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Speaker 1: Welcome to brain Stuff, a production of iHeartRadio. Hey brain Stuff,

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Speaker 1: I'm Lauren vogel Bomb, and this is a classic episode

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Speaker 1: of the podcast. In this one, we get into the

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Speaker 1: exciting science of foam. No really, it's a fascinating phenomenon

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Speaker 1: air bubbles holding their shape and a liquid. So what

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Speaker 1: allows something like beer to hold on to those bubbles

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Speaker 1: whereas the foam on a glass of soda dissipates? Hey,

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Speaker 1: brain Stuff, Lauren vogl Bomb. Here, pour a soda into

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Speaker 1: a glass and it will foam, But those tiny bubbles

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Speaker 1: quickly die down. Beer, on the other hand, will form

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Speaker 1: a foamy head that sticks around long after it's been poured.

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Speaker 1: Both are carbonated and poured from a bottle, can or fountain.

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Speaker 1: So why does beer form a head but soda doesn't.

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Speaker 1: There's a lot going on in that foamy beer head

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Speaker 1: from the delicate interaction of gas and protein to alcohol content.

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Speaker 1: Beer is complex, and we don't just mean the flavor.

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Speaker 1: Like it or hate it. Beer foam is a preview

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Speaker 1: of what you're about to imbibe. As each beer bubble

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Speaker 1: releases an aroma, the scent begins to influence your perception

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Speaker 1: of the beverage and wet your anticipation as you prepare

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Speaker 1: to drink it. A plus, a dense head of foam

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Speaker 1: can make a beer feel more creamy and flavorful. Beer

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Speaker 1: is in fact the only alcoholic beverage that will form

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Speaker 1: and maintain a head of foam. The formation of this foam,

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Speaker 1: also known as nucleation, involves a complex reaction of proteins.

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Speaker 1: This includes large protein molecules and their smaller cousins polypeptides.

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Speaker 1: One protein specific to barley malt, which is used in

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Speaker 1: the brewing of beer, is worth a closer look. It's

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Speaker 1: called lipid transfer protein one, or LTP one, and it

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Speaker 1: has a serious aversion to water. To escape the wet stuff,

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Speaker 1: it will use a bubble of carbon dioxide as a

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Speaker 1: life preserver. Thankfully, for LTP one, there are a lot

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Speaker 1: of life preservers because CO two is produced in abundance

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Speaker 1: during the fermentation of beer, and it may also be

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Speaker 1: introduced during bottling. As LTP one clings to the carbon

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Speaker 1: dioxide and rises to the surface, it will form a

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Speaker 1: protective coating around the bubble that makes more difficult to pop.

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Speaker 1: This helps beer maintain its head far longer than a

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Speaker 1: soda or hard cider, but it's not the only factor

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Speaker 1: at work. Additional hydrophobic polypeptides bond with compounds that enter

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Speaker 1: the beer courtesy of the hops. That beer usually contains.

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Speaker 1: The hop's iso alpha acids further lend stability to the foam.

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Speaker 1: Even with the potential for all these bubbles to stick around,

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Speaker 1: a foamy head isn't a sure thing. A beer has

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Speaker 1: a sweet spot an alcohol content of about five percent

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Speaker 1: Too high or too low, and the foam will dissipate

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Speaker 1: more quickly. Keep in mind that beer foam would be

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Speaker 1: nothing without a glass in which to reach its full potential.

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Speaker 1: The next time you drink a frothy glass of ale,

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Speaker 1: take a closer look at that vessel. Are there nearly

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Speaker 1: imperceptible scratches on the inside of the glass? Is there

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Speaker 1: a brand logo etched into the glass's interior, perhaps at

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Speaker 1: the bottom. This interruption of the flat surface creates a

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Speaker 1: nucleation site, a series of cracks and scratches designed to

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Speaker 1: encourage bubbles to continue to form and rise. These special adaptations,

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Speaker 1: paired with beer's penchant for foam, mean its head will

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Speaker 1: outlast SODA's no matter how it's poured. Today's episode is

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Speaker 1: based on the article why does beer form a head

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Speaker 1: but soda doesn't on how stuffworks dot Com written by

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Speaker 1: Loriel Dove. Brain Stuff is production by Heart Radio in

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Speaker 1: partnership with how stuffworks dot Com and is produced by

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Speaker 1: Tyler Klang. For more podcasts my heart Radio, visit the

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Speaker 1: your favorite shows.