Stout beer, with its tiny bubbles and legendary head, requires special equipment to be poured out correctly. A new team thinks that people could get the same result by dirtying the beer up.

Stout beer enjoys a special reputation. It's dark, has a particular taste, and is topped by a creamy foam unmatched by other beers. The reason for its special taste and consistency is chemical. While most beers are foamed up using carbon dioxide; stout gets a lot of its fizz from nitrogen. Although nitrogen is a fine gas, responsible for sixty percent of the earth's atmosphere and the tiny creamy bubbles in stout, it has some drawbacks. Chief among these drawbacks is the fact that it does not dissolve as readily as carbon dioxide, so there's less overall gas in the beer.


People don't usually like their beer flat, so when stout is served it is put through a device that gases up the beer before it hits the glass. Sure, the problem is solved, but it's solved expensively, so something has to be done. New knowledge comes to the rescue!

For a long time, the continual fizziness of alcohol and soda was chalked up to the release of the pressure it was under in the container. Gas was forced to dissolve into the liquid, it was kept under pressurized conditions in the container, and once released it would just keep bubbling up and out of the liquid. That turned out not to be the case. Maybe the initial popping of the top would cause the liquid to fizz, but if it were poured into a perfectly clean container, it wouldn't bubble. The fizziness of drinks is a result of tiny pieces of grit in the container. In a bar, or in most homes, there might not be a lot of dirt in a container, but there is cellulose. Cellulose are little strings of plant material from the rag or paper towel that the glass was wiped with. These pieces of cellulose come with small amounts of air, and that air provides the seeds for bubbles.

Not all the gas is going to find its way to a piece of cellulose, meaning that there is still some gas left dissolved in most beers. Although stout may be low on gas, if it's high on microscopic pieces of cellulose, more gas will get together with fiber and more gas will bubble readily upwards. The researchers who figured this out calculated that as little as nine square centimeters of an ordinary coffee filter will allow stout to be as bubbly as ever.


Via The Economist.

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