobility based on the chemical and physical status of edible oil with fatty acids and esters [ 39 , 40 ]. Using D values of intact LSO and thermal oxidized samples, the pattern of mobility changes occurring during LSO oxidation could be monitored with a very good correlation between coefficient D and conventional wet chemistry standard tests of oil oxidation based on PV, p -AV, and TOTOX [ 41 ].…”

Rapid Identification of Adulteration in Extra Virgin Olive Oil via Dynamic Headspace Sampling and High-Pressure Photoionization Time-of-Flight Mass Spectrometry

“…Olive oil is highly appreciated worldwide owing to its unique organoleptic properties (taste/flavor) as well as abundant nutritional values toward human health . Being the top qualified product in all olive oil grades, extra virgin olive oil (EVOO) usually has a higher price compared to others, which inevitably makes itself a target of adulteration . Adulteration of EVOO with low-cost edible oils (e.g., hazelnut, corn, peanut, and rapeseed oils) is a quite common fraudulent practice and has become a serious problem all over the world .…”

“…1 Being the top qualified product in all olive oil grades, extra virgin olive oil (EVOO) usually has a higher price compared to others, which inevitably makes itself a target of adulteration. 2 Adulteration of EVOO with low-cost edible oils (e.g., hazelnut, corn, peanut, and rapeseed oils) is a quite common fraudulent practice and has become a serious problem all over the world. 3 The economically motivated EVOO adulteration not only infringes customer rights but may also lead to serious allergies and threat to human health.…”