When it comes to the foam on your pint, Belgian beers are “a-head” of the game. A team of European researchers on a quest to determine what goes into making the perfect beer foam found triple-fermented Belgian beers came up top, possessing the most stable foam of the six drinks studied, while the foam single-fermented lager was the least.
The purpose of the study, published in the journal Physics of Fluids, was to better understand the formation of foam – and beer proved to be an excellent case study.
“The idea was to directly study what happens in the thin film that separates two neighboring bubbles,” Emmanouil Chatzigiannakis, an assistant professor at the Processing and Performance group of Eindhoven University of Technology in the Netherlands, said in a supporting statement. “And the first thing that comes to mind when thinking of bubbles and foams is beer.”
Belgian Beer Has the Most Stable Foam
Beer is big business. As one of the most popular alcoholic drinks globally, it contributed 555 billion dollars to the world economy in 2024, according to figures cited in the paper.
A key characteristic of beer is the foam that sits at the top of a pint. This comprises tiny bubbles of air coated in a thin film of liquid. When the film remains stable, the bubbles retain their shape and the foam holds. In contrast, the less stable the film, the quicker the bubbles pop, the foam dissolves and the head disappears.
To determine what exactly caused the foam to retain stability, the team studied six types of beer, including two Belgian tripels (Westmalle Tripel and Tripel Karmeliet), a Dubbel, a Singel, and two lagers. The team found that triple-fermented beers presented the most stable foam. The runner-up were beers fermented twice, while single fermented lager beers came in last place.
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What Increases (or Decreases) Foam Stability?
Surface viscosity is the primary factor affecting the stability of single-fermented lagers, which in turn is affected by the presence of proteins.
In short, the higher the number of proteins, the more stable the beer. But when a beer undergoes additional fermenting processes, the nature of protein LPT1 (lipid transfer protein 1) changes, which, in turn, increases the stability of the foam.
The researchers found that the foam in triple-fermented beers, such as the trappist beers brewed in European monasteries, retains its stability thanks to forces that occur due to differences in surface tension and maintain the structure of the bubbles. This boost to its stability means the head on a triple-fermented beer will outlast that of a lager.
What’s Next for Beer Research?
The researchers hope the findings will enable manufacturers to perfect their beer, but the findings could have many other benefits across a diverse range of industries that rely on foam – from treating varicose veins to improving the safety of electric vehicles.
“This is an inspiration for other types of materials design, where we can start thinking about the most material-efficient ways [of creating stable foams],” lead author Jan Vermant, professor of soft materials at ETH Zurich, Switzerland, said in a press release. Adding, “If we can’t use classical surfactants, can we mimic the 2D networks that double-fermented beers have?”
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