With the increase of average temperatures, the quality of Žatec hops is becoming worse, according to a team of Czech and British scientists.
The researchers compared weather data and data about hop harvests and quality in records from 1891 to 2006, with a special focus on the last 50 years. They did not pick this plant just because it is a key ingredient in the production of the Czech national beverage.
“The Žatec Red is traditional aromatic hops, with a stable genetic base, that has been grown in the Žatec hop region for a long time. Its response to changing climate conditions is not distorted by the introduction of new varieties, as is the case with many field plants. This gives us a unique opportunity to study the impacts of climate change in practice,” says Martin Možný, head of research at the Czech Hydrometeorological Institute in Doksany.
Less bitter acidity
With the increasing average temperature, the period vegetation for hops begins earlier but also lasts for a shorter amount of time. This has meant smaller harvest. Most importantly, it means there is not enough time for the production of alpha acids in the hops – substances that give beer its unique bitter flavour.
“We saw an absolutely clear, statistically significant relationship between higher temperatures and a lower proportion of alpha acids in hops,” says Možný.
The biggest jump in temperatures took place in the last 25 years, and hops harvested in those years had the lowest level of “bitter” alpha acids. While in the 1950s and 1960s alpha acids made up 5% to 6% of each hop cone, the amount decreased gradually, and by the turn of the century it was at 3%.
Moving the plants from traditional areas
“This basically shows that if the warming continues, growing hops in the traditional areas will no longer be profitable,” says Možný.
It will be necessary to switch to some new breed of hops that is less affected by warmer temperatures. Another option can be to move traditional hop growing to new, colder areas – further north or to higher elevations.
“Records from the 16th century show a similar trend,” says Možný. ” Between 1517 and 1540, our part of the world experienced warmer temperatures and hop growing was successfully moved to more northern areas.”
