BrainStuff Classics: Why Does Beer Foam Last Longer Than Soda Foam?

Beer and soda both form sudsy bubbles when you pour them, so why does soda's foam dissipate while beer's forms a head? Learn about foam physics in this classic episode of BrainStuff, based on this article: https://science.howstuffworks.com/innovation/edible-innovations/beer-form-head-not-soda.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeartRadio. Hey brain Stuff,
I'm Lauren vogel Bomb, and this is a classic episode
of the podcast. In this one, we get into the
exciting science of foam. No really, it's a fascinating phenomenon
air bubbles holding their shape and a liquid. So what

(00:23):
allows something like beer to hold on to those bubbles
whereas the foam on a glass of soda dissipates? Hey,
brain Stuff, Lauren vogl Bomb. Here, pour a soda into
a glass and it will foam, But those tiny bubbles
quickly die down. Beer, on the other hand, will form
a foamy head that sticks around long after it's been poured.

(00:45):
Both are carbonated and poured from a bottle, can or fountain.
So why does beer form a head but soda doesn't.
There's a lot going on in that foamy beer head
from the delicate interaction of gas and protein to alcohol content.
Beer is complex, and we don't just mean the flavor.
Like it or hate it. Beer foam is a preview

(01:05):
of what you're about to imbibe. As each beer bubble
releases an aroma, the scent begins to influence your perception
of the beverage and wet your anticipation as you prepare
to drink it. A plus, a dense head of foam
can make a beer feel more creamy and flavorful. Beer
is in fact the only alcoholic beverage that will form
and maintain a head of foam. The formation of this foam,

(01:26):
also known as nucleation, involves a complex reaction of proteins.
This includes large protein molecules and their smaller cousins polypeptides.
One protein specific to barley malt, which is used in
the brewing of beer, is worth a closer look. It's
called lipid transfer protein one, or LTP one, and it
has a serious aversion to water. To escape the wet stuff,

(01:49):
it will use a bubble of carbon dioxide as a
life preserver. Thankfully, for LTP one, there are a lot
of life preservers because CO two is produced in abundance
during the fermentation of beer, and it may also be
introduced during bottling. As LTP one clings to the carbon
dioxide and rises to the surface, it will form a
protective coating around the bubble that makes more difficult to pop.

(02:11):
This helps beer maintain its head far longer than a
soda or hard cider, but it's not the only factor
at work. Additional hydrophobic polypeptides bond with compounds that enter
the beer courtesy of the hops. That beer usually contains.
The hop's iso alpha acids further lend stability to the foam.
Even with the potential for all these bubbles to stick around,

(02:32):
a foamy head isn't a sure thing. A beer has
a sweet spot an alcohol content of about five percent
Too high or too low, and the foam will dissipate
more quickly. Keep in mind that beer foam would be
nothing without a glass in which to reach its full potential.
The next time you drink a frothy glass of ale,
take a closer look at that vessel. Are there nearly

(02:53):
imperceptible scratches on the inside of the glass? Is there
a brand logo etched into the glass's interior, perhaps at
the bottom. This interruption of the flat surface creates a
nucleation site, a series of cracks and scratches designed to
encourage bubbles to continue to form and rise. These special adaptations,
paired with beer's penchant for foam, mean its head will

(03:14):
outlast SODA's no matter how it's poured. Today's episode is
based on the article why does beer form a head
but soda doesn't on how stuffworks dot Com written by
Loriel Dove. Brain Stuff is production by Heart Radio in
partnership with how stuffworks dot Com and is produced by
Tyler Klang. For more podcasts my heart Radio, visit the

(03:37):
airheart Radio app, Apple Podcasts, or wherever you listen to
your favorite shows.