Why The Foam On Belgian Beers Lasts So Long

Eddie Gonzales Jr. – MessageToEagle.com – Researchers at ETH Zurich have discovered the holy grail of brewing: the recipe for stable beer foam. But their findings aren’t just beneficial for breweries.

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Summertime is beer time – even though alcoholic beer consumption is declining in Switzerland. And for beer lovers, nothing beats a head of foam sitting atop the golden, sparkling beer.

But with many beers, this dream quickly shatters, and the foam collapses before you can even take the first sip. However, there are also beers where the head lasts a long time.

Researchers at ETH Zurich led by Jan Vermant, Professor of Soft Materials, have now discovered why this is the case. Their study has just been published in the journal Physics of Fluids. The Belgian and his colleagues have been working on it for seven years. It all began with a simple question to a Belgian brewer: “How do you control the brewing process?” – “By observing the foam,” was the answer.

Today, ETH scientists understand the mechanisms behind the perfect beer foam. And perhaps in the future, beer drinkers will be able to admire the foam in their glasses a little longer before quenching their thirst.

Triple beats double and single

In this study, the materials scientists showed that among the Belgian beers examined, “Tripel” beers have the most stable foam, followed by “Dubbel” beers. The least stable foam is found in “Singel” beers, which are less intensively fermented and have the lowest alcohol content.

The ETH researchers also examined two lagers from major Swiss breweries. The foam stability of these beers is comparable to that of Belgian ales, although the physics behind foam stability is different. Interestingly, one of the Swiss lagers tested did not perform as well in terms of foam stability. “Thanks to our new findings, we could definitely improve that,” says Jan Vermant.

Surface tension instead of viscosity

Until now, researchers assumed that the stability of beer foam depends primarily on protein-rich layers on the surface of the bubbles (see ETH  News ): The proteins originate from the barley malt and influence the surface viscosity, i.e. its flowability, as well as the surface tension.

But the new experiments show that the crucial mechanism is more complex and depends strongly on the type of beer.

In lager beers, the decisive factor is how elastic yet viscous the surface of the bubbles is (viscoelasticity). This is influenced by the proteins present in the beer and their denaturation: The more proteins present in the beer, the stiffer the film around the bubbles becomes and the more stable the foam becomes.

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Written by Eddie Gonzales  Jr. – MessageToEagle.com Staff Writer