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N-nitrosodimethylamine precursors in malt
IARC Scientific Publications
|January 1, 1982
Summary
N-Nitrosodimethylamine (NDMA) forms in malt when nitrogen oxides (NOx) react with amines like hordenine during kilning. Malting techniques that prevent hordenine breakdown reduce NDMA formation, offering a way to control this contaminant.
Area of Science:
- Food Chemistry
- Agricultural Science
- Analytical Chemistry
Background:
- N-Nitrosodimethylamine (NDMA) is a potential contaminant formed during the malting process.
- The reaction involves nitrogen oxides (NOx) and amines present in germinated barley.
- Hordenine is identified as the primary precursor for NDMA formation.
Purpose of the Study:
- To elucidate the mechanism of NDMA formation during malt kilning.
- To identify the key precursors and intermediate compounds involved in NDMA synthesis.
- To investigate how malting techniques influence NDMA levels.
Main Methods:
- Analysis of amine precursors, specifically hordenine, in malt samples.
- Investigation of NDMA formation under varying kilning conditions.
- Separation and characterization of nitrosated intermediates using High-Performance Liquid Chromatography (HPLC).
- Controlled experiments involving NOx treatment of hordenine at different temperatures.
Main Results:
- Hordenine is abundantly present in unkilned malt, sufficient to account for observed NDMA levels.
- Malting techniques that reduce hordenine breakdown during kilning correlate with decreased NDMA formation.
- Nitrosated intermediates derived from hordenine were isolated and shown to yield NDMA upon further reaction with NOx.
- The formation and conversion of these intermediates align with NDMA patterns observed during kilning.
Conclusions:
- NDMA formation in malt is primarily driven by the reaction of NOx with hordenine.
- Controlling hordenine breakdown during malting is crucial for minimizing NDMA contamination.
- Understanding the role of nitrosated intermediates provides insights into optimizing malting processes to mitigate NDMA.
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