‘Really rich physics going on’: the science behind a flat pint of lager

A perfect pint of beer may depend less on your bartender and more on molecular interactions happening between bubbles. Scientists have discovered that the stability of beer foam is directly linked to a barley protein called Liquid Transfer Protein 1.

"We now know the mechanism exactly and are able to help the brewery improve the foam of their beers," explains Prof Jan Vermant from ETH Zurich, who led what began as a "typical Friday afternoon project."

Using advanced imaging techniques, researchers observed how this protein behaves differently depending on fermentation methods. In single-fermented beers like lagers, the proteins form small spherical particles that create unstable foam.

With each additional fermentation, the protein structure changes dramatically. By the third fermentation, protein fragments develop water-repellent and water-loving ends that create a phenomenon called the Marangoni effect, stabilizing bubbles for up to 15 minutes.

The findings could help brewers adjust foam levels to preference, though Vermant acknowledges foam appreciation varies culturally. For some beer enthusiasts, this research might finally explain why some brews maintain that perfect frothy top while others fall flat.