Determination of dimethylamine in barley malt Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/0v838359n

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  • Dimethylamine (DMA), in addition to the alkaloids hordenine and gramine, has been suggested as a potential precursor of nitrosodimethylamine (NDMA) in malt. Analytical procedures were adopted and applied to extract and quantify DMA from malt, green malt, malt roots and raw barley. Ground malt was extracted at room temperature with 0.1 N HC1, and the extract was derivatized with 1% pentafluorobenzoyl chloride in benzene. After purification, the derivatized DMA was quantitated by gas chromatography with a thermionic N-specific detector. The method yielded a 96.3 per cent recovery for DMA, and exhibited a linear relationship between DMA concentration and GC peak height within a given range. The identity of the DMA derivative was confirmed by mass spectrometry. Commercial barley samples of 4 and 5-day germination of Klages variety were analyzed. The mean value for the 4-day germination Klages was 4.9, and for the 5-day, 11.7 μg/gm. The DMA level of 5-day germination Klages were significantly higher than the 4-day (P < 0.05). Levels of DMA in samples at each stage of the malting process were determined. DMA was found with a mean and range of 0.9 (0.6- 1.0); 0.6 (0.5-0.6); 11.6 (8.2-17.7); 513 (396-762); 5.9 (4.8-6.6); and 607 μg/gm (.571-637 μg/gm) on a dry weight basis for, respectively, raw barley, steeped barley, green malt, green malt roots, kilned malt and kilned malt roots. It was found that roots contained the highest levels of DMA. These results indicate that DMA is biosynthetically formed during germination. The nitrosation of 5 varieties of green and kilned malts (Winter, Morex, Klages, Piroline and Steptoe) was carried out to determine the significance of DMA as a precursor for NDMA. The amount of NDMA from DMA was compared to the amounts of NDMA from hordenine and gramine for each sample. In every sample the amount of NDMA from DMA was larger than the combined amount of NDMA from hordenine and gramine. The results strongly suggest that DMA is the primary precursor of NDMA in malt.
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