Transfer of Nitrate and various Pesticides into Beer during Dry Hopping

We describe the transfer of nitrate and the pesticides azoxystrobin, dimethomorph, myclobutanil and quinoxyfen from contaminated hops to the beer during wort production and dry hopping. The experiments reported comprise of two experiment series conducted in a 20 hL pilot plant. First, the substance transfer was investigated by dry hopping different base beers with different amounts of various hop varieties and products. Secondly, a beer was brewed and dry hopped exclusively with a hop that had a high load of the four

aforementioned pesticides. The results are presented in terms of concentrations and processing factors. In a market survey, we also analyzed 14 commercial beer samples of different brands and types as well as different hop samples in regard to their nitrate concentrations which were in the range of 3.0 to 86.5 mg/L.

The six India Pale Ales of the commercial beer samples were also analyzed for a selected number of pesticides. None of the samples contained detectable amounts of those pesticides which were quantified after extraction using LC-MS/MS. Transfer of nitrate from hops to beer was nearly quantitative and scaled linearly with hop addition. Extraction of pesticides was strongly dependent on temperature and primarily limited by the water solubility of the compounds at the cold temperatures of maturation and fermentation. The dimensionless processing factors, defined as the residue level in the processed product in relation to the residue level in the raw product, had maximum values of 0.002.

BrewingScience - Monatsschrift für Brauwissenschaft, 67 (January/February 2014), pp. 1-9