/ WORT, BEER AND BEER-BASED BEVERAGES / Wort and Beer / Low Molecular Weight Nitrogenous Compounds

B-400.15.155 [2025-04] Nitrosamines in wort and beer - gas chromatography

The group of nitrosamines has been shown to have very strong carcinogenic properties. The carcinogenic effect is based on reactive metabolites of nitrosamines in the metabolism, which react with the genetic material DNA, thereby damaging it and triggering tumors.

Nitrosamines are formed in an acidic environment from secondary amines through the action of nitrosating agents. On the other hand, nitrosamines can also be formed endogenously by the body's own bacteria.

So far, only dimethylnitrosamine has been detected in malt, wort and beer (only smoked malt and products made from it still contain significant amounts of other nitrosamines). The detection of nitrosamines in malt, wort and beer is therefore limited to the detection of dimethylnitrosamine (NDMA).

In order to limit the intake of nitrosamines via beer for the consumer, technical guideline values for NDMA have been defined. These are 2.5 μg/kg for malt and 0.5 μg/kg for beer.

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Application/Purpose

Determination of the nitrosamine content in wort (plant wort) and beer.

Scope of Application

This method is suitable for wort (plant wort) and beer.

The method is not suitable for determining the NDMA content in malts from a congress wort or other laboratory wort.

Principle

The NDMA is extracted from the wort (plant wort) and beer on Extrelut®, Tox Elut® or comparable material using dichloromethane and the eluate is then concentrated. The determination is carried out by gas chromatography with the specific TEA detector ("Thermal Energy Analyzer"). Nitrosodipropylamine (NDPA) or nitrosodiisopropylamine (NDiPA) is used as the internal standard (ISTD). This detector detects nitrosamines according to the following scheme: After exiting the GC column, the separated substances first enter a pyrolysis oven, where they are heated to around 500 °C. The detector is used as an internal standard (ISTD). At this temperature, the (N-NO) bond of the nitrosamines breaks down, forming an NO radical (NO^-):

The gas mixture then passes through a special filter (CTR Gas Stream Filter), which only allows the carrier gas and NO radicals to pass through. The NO radicals and ozone produced by a special generator then flow into a reaction chamber, where the following reaction takes place:

NO· + O₃	→	NO₂· + O₂
NO₂·	→	NO₂+ h•ν

These NO radicals react with ozone to form nitrogen dioxide in an excited state (NO₂^-) and oxygen. The NO2- decomposes spontaneously into ordinary nitrogen dioxide (NO₂) by emitting radiant energy (h-ν) at a wavelength of around 600 nm.