Near UV-Vis and NMR Spectroscopic Methods for Rapid Screening of Antioxidant Molecules in Extra-Virgin Olive Oil

Abstract

Several spectroscopic techniques have been optimized to check extra-virgin olive oil quality and authenticity, as well as to detect eventual adulterations. These methods are usually complementary and can give information about different olive oil chemical components with bioactive and antioxidant properties. In the present work, a well-characterized set of extra-virgin olive oil (cultivar Frantoio) samples from a specific area of Tuscany (Italy) were investigated by combining near UV-Vis absorption spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) to identify and quantify different chemical components, such as pigments, secoiridoids and squalene, related to the nutritional and quality properties of olive oils. Moreover, the pigmentation index of olives, organoleptic and sensory properties, total phenolic compound contents and the lipidic fractions of olive oils were investigated. The results obtained are, finally, compared and discussed in order to correlate several properties of both olives and olive oils with specific features of the cultivation area.

Study of the Evolution of Pigments from Freshly Pressed to ‘On-the-Shelf’ Extra-Virgin Olive Oils by Means of Near-UV Visible Spectroscopy

“…These further experiments used to test and validate the spectroscopic method allowed us to determine the kinetic constants of both chlorophyll a and pheophytin a degradation in EVOOs stored in optimal conditions, confirming previous studies of kinetics of pigments in EVOOs [26,58]. The ability of the implemented spectroscopic method to evaluate the concentration of both chlorophylls and pheophytins is particularly interesting if we consider that in most of the cases actual spectroscopic methods [28,29,50] allow one to quantify only the total of chlorophylls' derivatives and not the single components. This spectroscopic method is relatively easy to use and it combines the advantage of UV-vis spectroscopy (low cost and fast measurements) with the mathematical deconvolution approach to determine the pigments' concentrations giving rise to a fast, cheap and useful tool for extra virgin olive oil characterization and quality assessment.…”

“…This spectroscopic approach has been already tested on extra-virgin olive oil samples produced in several Mediterranean countries (Spain, Greece, Italy and Tunisia), from different cultivars (such as Leccino, Moraiolo, Pendolino, Frantoio, Chemlali, Poniente de Granada, Arbequina, Koroneijki, Cornicabra and so on), and it was validated by comparing it with the other analytical methods [45,46], confirming its validity, goodness, and high reproducibility. Other studies mainly focused on monocultivar EVOOs produced in Tuscany (Italy) have shown the ability of this near UV-vis spectroscopic method to assess the high quality of EVOOs [47][48][49][50]. However, the main limitation of the method proposed by Domenici et al [40] is related to the not satisfactory reproduction of near UV-vis spectra of fresh extra-virgin olive oils.…”

Geographical Origin Assessment of Extra Virgin Olive Oil via NMR and MS Combined with Chemometrics as Analytical Approaches

“…These included PDO EVOOs from Sicily (Italy), and the approach used allowed researchers to identify and quantify the main metabolites possibly related to the geographical origin. Vicario et al, 2020 [ 96 ], characterized EVOO samples from a specific Italian area (Tuscany) combining 1 H and 13 C NMR with near UV-Vis absorption spectroscopy. The identified and quantified different chemical components, related to EVOOs’ nutritional and quality properties, were correlated with specific features of the cultivation area.…”

Analysis of Extra Virgin Olive Oils from Two Italian Regions by Means of Proton Nuclear Magnetic Resonance Relaxation and Relaxometry Measurements

“…In this way, it is possible to have a lot of information on the saponifiable fraction of olive oils. On the contrary, most of the numerous minor compounds of the unsaponifiable fraction cannot be easily quantified by 1 H NMR, except in specific cases. − Recent studies have been published, in which NMR has been used for the prediction of the olive oil geographical origin using NMR combined with multivariate statistical methods and to discriminate olive oils obtained from olives produced in different pedoclimatic conditions in combination with other spectroscopic techniques …”