Hop to it: Researchers pinpoint why Belgian beers don't keep

By Daniel Boffey in Brussels

It will be music to the ears of Belgian beer enthusiasts: drink up.

Scientists studying how well the fashionable hoppy-tasting beers of today keep in the cupboard have highlighted the particular propensity for them to lose their flavour over time.

According to a paper produced by the Catholic University of Louvain, the humulones and cis-humulinones compounds vital to their hoppy taste degrade dramatically within two years of storage.

The result is a decrease of between 18% and 43% in what the scientists describe as “the calculated bitterness intensity of dry-hopped Belgian beers”.

The finding will have particular resonance for some in this period of stockpiling. In the days that immediately followed the coronavirus lockdown in the UK, the website of the retailer Majestic Wine crashed amid fears of a shortage of alcohol.

The academics from the Belgian city of Louvain behind the study, Ferreira Silva Guimarães, Antonio Carlos and Sonia Collin, examined the changes in the “bitterness units” in 21 Belgian dry-hopped beers.

While it has long been known that the flavour of beer changes over time, the impact of age on highly hopped and especially dry hopped beers has not been examined. In recent years, sales have been on the rise for beers made with strongly flavoured hops derived from the Humulus lupulus plant, or with whole hops added in the fermentation process.

The scientists report that humulones, cis-humulinones and hulupones are key to the “sensory and measured bitterness of these beers”.

After two years at 20C in the dark, they observed an average decrease of 91% of humulones and 73% of cis-humulinones.

“Alcohol content, extracts, and [acidicity] remained relatively stable through ageing, bitterness units (BU) suffered a major decrease,” the scientists report.

Belgium is Europe’s biggest exporter of beer, according to the latest statistics produced by the Brewers of Europe federation, with exports of 15.8m hectolitres; followed by Germany, the Netherlands and the UK. Germany consumed the most beer in 2018, followed by the UK, Spain and Poland.

A number of Belgian brewers and distilleries, including Stokerij Rubbens, De Moor and Filliers, have switched to the production of disinfecting hand gel in recent weeks.