Impact of Copper Fungicide Use in Hops Production on the Total Metal Content and Stability of Wort and Dry-Hopped Beer
Transition metals, including copper, iron, and manganese, are known to catalyze the generation of reactive oxygen species (ROS) in beer and lead to reduced product stability. Metals in beer are generally derived from raw ingredients. The present study aims to evaluate the impact of brewing and dry-hopping using hops treated with copper-based fungicides (CuBFs) on the final transition metal content of model buffer solutions and pilot-scale systems of wort and beer. Copper levels in model wort and beer solutions were elevated (105.6% and 230.4% increase, respectively) when CuBF-treated hops were used. In laboratory-prepared wort, elevated copper concentrations were not observed when CuBF-treated hops were used for boiling. Dry hopping of beer using CuBF-treated hops led to significant increases in total copper content (ca. 75 µg/kg vs. ca. 40-50 µg/kg in the control-hopped beer) when yeast was absent from the treated beer, but not when yeast was present. It was observed that manganese levels were significantly elevated in all hopped beers (ca. 495-550 µg/kg vs. 90-125µg/kg in the unhopped control), regardless of hop treatment. 4-Mercapto-4-methylpentan-2-one, a hop varietal thiol, was spiked into treated beers and the rate of oxidative loss was monitored during aging. Rates of thiol loss in treated beer samples did not differ across CuBF treatments, but was significantly lower in unhopped controls in the absence of yeast (p < 0.0001) and correlated significantly with total manganese content of the beers (R2 = 0.4228, p = 0.0006). The rate of staling in hopped beers as measured by 1-hydroxethyl radical generation not differ among hop treatments, suggesting that excess copper content contributed from the hops does not negatively impact the oxidative stability of the beers.
|Work Title||Impact of Copper Fungicide Use in Hops Production on the Total Metal Content and Stability of Wort and Dry-Hopped Beer|
|License||All rights reserved|
|Deposited||June 04, 2020|
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