The question immediately catches the eye: while A glass full of beer as soon as he paid he immediately shows a thick, creamy foam, capable of resisting for minuteseven while drinking, A can of Coca-Cola behaves differentlysince the opening gives a few seconds of effervescent foam, which disappears in a momentleaving only the thin bubbles to go back to the surface.
A curious phenomenon, which has passionate about craft beers lovers, like physicists and chemicals who study carbonated drinks. The explanation is in fact concealed inside a Perfect balance between proteins, carbon dioxide and natural surfactants present in raw materials.
What happens with beer
In beer, The foam was born thanks to the carbon dioxide produced naturally during fermentation, which remains in solution under pressure. When you pay beer, The pressure decreases, the CO₂ molecules quickly free themselves and form the bubbleswhich go up to the surface, creating the characteristic foam head. But the only one is not enough to guarantee the resistance of the foam: the proteins present in malt and hopscapable of stabilizing bubbles, creating a membrane that holds carbon dioxide and prevents the bubbles from breaking immediately.
The role of proteins, in fact, is fundamental for the stability of the foam. Among these, Malto proteins bind to the acid hops of hops (responsible for the beer amaro), forming an elastic lattice around the bubbles. The result? A persistent and compact foamwhich is renewed with each sip, also maintaining the cooler beer, reducing the dispersion of carbon dioxide and protecting the most delicate aromas.
Coca Cola’s behavior
In Coca-Cola and other sugary carbonated drinks, the situation is completely different. Here too the CO₂, added artificially, is released when the can opens or when the drink is paid, generating a short foaming. The fact is that There are no stabilizing proteins and natural surfactants that keep the bubbles integralreplaced by sugars, aromas and dyes which, although they can influence the viscosity of the liquid, do not form resistant structures capable of supporting the foam. Coca-Cola foam is therefore formed, but it dissolves quicklyleaving space only to the bubbles that continue to go back to the surface and to vanish one after the other.
The effect is also linked to type of carbon dioxide present and bottling pressure. Craft beers often have a more moderate and natural level of carbonation, while industrial carbonated drinks are loaded with a high amount of CO₂ to obtain a more lively feeling on the palate. The greatest pressure facilitates the formation of bubbles quickly, but these, without a “protective network”, break quickly.
For anyone who wishes to deepen with an authoritative source, this Live Science article clearly explains how proteins (albumins) and carbon dioxide work together to make beer foam more persistent than that of carbonated drinks, which are lacking.
Other reasons
Another factor concerns glass and cleaning of the glass. A dirty glass of fats or residues of detergents reduces the formation of foam in beer, because succulent substances break the protein membranes that stabilize bubbles. Those who love beer know this detail well: A clean glass is the first step to get a perfect and lasting foam. In the drinks, however, the foam is formed regardless of the state of the glass, but it vanishes anyway, because the structure of the bubbles does not have adequate protein support.
It is no coincidence that, In beer culture, foam is considered an integral part of the tasting experience. It protects perfumes, helps to modulate the perception of carbon dioxide on the palate and offers a visual experience that accompanies the drink. In carbonated drinks, effervescence serves to give a feeling of freshness and liveliness, but does not become part of the taste as in beer.
Cheers!
