Beer foams less when you tilt the glass: Science explains why

Foam is physics and chemistry. Physics first, because it is a very special state of matter, made up of gas bubbles dispersed in a liquid; Chemistry too, because for these bubbles to “hold up”, they need an ally, which we call a “surfactant” which can be of a very diverse chemical nature. In the kitchen, we often come across lecithin and proteins that will do the job very well for making traditional soufflés, meringues or even the famous foam that has recently appeared on our plates.

Because for there to be foam, not only must there be bubbles, but they must also, above all, be stable enough so that they bunch up against each other without bursting. Thus, soft drinks, just like so-called “sparkling” wines, reveal their fizz as soon as the bottle is opened, releasing carbon dioxide (CO) in the form of bubbles.₂) which is dissolved there: it actually “foams”…and again when you pour the drink into the cup…but this foam disappears almost immediately!

So, what “more” is there in beer that allows its bubbles to stay on the surface for so long, forming that famous white collar that fans enjoy? Surfactant! In fact, the proteins in the malt as well as isohumulone (a molecule resulting from the breakdown of lupulin provided by hops during fermentation) surround the bubbles as they rise, forming a protective layer that allows them to clump against each other. Before finally exploding several minutes later.

Now that we understand the chemistry, how can we “control” the foam volume? Returning to physics: because the more the liquid is moved, the greater the volume of gas released. This is why beer served high in the glass will produce a lot of foam, while by letting it flow very gently (and thus without shock) along the glass, the foam will remain thin. However, is it a good idea to do this? Obviously, because any gas that isn't released during service will be released… by turmoil in your stomach! For the same reason, it is not recommended to drink directly from the bottle. Either way, bloating is guaranteed during the digestion process!

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