“As scientists, we were frustrated with the fact that we had so little objective data to rely on,” Professor Verstrepen explains his motivation. “Existing beer books offer the opinion of an expert who has tasted the beers, describes and rates them, but this approach is not always accurate and it also doesn’t tell you a lot. Hence the idea to map our amazing Belgian beers in an objective way.”
The aroma of beers is determined by hundreds of volatile substances. The Leuven-based lab is able to identify these substances using its state-of-the-art equipment for gas chromatography. “We take a sample of the volatile components that float above the beer,” Verstrepen explains. “We then inject these into a column, a long tube in which all compounds are separated from each other, so that we can identify and measure each of them separately. Professor Tom Wenseleers from the KU Leuven Department of Biology has been extremely helpful in writing the software to process the large amount of data collected with this test.”
For the taste analyses, Verstrepen and Roncoroni put together a tasting panel. “The selection was very strict. We started with thirty candidates, but half of them didn’t make the final cut. The remaining members of the panel were thoroughly trained and did blind tastings, in black glasses – all according to the rules. Of course, a tasting is always somewhat subjective, but working with a large and competent panel does yield consistent numerical data.”
On the basis of the collected data, the researchers were able to compose a map of Belgian beers. Kevin Verstrepen: “The position on the map has a meaning. The bottom right of the map shows the most bitter-tasting beers, for instance. Say you like Duvel and you would like to try something a bit more bitter, then it’s easy to see which beer you should try best. All you have to do is move a bit further along the bitterness axis.”
By analysing the components and flavours, Professor Verstrepen and his team revealed the complete aroma structures of the beers. The most surprising results? “You often hear that there’s supposedly no difference between Westvleteren and St. Bernardus Abt 12, but we were able to scientifically prove that this is not entirely true, although they are very similar. Sometimes, beers turned out to be something different than what they claim to be. For example, we had a look at the American Trappist beer Spencer and found that it differs from what we consider a Trappist beer.”
Most beer books offer the opinion of an expert who has tasted the beers, describes and rates them, but this approach is not always accurate and it also doesn’t tell you a lot.
“The map also shows which beers are somewhat isolated, these are the truly special beers. The very fruity and sweet Lindemans Pêcheressse is such an odd one out. Orval is also unique, a Trappist beer with very specific aromas.”
Can Kevin Verstrepen and his colleagues still enjoy a beer without analysing it? He laughs. “We’ve noticed that when we go to the pub with our colleagues from the lab the first thing we do is dip our noses into the glass and comment on what we can smell. And we can immediately taste it if the beer tap in the pub is not well maintained. That’s the downside of the training: you become a bit of a snob. Simply drinking a beer is no longer possible. My favourite beer? It depends on the circumstances. I can really enjoy a lager after mowing the lawn, but in the winter or after a good dinner I’ll sooner go for a dark beer.”