Welcome to brain stuff. From how stuff works, Hey, brain stuff, Lauren vocal 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. Both are carbonated and poured from a bottle, can, or fountain. So why does beer form ahead 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 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. 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 ahead of foam.
The formation of this foam, 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 where the 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, 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 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 it more difficult to pop. 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 ops iso alpha acids, further lend stability to the phone. Even with the potential for all these bubbles to stick around, 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 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 outlast sodas no matter how it's poured. Today's episode was written by Lauriel Dove and produced by Tyler Clang. For more this and lots of other bubbly topics, visit our home planet, how Stuff Works dot com.