Beer foam stability is controlled by a protein present in the liquid, with higher concentrations in triple‑fermented beers. Individual bubbles are separated by thin liquid films that thin over time because of pressure from surrounding bubbles; when films become thin enough bubbles burst and foam collapses. Fermentation frequency influences foam longevity because repeated fermentations produce more of the stabilizing protein while converting sugars to CO2 and alcohol. Triple‑fermented Belgian styles tend to retain foam far longer than typical ales and lagers. A lasting foamy head boosts aroma, enhances mouthfeel, and improves visual appeal. Microscopic imaging compared multiple commercial beers, including Belgian tripels and common lagers.
Being given a pint without a nice thick foamy head is a common cause of frustration for pub-goers. But according to a new study, it might not be due to bar staff botching the pour. Scientists in Switzerland and the Netherlands have found that the stability of beer foam is due to a protein present in the liquid. And this protein tends to be more abundant in 'triple-fermented' beers, which are especially popular in Belgium.
According to the team at ETH Zurich and Eindhoven University of Technology, individual beer bubbles are separated by thin films of liquid, which gradually become thinner after the beer has been poured, due to pressure from surrounding bubbles. When the liquid films get thin enough, the bubbles burst and the foam collapses. But the rate at which this occurs is closely related to the fermentation process, which converts sugars to CO2 and alcohol.
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