Speaker 1: Welcome to brain Stuff, a production of iHeartRadio. Hey brain Stuff,
Speaker 1: I'm Lauren vogel Bomb, and this is a classic episode
Speaker 1: of the podcast. In this one, we get into the
Speaker 1: exciting science of foam. No really, it's a fascinating phenomenon
Speaker 1: air bubbles holding their shape and a liquid. So what
Speaker 1: allows something like beer to hold on to those bubbles
Speaker 1: whereas the foam on a glass of soda dissipates? Hey,
Speaker 1: brain Stuff, Lauren vogl Bomb. Here, pour a soda into
Speaker 1: a glass and it will foam, But those tiny bubbles
Speaker 1: quickly die down. Beer, on the other hand, will form
Speaker 1: a foamy head that sticks around long after it's been poured.
Speaker 1: Both are carbonated and poured from a bottle, can or fountain.
Speaker 1: So why does beer form a head but soda doesn't.
Speaker 1: There's a lot going on in that foamy beer head
Speaker 1: from the delicate interaction of gas and protein to alcohol content.
Speaker 1: Beer is complex, and we don't just mean the flavor.
Speaker 1: Like it or hate it. Beer foam is a preview
Speaker 1: of what you're about to imbibe. As each beer bubble
Speaker 1: releases an aroma, the scent begins to influence your perception
Speaker 1: of the beverage and wet your anticipation as you prepare
Speaker 1: to drink it. A plus, a dense head of foam
Speaker 1: can make a beer feel more creamy and flavorful. Beer
Speaker 1: is in fact the only alcoholic beverage that will form
Speaker 1: and maintain a head of foam. The formation of this foam,
Speaker 1: also known as nucleation, involves a complex reaction of proteins.
Speaker 1: This includes large protein molecules and their smaller cousins polypeptides.
Speaker 1: One protein specific to barley malt, which is used in
Speaker 1: the brewing of beer, is worth a closer look. It's
Speaker 1: called lipid transfer protein one, or LTP one, and it
Speaker 1: has a serious aversion to water. To escape the wet stuff,
Speaker 1: it will use a bubble of carbon dioxide as a
Speaker 1: life preserver. Thankfully, for LTP one, there are a lot
Speaker 1: of life preservers because CO two is produced in abundance
Speaker 1: during the fermentation of beer, and it may also be
Speaker 1: introduced during bottling. As LTP one clings to the carbon
Speaker 1: dioxide and rises to the surface, it will form a
Speaker 1: protective coating around the bubble that makes more difficult to pop.
Speaker 1: This helps beer maintain its head far longer than a
Speaker 1: soda or hard cider, but it's not the only factor
Speaker 1: at work. Additional hydrophobic polypeptides bond with compounds that enter
Speaker 1: the beer courtesy of the hops. That beer usually contains.
Speaker 1: The hop's iso alpha acids further lend stability to the foam.
Speaker 1: Even with the potential for all these bubbles to stick around,
Speaker 1: a foamy head isn't a sure thing. A beer has
Speaker 1: a sweet spot an alcohol content of about five percent
Speaker 1: Too high or too low, and the foam will dissipate
Speaker 1: more quickly. Keep in mind that beer foam would be
Speaker 1: nothing without a glass in which to reach its full potential.
Speaker 1: The next time you drink a frothy glass of ale,
Speaker 1: take a closer look at that vessel. Are there nearly
Speaker 1: imperceptible scratches on the inside of the glass? Is there
Speaker 1: a brand logo etched into the glass's interior, perhaps at
Speaker 1: the bottom. This interruption of the flat surface creates a
Speaker 1: nucleation site, a series of cracks and scratches designed to
Speaker 1: encourage bubbles to continue to form and rise. These special adaptations,
Speaker 1: paired with beer's penchant for foam, mean its head will
Speaker 1: outlast SODA's no matter how it's poured. Today's episode is
Speaker 1: based on the article why does beer form a head
Speaker 1: but soda doesn't on how stuffworks dot Com written by
Speaker 1: Loriel Dove. Brain Stuff is production by Heart Radio in
Speaker 1: partnership with how stuffworks dot Com and is produced by
Speaker 1: Tyler Klang. For more podcasts my heart Radio, visit the
Speaker 1: airheart Radio app, Apple Podcasts, or wherever you listen to
Speaker 1: your favorite shows.