The fates of more than 300 pesticide residues were investigated in the course of beer brewing. Groundmalt artificially
contaminated with pesticides was brewed via steps such as mashing, boiling, and fermentation. Analytical samples were taken from
wort, spent grain, and beer produced at certain key points in the brewing process. The samples were extracted and purified with the
QuEChERS (Quick Easy Cheap Effective Rugged and Safe) method and were then analyzed by LC-MS/MS using a multiresidue
method. In the results, a majority of pesticides showed a reduction in the unhopped wort and were adsorbed onto the spent grain
after mashing. In addition, some pesticides diminished during the boiling and fermentation. This suggests that the reduction was
caused mainly by adsorption, pyrolysis, and hydrolysis. After the entire process of brewing, the risks of contaminating beer with
pesticides were reduced remarkably, and only a few pesticides remained without being removed or resolved.