Quantitation of benzene in flavourings and liquid foods containing added cherry-type flavour by a careful work-up procedure followed by a stable isotope dilution assay

The exposure of humans to the aromatic hydrocarbon benzene should be minimized due to its carcinogenicity. Previous studies have reported on the presence of benzene, in particular in foods with added cherry aroma compounds, in particular benzaldehyde. To allow a reliable quantitation of benzene, a stable isotope dilution assay using (²H₃)benzene as the internal standard was developed and solid phase microextraction (SPME) was used for volatile isolation followed by GC × GC–TOFMS analysis. Care was taken to avoid any exposure to light and to use materials during work-up, which were free of benzene contamination. The method, applied on 22 liquid foods with added flavour showed that benzene did not exceed a concentration of 1 µg/L in any sample (i.e. the limit established for drinking water). Furthermore, flavourings containing benzaldehyde and the corresponding raw material were analysed. The major source of benzene in flavourings turned out to be benzaldehyde itself. First insights into parameters supporting the formation pathway of benzene from benzaldehyde were obtained indicating that the presence of light and either acidic or alkaline conditions favoured benzene formation.