What is the test for phenols

An inexpensive and easy test to check health claims for olive oil

The polyphenols contained in olive oil have been shown to protect blood lipids from oxidative stress - a physiological burden on the body that can lead to DNA mutations and, as a result, to cancer, heart and blood diseases, diabetes and neurodegenerative diseases. According to the European regulation, this benefit only comes into play from a daily consumption of 20 g of olive oil and may only be advertised if this daily dose contains a total of at least 5 mg of hydroxytyrosol and hydroxytyrosol derivatives. However, verifying that this requirement has been met is not as easy as one might assume. "There are complex chromatographic processes, such as high-performance liquid chromatography (HPLC) in combination with a detector for ultraviolet and visible light or a mass spectrometer, with which the phenol content of virgin olive oils can be determined," explains Giuseppe Di Lecce from the University of Bologna. "However, these systems can only be used with very expensive analysis tools and by qualified technicians." Together with a team of researchers from the Universities of Bologna and Vigo, Di Lecce developed a simple analysis method with which the phenol content of extra virgin olive oils can be determined. The results of their preparatory study, funded under the OLEUM project, are encouraging. "The results show that the Folin-Ciocalteu reagent, which enables simple and inexpensive colorimetric testing, can also be used to successfully check compliance with the EU regulation on health claims with regard to polyphenols," emphasizes Di Lecce. This so-called FC method is a common colorimetric test that can be carried out in any laboratory with statistical software. If the hydroxytyrosol level is evaluated, the results are comparable with those obtained after hydrolysis with the HPLC-UV method using hydroxytyrosol and tyrosol. Next, the team will now analyze numerous samples in order to be able to draw final conclusions. However, these initial results suggest that small laboratories and manufacturing companies will soon benefit from faster and innovative instrumental approaches to assessing the quality and authenticity of olive oils. The EUR 5 million OLEUM project was funded under Horizon 2020. The overriding goal was to protect the quality and authenticity of olive oils worldwide. Further breakthroughs are expected by the project's completion in 2020, including the development of a reliable way of identifying the phenolic compounds in virgin olive oils that is in line with EU regulation. More information: CORDIS project page