Rapid test detects quality and authenticity of olive oil

Extra virgin olive oil is one of the most popular foods in Europe, but inferior counterfeits are coming onto the market in increasing number. A research team led by Prof Dr Stephan Schwarzinger from the University of Bayreuth has now developed a highly effective rapid test to combat this food fraud, which can assess the quality, authenticity and origin of olive oils within just one hour.

Counterfeits of extra virgin olive oil have been a problem for many years. As explained by Prof Dr Schwarzinger, “Cheap alternative vegetable oils are dyed green and sold as olive oil, rancid oil is mixed with good oil or old oils are glossed over with special technologies and come back into circulation as extra virgin olive oil.”

Comprehensive tests of the quality and authenticity of olive oils could until now only be carried out using different test procedures applied one after the other, making them time-consuming and expensive. The new method, developed in cooperation with the University of Athens, analytical laboratory ALNuMed and partners from the olive oil industry, overcomes these obstacles with the help of nuclear magnetic resonance (NMR) spectroscopy, a technique that enables the rapid and simultaneous analysis of many parameters.

“Over several years, we collected and systematically analysed more than 1000 different samples of extra virgin olive oil,” said Prof Dr Schwarzinger, who heads the Working Group for Quality and Authenticity of Food and Materials at Bayreuth’s Northern Bavarian NMR Centre (NBNC). “The NMR measurement provided us with an individual profile for each sample that includes all properties relevant to quality and authenticity.”

The rapid test is based on the ability of NMR spectroscopy to detect ingredients that occur in very different amounts with high resolution and reproducibility. Practically, this means highly concentrated main ingredients — such as the fatty acids in olive oil — as well as very low concentrated substances can be detected. These include polyphenols, which act as antioxidants in the human body and have a positive effect on health. The test therefore indicates whether the oil examined is entitled, in principle, to bear a health claim according to the corresponding EU regulation.

Taste impressions are also tested, which are important for consumer acceptance. In addition, a comparison with existing olive oil profiles can be used to check how credible the declaration of origin of the respective producer or trader is. NMR spectroscopy can be used to check whether the examined olive oil sample comes from Greece, Italy or Spain, for example.

Prof Dr Schwarzinger recently presented the basics of the olive oil rapid test at the BioFach trade fair, which was this year held online due to the COVID-19 pandemic. “Our new test option met with broad interest,” he said.

“The olive oil experts were very impressed by how quickly and thoroughly the quality and authenticity of olive oils can be determined. It is already clear that this can significantly improve the transparency of olive oil supply chains and markets. We hope that our development will now be quickly implemented in contracting laboratories and brought to market.”

Image caption: Testing an olive oil sample at the North Bavarian NMR Centre on the campus of the University of Bayreuth. Image courtesy of ALNuMed.

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