Protein Power: The Science Behind Longer-Lasting Beer Foam

According to a study published in 2023, the stability of beer foam is determined by a specific protein present in the liquid. Researchers from Switzerland and the Netherlands have discovered that triple-fermented beers, particularly those popular in Belgium, contain higher levels of this protein, which helps the foam last longer compared to single-fermented ales and lagers.

The study examined six commercial beers, including Belgian tripels and dubbels, as well as Swiss lagers. The scientists found that the triple-fermented beers had the most stable foam, followed by double-fermented beers and then single-fermented lagers. This is because the repeated fermentation process modifies the protein, known as LTP1, in a way that reduces the surface tension between individual bubbles, making them less likely to burst.

In single-fermented beers, the LTP1 proteins are small and densely packed on the bubble surfaces, providing some resistance but not enough to keep the foam stable. In double-fermented beers, the proteins form a two-dimensional structure, giving the thin liquid films an elastic quality that helps them last longer. Meanwhile, in triple-fermented beers, the LTP1 proteins break down into fragments with both water-repellent and water-loving ends, further stabilizing the bubbles.

The researchers believe their findings could help brewers create beers with more long-lasting foam, either by increasing the number of fermentation steps or by manipulating the LTP1 proteins. However, they acknowledge that foam is not equally important everywhere, as it is primarily a cultural preference, especially in Belgium.