N-nitrosamines in 21th Century

Significance of the topic

Carcinogenic N-nitrosamines have been a major concern in the food and beverage industry since their discovery in beer and malt in the 1970s. Their strong mutagenic and carcinogenic properties require sensitive monitoring and control, especially as modern brewing and malting processes seek to minimize their formation without compromising product quality.

Objectives and Study Overview

This article reviews historical developments in the analysis of N-nitrosamines over the last 15 years, focusing on advances in analytical methods and the current status of volatile and non-volatile N-nitrosamine occurrence in malt and beer. It also examines data from 2001–2015 on N-nitrosodimethylamine (NDMA) levels in commercial malt and beer samples.

Methodology and Instrumentation

Common approaches for volatile N-nitrosamines include gas chromatography coupled with chemiluminescence (GC-TEA) or mass spectrometric detection (GC-MS). Non-volatile compounds are quantified as Apparent Total N-nitroso Compounds (ATNC) via chemical denitrosation and TEA detection. Recent sample preparation techniques involve solid-phase extraction, headspace SPME, supercritical fluid extraction, microwave or ultrasonic extraction, and liquid chromatography–tandem mass spectrometry (LC-MS/MS) for simultaneous determination of both volatile and non-volatile nitrosamines.

Instrumental Setup

• GC-TEA for selective detection of volatile nitrosamines
• GC-MS and LC-MS/MS (APCI/ESI) for target and non-target screening
• Headspace SPME, SPE and novel extraction devices for rapid sample preparation
• High-resolution mass spectrometry (Orbitrap) for trace-level quantification

Main Results and Discussion

Analysis of 4 115 malt samples and 1 280 beer samples (2001–2015) showed mean NDMA levels in malt of ~0.8 μg/kg and in beer below the method LOQ (0.2 μg/kg), with sporadic exceedances of recommended limits (2.5 μg/kg in malt; 0.5 μg/kg in beer). The percentage of malt samples above 2.5 μg/kg declined to around 6 % in recent years (Pearson’s r = –0.81). Occasional high values were linked to microbial contamination or process deviations. Other volatile nitrosamines appeared only occasionally.

Benefits and Practical Applications

• Improved quality control in malt and beer production
• Enhanced food safety monitoring according to international guidelines
• Risk assessment of human exposure through diet and beverages
• Optimization of malting and kilning processes to minimize nitrosamine formation

Future Trends and Opportunities

There is a clear need for novel analytical protocols to identify and quantify unknown non-volatile nitrosamines contributing to ATNC. Advances may include targeted high-resolution MS workflows, QSAR modeling of carcinogenicity, and exploration of C-nitroso compounds in beer matrices. Understanding transnitrosation pathways in vivo will refine risk assessments for regular beer consumers.

Conclusion

Since the 1970s, technological improvements have drastically reduced volatile N-nitrosamines in malt and beer. However, non-volatile nitrosamines remain largely uncharacterized and may pose hidden risks. Ongoing research into advanced analytical techniques and the chemistry of nitrosation will support comprehensive monitoring and ensure brewing safety.

References

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