B-400.15.155 [2020-10] Nitrosamines in Wort and Beer
Biogenic amines arise as bacterial metabolites through decarboxylation of amino acids, amination of amino acids, aldehydes and ketones as well as through the degradation of nitrogenous substances. Elevated levels in foods are an indicator for inferior quality and can even make foods unpalatable. In higher doses, they can trigger headaches and migraines.
Ordinarily, only very small amounts of amines are present in beer. Elevated levels of amines are the result of contamination with wort bacteria (Enterobacteriaceae) prior to yeast pitching.
Compounds belonging to the nitrosamine group exhibit very strong carcinogenic properties. To date, only nitrosodimethylamine (NDMA) has been detected in beer.
Application/Purpose
Determination of the nitrosamine content in wort and beer.
Scope of Application
This method is suitable for wort and beer.
Principle
NDMA present in wort and beer is extracted on Extralut® or a comparable material using dichloromethane, followed by concentration of the eluate. The determination is performed with a gas chromatograph with a specific TEA detector (thermal energy analyzer); nitrosodipropylamine (NDPA) or nitrosodiisopropylamine (NDiPA) serves as an internal standard (ISTD). This detector analyzes nitrosamine according to the following procedure: After exiting the GC column, the separated substances are heated to approximately 500 °C in a pyrolyzer. At this temperature, the (N-NO) bond of the nitrosamine is broken, thus forming an NO radical (NO·):
The NO radicals then flow into a reaction chamber along with ozone, which is created by a special generator designed for this purpose. The following chemical reactions take place in the chamber:
|
NO· + O3 |
→ |
NO2· + O2 |
| NO2· |
→ |
NO2 + h•ν |
These NO radicals react with ozone, forming nitrogen dioxide in an excited state (NO·2). The NO·2 molecules decompose spontaneously to form nitrogen dioxide in its common form (NO2), emitting radiation (h•ν) at a wavelength of approx. 600 nm.