Abstract
In recent years, a large number of biological properties and an important role in the organoleptic characteristics of olive oil have been attributed to phenolic secoiridoids, such as oleacein, oleocanthal, oleuropein aglycone and ligstroside aglycone. Consequently, quantifying them is of great interest for the olive oil sector. Currently, there is no consensus in which analytical method must be use to accurately determine these compounds in olive oil, mainly owing to the lack of reference standards for calibration. In this work, analytical standards of phenolic secoiridoids have been used to develop a quantitative and rapid analytical method by UHPLC-MS/MS, in which sample extraction is not carried out. Simple dilutions of the sample with dry tetrahydrofuran and dry acetonitrile were performed before analysing them. It is worth noting that under these conditions the generation of artefacts such as acetals and hemiacetals of the aldehydic forms is highly reduced. The detection and quantification was performed with a Xevo TQS tandem quadrupole mass spectrometer. The method was validated at four concentration levels and finally applied to six samples of extra virgin olive oil.
Highlights
In recent years, a large number of biological properties and an important role in the organoleptic characteristics of olive oil have been attributed to phenolic secoiridoids, such as oleacein, oleocanthal, oleuropein aglycone and ligstroside aglycone
Monoaldehydic forms are favoured in the olive oil, in specific varieties and depending on the oil production parameters, dialdehydic forms can be major phenolics[10]
The main difference with respect to other chromatographic methods collected in the literature is the joint use of analytical standards and the direct determination of secoiridoids
Summary
A large number of biological properties and an important role in the organoleptic characteristics of olive oil have been attributed to phenolic secoiridoids, such as oleacein, oleocanthal, oleuropein aglycone and ligstroside aglycone. In addition to the hydroxytyrosol (3,4-DHPEA, 1) derivatives, at least the tyrosol (p-HPEA, 2) derivatives should be considered in the calculation of “olive oil polyphenols” content to support the health claim of EU5 All these derivatives are classified as secoiridoids (or phenolic secoiridoids) which represent the most abundant subclass of phenolic compounds in olive oil. An analytical method to determine oleuropein and ligstroside aglycone isomers, oleacein and oleocanthal can allow to verify the health claim of EU in the labelling of an olive oil and be of assistance, together with the sensory tasting panel, to classify olive oil. A study has shown the “variability of judgment in the organoleptic evaluation” in common commercial EVOOs15
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