Scientists believe phenolic compounds, like those found in olive oil, can contribute to a lower rate of coronary heart disease and prostate and colon cancers.
Natural phenolic compounds play an important role in cancer prevention and treatment, according to the National Institutes of Health.
Phenolic compounds from medicinal herbs and dietary plants include phenolic acids, flavonoids, tannins, stilbenes, curcuminoids, coumarins, lignans, quinones, and others. Various bioactivities of phenolic compounds are responsible for their chemopreventive properties, like antioxidant, anticarcinogenic, or antimutagenic and anti-inflammatory effects, and also contribute to their inducing apoptosis by arresting cell cycle, regulating carcinogen metabolism and ontogenesis expression, inhibiting DNA binding and cell adhesion, migration, proliferation or differentiation, and blocking signaling pathways.
Olive oil is a source of at least 30 phenolic compounds. The popular Mediterranean diet, which is largely vegetarian in nature, includes the consumption of large amounts of olive oil.
The phenolic compounds present in olive oil are strong antioxidants and radical scavengers, both healthy substances.
Antioxidants are compounds found in food that stop or delay damage to the cells. Free radicals is a general term used for compounds that are highly reactive. That means that these substances can attach and bind to, and ultimately damage normal cells in the body. Free radicals are most often implicated in cell damage that leads to cancer development, according to the National Center for Biotechnology Information, a part of the National Institutes of Health.
Radical scavengers are substances, such as antioxidants, that help protect cells from the damage caused by free radicals. Refined oils lack the antioxidants and anti-inflammatories that gives unrefined extra-virgin olive oil its benefits.
Regular olive oil is refined and stripped of important nutrients and antioxidants, according to the Olive Wellness Institute. In contrast, the natural extraction process used to produce extra-virgin olive oil ensures it retains all the nutrients and antioxidants from the olive fruit.
Fluorescence spectroscopy has the potential to directly screen olive oils for total phenolic content.
Ewa Sikorska is an associate professor at Poznań University of Economics and Business in Poznań, Poland. She serves on the Faculty of Commodity Science, Department of Technology and Instrumental Analysis. Sikorska has a Ph.D. in chemistry and D.Sc. (doctorate in science).
Among other things, Sikorska works at characterizing the compounds found in olive oils.
“Olive oils have unique fluorescent fingerprints,” she said. “In fresh, extra-virgin olive oil, emissions originate from phenols, tocopherols and chlorophylls. During oil deterioration, new fluorescence appears from oxidation products.”
She and her colleagues studied this phenomenon. The research team consisted of Professor Francesco Caponio, Ph.D. and Professor Antonella Pasqualone, Ph.D., from the Department of Soil, Plant and Food Sciences, Food Science, and Technology Unit, at the University of Bari in Italy; and Professor Igor Khmelinskii, Ph.D., from Universidade do Algarve, in Faro, Portugal.
The study revealed that researchers might use fluorescence in olive oil analysis for screening fluorescent components during storage, to monitor extra-virgin olive oil deterioration. Moreover, other studies showed that fluorescence, as well as other spectroscopic techniques including NIR (near infrared spectroscopy) and MIR (Mid-infrared spectroscopy) might be used to quantify the adulteration of extra-virgin olive oils with refined and deodorized oil.
The focus of her study was on the application of the direct front-face fluorescence measurements, coupled with chemometrics. This regime was used for developing multivariate models to discriminate between the virgin olive oils with low and high total phenolic content (TPC) and the determination of TPC concentration.
Ewa Sikorska, Ph.D.
Her goal was to replace a wet chemistry model for measuring these compounds with a “green,” chemical additive-free spectroscopic procedure.“The phenolic compounds are important components of olive oils, as they affect health benefits, sensory attributes and oxidative stability of olive oils,” she said.
Sikorska and her associates used two different approaches in their study. First, they developed classification models to discriminate between samples with low and high TPC content using fluorescence spectra. Next, they developed calibration models using the multivariate regression analysis to establish the quantitative relationship between TPC and fluorescence spectra of olive oil samples.
The study involved, among other things, the recording and analysis of excitation-emission matrices (EEMs) of the oils.
Spectra of food can provide unique sample fingerprints. The application of chemometric methods enables researchers to use this fingerprints to assess quality of food. Different spectroscopic techniques provide complementary information about food.
The results show the potential of fluorescence spectroscopy for direct, or at least semi-quantitative screening of virgin olive oils for TPC.
“The result may contribute to the development of routine fast screening methods for TPC assessment, which may be an alternative to conventional assays,” Sikorska said. “Such method would be much cheaper and faster, and fulfils the requirements for green analytical chemistry.”
The researchers recorded the fluorescence spectra using a HORIBA Fluorolog® 3-11 spectrofluorometer. The basic configuration of the instrument includes single-grating monochromators in excitation and emission positions, and a red-sensitive photomultiplier.
“We used this instrument for measurement excitation-emission matrices in this study, as well as for recording EEMs and synchronous and total synchronous spectra of food samples in many other studies,” she said. “Particularly useful for this application is front face geometry, which enables direct study of opaque foodstuff.”
Sikorska’s team recently secured a HORIBA Aqualog® spectrofluorometer. The Aqualog acquires Absorbance, Transmittance and the fluorescence Excitation-Emission Matrices (A-TEEM) simultaneously. It acquires EEMs up to 100 times faster than with conventional scanning fluorescence instruments.
“We intend to use this instrument for fast recording of EEMs of food,” she said.
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