R-200.30.154 [2016-03] Nitrosamines in Malt
Application/Purpose
This method describes the determination of nitrosamines in malt.
Compounds belonging to the nitrosamine group exhibit very strong carcinogenic properties. To date, only nitrosodimethylamine has been detected in malt, wort and beer (only smoked malt and products produced with smoked malt contain substantial amounts of other nitrosamines). For this reason, detection of nitrosamines in malt, wort and beer is limited to nitrosodimethylamine (NDMA).
Scope of Application
Malt intended for use in beer brewing or elsewhere in the food industry
Principle
A (modified) Congress wort is produced from malt samples prior to analysis. NDMA present in the Congress wort is extracted using dichloromethane followed by concentration of the eluate. The determination is performed with a gas chromatograph using a packed Carbowax 20M column with a specific TEA detector (thermal energy analyzer); nitrosodipropylamine (NDPA) serves as an internal standard.
This detector analyzes nitrosamine according to the following procedure:
After exiting the GC column, the separated substances are heated to 500 °C in a pyrolyzer. At this temperature, the N-NO bond of the nitrosamine is broken, thus forming an NO radical (NO۰):
The gas mixture then flows through a special filter (CTRTM gas stream filter), which only allows the carrier gas and the NO radicals to pass. After exiting the filter, the NO radicals flow into a reaction chamber along with ozone, which is created by a special generator. The following chemical reactions take place in the chamber:
|
NO• + O3 |
→ |
NO2• |
|
NO2• |
→ |
NO2 + h•ν |
These NO radicals react with ozone, forming nitrogen dioxide in an excited state (NO2•). The NO2• molecules decompose spontaneously to form nitrogen dioxide in its common form (NO2), emitting radiation (h•ν) with a wavelength of approx. 600 nm.