Fluorescence Spectroscopy Identifies Phenolic Content Of Healthy Olive Oils

What’s a salad without a smooth pour of olive oil? After all, users know it contains “good” fat and has plenty of health benefits.

Olive oil includes phenolic compounds, which scientists believe, can contribute to a lower rate of coronary heart disease, and prostate and colon cancers. Phenolic compounds also impact sensory attributes and the oxidative stability of olive oils.

Researchers can use fluorescence spectroscopy, near-infrared spectroscopy and mid-infrared spectroscopy to measure those phenolic compounds and determine the makeup of olive oil. But fluorescence spectroscopy, they found, can do it faster.

Phenolic compounds from medicinal herbs and dietary plants include phenolic acids and other components. Various bioactivities of phenolic compounds are responsible for their chemopreventive properties, like antioxidant, anticarcinogenic, or antimutagenic and anti-inflammatory effects.

These activities also contribute to the phenolic compounds’ inducing the natural death of a cell by arresting cell cycle, regulating carcinogen metabolism and ontogenesis expression, inhibiting DNA binding and cell adhesion, migration, proliferation or differentiation, and blocking signaling pathways.

The popular Mediterranean diet, which is largely vegetarian, includes consuming large amounts of olive oil.

Olive oil is a source of at least 30 phenolic compounds. These compounds are strong antioxidants and radical scavengers, both healthy substances.

Antioxidants are compounds found in food that stop or delay damage to the cells. Radical scavengers help protect cells from the damage caused by free radicals. “Free radicals” refers to compounds that are highly reactive. It can bind to cells and is most often connected to cell damage that leads to cancer development.

But refined oils lack the antioxidants and anti-inflammatories that gives unrefined extra-virgin olive oil its phenolic benefits. Regular olive oil is refined and stripped of important nutrients and antioxidants. 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.

Researchers have found that olive oils have unique fluorescent fingerprints. In fresh, extra-virgin olive oil, fluorescence emissions originate from phenols, tocopherols, and chlorophylls. New fluorescence appears from oxidation products during oil deterioration and the accompanying loss of health-boosting compounds.

Therefore, researchers can use fluorescence spectroscopy in olive oil analysis for screening fluorescent components during storage. That allows you to monitor extra-virgin olive oil deterioration. Moreover, fluorescence spectroscopy can be used to quantify the adulteration of extra-virgin olive oils with refined and deodorized oil.

Spectra of food can provide unique sample fingerprints to assess the quality of food. Front-face fluorescence measurements, coupled with chemometrics were used in one study to develop models to discriminate between virgin olive oils with low and high total phenolic contents, using fluorescence spectra, and to determine total phenolic content concentration. Chemometrics is a collection of mathematical and statistical methods to improve the understanding of chemical information.

The study, using fluorescence spectroscopy, showed that it can provide fast screening for total phenolic content of olive oils.

Researchers recorded fluorescence spectra for the study using a HORIBA Fluorolog® 3-11 spectrofluorometer, a sensitive and versatile modular spectrofluorometer with TCSPC lifetimes and interchangeable accessories. The basic configuration of the instrument included single-grating monochromators in excitation and emission positions, and a red-sensitive photomultiplier.  Scientists used the Fluorolog to measure excitation-emission matrices, as well as for recording EEMs and synchronous and total synchronous spectra of food samples.

That team recently received 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. The researchers expect to use the Aqualog for fast recording of EEMs of food.