How do you get benzene from benzaldehyde

Benzene in cherry juice: how does it happen and how to avoid it

Flavors containing benzaldehyde can develop benzene when exposed to light.

In 2013, the Stiftung Warentest found benzene harmful to health in beverages with a cherry flavor. But how did the substance get into the drinks? Was benzaldehyde the source as an essential component of the cherry flavor? And if so, how can the problem be resolved? A new study by the Leibniz Institute for Food Systems Biology and the Technical University of Munich (TUM) now answers these questions.

According to the Federal Institute for Risk Assessment (BfR), benzene mainly enters our body through the air we breathe. Non-smokers ingest an average of around 200 micrograms of benzene per day. Smokers are about ten times more exposed. But food can also contain traces of this harmful substance and thus contribute to exposure.

When the Stiftung Warentest examined soft drinks in 2013, it came across small amounts of benzene. One drink contained just under 4.6 micrograms of benzene per liter. For comparison: In Germany, a liter of drinking water may only contain a maximum of 1 microgram of the substance. At the time, experts from Stiftung Warentest suspected that the odorous substance benzaldehyde was the cause of the benzene contamination observed.

"Since our research specializes in odorous substances, we followed this assumption in the interests of consumer protection and at the suggestion of the German Association of the Flavor Industry (DVAI)," says first author Stephanie Frank from the Leibniz Institute for Food Systems Biology at the Technical University of Munich .

To do this, the science team first established a reliable, highly sensitive detection method for benzene. It then carried out tests with various model solutions that contained benzene-free benzaldehyde. In addition, the team examined cherry juice produced under laboratory conditions, to which they also added the pure odorous substance.

Light is the decisive factor

“Our results confirm the assumption made by Stiftung Warentest and also explain how benzene is formed. An important prerequisite for a sustainable solution to the problem, ”reports food chemist Stephanie Frank.

As the study shows, the longer the odorous substance is exposed to light, the more benzene is produced from benzaldehyde. But the light intensity is also crucial. In contrast, the pH value, the oxygen content, the presence of metal ions or the temperature did not influence the benzene production in the model solutions.

To the surprise of the researchers, no benzene was formed in the cherry juice produced under laboratory conditions when exposed to light. Frank thinks it is likely that the dark red color of the drink acts like a light protection filter and thus prevents the formation of benzene. The benzene found in some commercially available juice spritzers is therefore presumably due to added cherry aroma that has already been contaminated with benzene.

"Aromas containing benzaldehyde should therefore be protected from light at all times - from production to sale, for example by storing them in tinted glasses," recommends Peter Schieberle, Professor of Food Chemistry at the Technical University of Munich.


S. Frank, A. Dunkel, P. Schieberle
Model studies on benzene formation from benzaldehyde
Eur Food Res Technol, Feb. 22, 2020 - DOI: 10.1007 / s00217-020-03455-6.

S. Frank, T. Hofmann, P. Schieberle
Quantitation of benzene in flavors and liquid foods containing added cherry-type flavor by a careful work-up procedure followed by a stable isotope dilution assay
Eur Food Res and Technol, 245 (8): 1605-1610 - DOI: 10.1007 / s00217-019-03267-3.

Additional Information:

The research work in the AiF 18813 N project was initiated by the Research Association of the Food Industry (FEI) through the Working Group of Industrial Research Associations "Otto von Guericke" eV (AiF) within the framework of the program to promote joint industrial research (IGF) by the Federal Ministry of Economics and energy based on a resolution of the German Bundestag.


Dr. Gisela Olias
Leibniz Institute for Food Systems Biology at the Technical University of Munich
Press and public relations
Lise-Meitner-Str. 34, 85354 Freising
Tel .: +49 8161 71-2980 - Email: [email protected]

Dr. Stephanie Frank
Leibniz Institute for Food Systems Biology at the Technical University of Munich
Section I / Working Group Sensory Systems Chemistry
Email: [email protected]

Prof. Dr. Peter Schieberle
Technical University of Munich
Faculty of Chemistry
Lichtenbergstrasse 4, 85748 Garching, Germany
Email: [email protected]

Source: TUM

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