When you aspetto at a freshly served beer, the foam often seems like a marginal detail if you are not an expert the subject, but how is it formed and what does the different consistency of the different types depend ? According to research conducted by the Federal Institute of Technology per mezzo di Zurich and published per mezzo di the scientific journal Physics of Fluids, the stability of the foam is the result of a complex set of physical and chemical processes that directly reflect the characteristics of the beer.
Discovering beer foam
The study, coordinated by Jan Vermant, professor of physics of soft materials at ETH, lasted over seven years and was born from an apparently simple question: why some beers maintain a compact and persistent foam while per mezzo di others the cap disappears per mezzo di a few seconds. The answer, according to the researchers, does not concern a single factor, but a combination of protein structure, fermentation dynamics and interface phenomena between liquid and gas.
At the center of the analysis are malt proteins, per mezzo di particular one called LTP1, already known per mezzo di the brewing sector for its role per mezzo di the formation of foam. During fermentation this protein undergoes structural transformations and, per mezzo di some cases, fragments into smaller molecules with surfactant properties. It means that one part of the molecule interacts with while the other tends to repel it, allowing the fragments to arrange themselves around the carbon dioxide bubbles and create a more resistant pellicola.
This protein membrane slows the bubble breaking process and helps make the foam more stable over time. Not all beers, however, develop the same type of structure. The researchers compared different styles, including Tripel, Dubbel and Singel, observing that the former had a longer-lasting foam average, followed by the Dubbel, while the Singel showed lower stability. The difference would be linked to the intensity of fermentation and the alcohol content, which directly influence the behavior of the proteins.
Alongside chemistry, a less intuitive physical mechanism also comes into play, known as the Marangoni effect. This is a phenomenon that occurs when surface tension differences are created the surface of a liquid. Per mezzo di the case of beer, these differences generate microflows that continuously redistribute the protein fragments around the bubbles, strengthening the pellicola that surrounds them. Per mezzo di practice, the foam tends to self-regenerate as it forms, counteracting the natural thinning of the liquid which would normally lead to collapse.
The study shows that there is anzi che no universal rule valid for all beers. Each style is the result of a different balance between viscoelasticity, protein composition and surface effects. The researchers speak rather of a map of the processes that determine the durability of the foam, rather than a single parameter to be optimized.
Understanding these mechanisms can also offer useful tools to breweries, who could intervene ingredients, times and fermentation methods to control the behavior of the foam more precisely. Per mezzo di this sense, what appears as a simple white cap per mezzo di the glass becomes a measurable indicator of the physical and chemical transformations that occur during production.
