Evaluation of total phenolic content in virgin olive oil using fluorescence excitation–emission spectroscopy coupled with chemometrics

Abstract

BACKGROUND: Determination of the total phenolic content (TPC) in olive oils is of great interest, as phenolic compounds affect the health benefits, sensory attributes and oxidative stability of olive oils. The aim of this study was to explore the feasibility of direct front-face fluorescence measurements coupled with chemometrics for developing multivatiate models for discrimination between virgin olive oils with low and high TPC and determination of TPC concentration. (R 2 = 0.951, RPD = 4.0). RESULTS: Parallel factor analysis and principal component analysis of fluorescence excitation-emission matrices (EEMs) of virgin olive oils revealed different fluorescent properties for samples with low and high TPC. A perfect discrimination of oils with low and high TPC was achieved using partial least squares (PLS) discriminant analysis. The best regression model for the prediction of TPC was based on the PLS analysis of the unfolded entire EEMs CONCLUSIONS:The results show the potential of fluorescence spectroscopy for direct screening of virgin olive oils for TPC. This may contribute to the development of fast screening methods for TPC assessment, providing an alternative to conventional assays. The procedure is environmentally friendly and fulfils the requirements for green analytical chemistry.

Monitoring Virgin Olive Oil Shelf-Life by Fluorescence Spectroscopy and Sensory Characteristics: A Multidimensional Study Carried Out under Simulated Market Conditions

“…The second group of bands was identified at 250-350 nm of emission wavelengths, the excitation/emission maximum (λ ex /λ em ) being found at 293/322 nm in all the oils. This band corresponded simultaneously to tocopherols and phenols, as it was extensively reported in previous works [19,21,24,26]. Figure 1b shows the changes of the contour maps of the EEMs of the VOOs during the storage under moderate conditions.…”

“…The individual contribution of tocopherols and phenols has been studied by synchronous fluorescence spectroscopy [4,24] and by using a vitamin E standard and a VOO phenol extract [48]. Some works used this band to develop models to estimate the concentration of tocopherols in vegetables oils [24,49] or even to classify oils according to their concentration of phenols [26].…”

“…However, it was difficult to assign each component to one specific derivative. Secondly, the emission profiles of component 2 (λ ex /λ em 293/322 nm) and component 5 (λ ex /λ em 280/314 nm) were both assigned to tocopherols and phenols [21,26,29]. Previous research works dealing with the study of the individual contribution of tocopherols and phenols by means of synchronous fluorescence spectroscopy reported that tocopherols were related with higher excitation/emission wavelengths compared with phenols [21].…”

“…Several authors have proposed using fluorescence spectroscopy to characterize VOO [22][23][24][25][26]. Other authors have applied this technique to detect frauds such as blends of olive oils with other vegetable oils [27,28].…”

The Potential of Apulian Olive Biodiversity: The Case of Oliva Rossa Virgin Olive Oil

“…Finally, the methanolic phase was filtered (0.45 µm, VWR International, Center Valley, PA, USA) into an amber glass vial. The phenolic extracts were used for the determination of the total phenolic content (TPC) by means of the Folin-Ciocalteu reagent, as previously reported [29,30]. In brief, 100 µL of extract was mixed with the same amount of Folin reactive (Sigma-Aldrich Co. LLC, St. Louis, MO, USA) and, after 4 min, 800 µL of Na 2 CO 3 (5% w/v in water) (Carlo Erba Reagents S.r.l., Cornaredo, Italy) were added.…”