Copper-based fungicides are highly relied upon in both conventional and organic hop production; however, copper (II) is known to destroy many components related to hop aroma quality. While this phenomenon has been examined to a limited degree in long-established hop yards in Europe and the Western U.S, it has not been investigated in the burgeoning hops industry of the Northeast U.S., where increased humidity, rainfall, and disease pressure pose a greater obstacle in the production of high-quality hops. Herein, we present the results of a field trial conducted at Penn State’s Research Hopyard, wherein we examined the influence of copper-based fungicide field application on hop aroma quality in Cascade hops. Copper fungicide applications consisted of a copper hydroxide-based fungicide in combination with a copper-free fungicide while control hops received only the copper-free fungicide. Analysis of α- and β-acids, as well as essential oil profiling, revealed no differences between fungicide treatments. Beers dry-hopped with copper-treated or control samples were evaluated for sensorial differences by beer consumers (n=92) using triangle tests designed to discern differences in aroma and taste. Participants were unable to differentiate between beers based on orthonasal aroma alone (p=0.10) but were able to distinguish between treatments upon consumption (p=0.02) indicating a difference in basic taste or retronasal olfactory perception. Perceived differences may be due to the hop-varietal thiol content of the beers. These thiols impart desirable aromas such as black currant or grapefruit but are labile to oxidation by copper (II). While this copper/thiol interaction has been characterized within food systems, considerably less attention has been paid to the connection between field treatments and finished food quality. Differences in hop-derived thiol concentrations, reported here, were analyzed in hops and beer samples to determine the potential effects of fungicide treatment on thiol content.

Effects of copper-based fungicides on Pennsylvania hop quality

2019 Fall National Meeting

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