Using Green Chemistry to Screen Olive Oils

14 Jun 2021

olive oil cooking

A quick, easy and environmentally–friendly method to measure healthy phenolic compounds in extra virgin olive oils could pave the way to food-grade analytical chemistry.

Research suggests that the regular consumption of phenolic compounds in extra virgin olive oil can help decrease the risk of cardiovascular disease. The European Food Safety Authority (EFSA) allows a health claim for labelling olive oils containing a minimum amount of hydroxytyrosol (OHTyr) and its derivatives, including tyrosol (Tyr).

Several analytical methods have been proposed to help assess the suitability of olive oils to support labelling with this health claim. As OHTyr and Tyr are present in extra virgin oils both in their free form, as well as esterified in several derivatives, quantifying each type is challenging. Performing acidic hydrolysis after extraction and before chromatographic analysis has previously been established as a satisfactory approach for measuring the total amount of both compounds, in both their free and linked forms.

But current protocols require the use of expensive equipment, toxic solvents and highly trained operators. Developing other faster, easier and more environmentally–friendly techniques could prove useful for on–site screening purposes and monitoring applications.

Non–Toxic Reagents Inspired By Nature

Natural deep eutectic solvents (NADES) are a mixture of two or more components obtained from molecules naturally present in living organisms as metabolites. These green solvents are being increasingly used for analytical purposes as alternatives to toxic reagents.

In a new study, published in Foods, researchers used a NADES composed of lactic acid, glucose and water to extract to determine the total amount of OHTyr and Tyr in extra virgin olive oils.1

The team performed a liquid/liquid extraction on 26 different olive oils, followed by UV–spectrophotometric analysis. They showed that the spectral features of the extracts were related to the content of total OHTyr and Tyr, determined by the acid hydrolysis method. The method had a limit of detection and quantification of 3.9 and 11.8 mg per kg respectively with satisfactory repeatability for screening purposes.

The researchers used ultrapure water generated by an ELGA PURELAB® laboratory water purification system, minimising the risk of introducing contaminants that may affect their results.

Food–Grade Analytical Chemistry

A new method using food–grade reagents was successfully set up as an on–site, environmentally and operator-friendly tool for screening extra virgin olive oils according to their total content of OHTyr and Tyr.

Requiring only non–toxic reagents and simple equipment, the NADES–UV method is both affordable and feasible to carry out in locations other than analytical laboratories – such as oil mills or bottling plants. It could therefore offer a suitable complement to existing, more complex techniques involving extraction, acid hydrolysis and chromatographical analysis.

A complete analytical platform comprising options for either on–site screening or accurate laboratory determination could offer greater protection for olive oil producers and consumers from products labelled with fraudulent health claims reaching the marketplace.

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Reference:

Paradiso VM, et al. Paving the Way to Food Grade Analytical Chemistry: Use of a Natural Deep Eutectic Solvent to Determine Total Hydroxytyrosol and Tyrosol in Extra Virgin Olive Oils. Foods 2021;10:677.

Dr Alison Halliday

After completing an undergraduate degree in Biochemistry & Genetics at Sheffield University, Alison was awarded a PhD in Human Molecular Genetics at the University of Newcastle. She carried out five years as a Senior Postdoctoral Research Fellow at UCL, investigating the genes involved in childhood obesity syndrome. Moving into science communications, she spent ten years at Cancer Research UK engaging the public about the charity’s work. She now specialises in writing about research across the life sciences, medicine and health.