Carbonyl compounds and furan derivatives with toxic potential evaluated in the brewing stages of craft beer

Carbonyl compounds and furan derivatives may form adducts with DNA and cause oxidative stress to human cells, which establishes the carcinogenic potential of these compounds. The occurrence of these compounds may vary according to the processing characteristics of the beer. The objective of this study was, for the first time, to investigate the free forms of target carbonyl compounds [acetaldehyde, acrolein, ethyl carbamate (EC) and formaldehyde] and furan derivatives [furfural and furfuryl alcohol (FA)] during the brewing stages of ale and lager craft beers. Samples were evaluated using headspace-solid phase microextraction and gas chromatography with mass spectrometric detection in selected ion monitoring mode (HS-SPME-GC/MS-SIM). Acetaldehyde, acrolein, formaldehyde and furfuryl alcohol were found in all brewing stages of both beer types, while EC and furfural concentrations were below the LOD and LOQ of the method (0.1 and 0.01 µg L⁻¹, respectively). Boiling and fermentation of ale brewing seem to be important steps for the formation of acrolein and acetaldehyde, respectively, while boiling resulted in an increase of FA in both types of beer. Conversely, pasteurisation and maturation reduced the levels of these compounds in both types of beer. An increase in concentration of acrolein has not been verified in lager brew probably due to the difference in boiling time between these two types of beer (60 and 90 min for ale and lager, respectively).

羰基化合物与呋喃衍生物可与DNA形成加合物，并对人体细胞造成氧化应激，由此证实此类化合物具备致癌潜力。此类化合物的含量水平会随啤酒的加工工艺特性发生变化。本研究首次针对艾尔精酿啤酒与拉格精酿啤酒的各酿造阶段，对目标羰基化合物[乙醛（acetaldehyde）、丙烯醛（acrolein）、氨基甲酸乙酯（ethyl carbamate, EC）与甲醛（formaldehyde）]及呋喃衍生物[糠醛（furfural）、糠醇（furfuryl alcohol, FA）]的游离态含量展开调查。采用顶空固相微萃取-气相色谱-质谱联用选择离子监测模式（HS-SPME-GC/MS-SIM）对样品进行检测分析。乙醛、丙烯醛、甲醛与糠醇在两种啤酒的全部酿造阶段中均有检出；而氨基甲酸乙酯与糠醛的浓度则低于本方法的检出限（LOD，0.1 μg·L⁻¹）与定量限（LOQ，0.01 μg·L⁻¹）。艾尔啤酒酿造的煮沸与发酵工序，分别是丙烯醛与乙醛形成的关键步骤；而煮沸工序则会使两种啤酒中糠醇的含量上升。与之相反，巴氏杀菌与后熟工序则会降低两种啤酒中此类化合物的含量水平。拉格啤酒酿造过程中未检出丙烯醛浓度上升，这可能是因为两种啤酒的煮沸时长存在差异（艾尔啤酒煮沸时长为60分钟，拉格啤酒为90分钟）。