This article examines the fate of four pesticides that can be present during the brewing of lager beer. For this purpose, malted barley was spiked at 2 mg/kg with pendimethalin and trifluralin (dinitroaniline herbicides) and fenitrothion and malathion (organophosphorus insecticides).
Analyses of pesticide residues were carried out by a gas chromatograph with an electron capture detector, and their identity was confirmed by gas chromatography–mass spectrometry. Cleanup was necessary for the malt and spent grain samples. Beginning with mashing and ending with the final
product 4 months later, various samples (spent grain, sweet wort, brewer wort, and beer) were taken to determine the concentration of the targeted residual pesticides during the various beer making phases. In all cases, the residual levels recorded in sweet wort sampled after the mashing phase
were below the respective maximum residue limits established by Spanish legislation for barley. Significant proportions of pesticide residues (17 to 40%) were retained on the spent grain. Applying the standard first-order kinetics equation (r > 0.91), the half-lives obtained for
the four compounds during the storage of the spent grain (3.5 months) varied from 138 days (fenitrothion) to 192 days (malathion and pendimethalin). Herbicide residues practically disappeared (<0.3%) after wort boiling, whereas the percentages of the remaining insecticides, fenitrothion
and malathion, ranged from 3.5 to 4.3%, respectively, at this time. No residues of dinitroaniline compounds were detected in young beer, whereas there was a significant reduction in fenitrothion (58%) and malathion (71%) residues during fermentation. Lagering and filtering processes also reduced
the content of the organophosphorus insecticides (33 to 37%). Finally, after the storage period (3 months), the content of fenitrothion was reduced by 75%, with malathion residues being below its detection limit.
Document Type: Research Article
Department of Agricultural Chemistry, Geology and Pedology, School of Chemistry, University of Murcia, Campus Universitario de Espinardo, E-30100 Murcia, Spain
Publication date: July 1, 2006
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