The Impact of Hop Freshness on Kettle-Hopped Beers

Hops are an indispensable ingredient in beer, and the differences in their chemical composition impart the various tastes and aromas associated with different beers. However, during storage, hops undergo changes in their chemical composition. Here, the changes in aroma and bitterness of kettle-hopped beers were evaluated in an experiment conducted on three different hop varieties (Aurora, Celeia and Styrian Wolf) with five different hop storage index (HSI) values (0.3-0.7). Hops were added to boiling wort for 5, 45 and 90 min. Alpha-acids, iso-alpha-acids, humulinones, bitterness units and hop aroma compounds in the samples were chemically analysed. All samples also underwent sensorial analysis. The old hops were not problematic in terms of bitterness or early hopping time. However, later additions of old hops reduced the quality and intensity of the hop aroma. The limit value for use without negative consequences for kettle hopping was set at HSI 0.5 for Aurora and Celeia and HSI 0.6 for Styrian Wolf.

Automated summary

Hops are vital for beer and contribute to its distinctive tastes and aromas. However, their chemical composition changes during storage, affecting the aroma and bitterness of kettle-hopped beers. This study evaluated the effects of three hop varieties and five hop storage index values on aroma and bitterness. The findings showed that old hops did not compromise bitterness or early hopping time, but later additions of old hops reduced hop aroma quality and intensity. The recommended limit values for kettle hopping without negative consequences were determined for different hop varieties and storage indexes.