Coatings may hold the secret to an age-old quest: how to pour a stout beer with a perfect head.
So say mathematicians at Ireland’s Mathematics Applications Consortium for Science and Industry, who are publishing a chemically dense treatise on their intoxicating findings.
“Bubble nucleation in stout beers,” by William Lee and colleagues, appears on the pre-press website arxiv.org and is to be published in the journal Physical Review E.
No Kick Like Champagne
The researchers set out to discover why stout beers, such as Ireland’s legendary Guinness, lack the same foamy bubbles as champagne, sparkling wines and carbonated beers.
In those weakly supersaturated solutions of carbon dioxide, “bubbles grow and detach from nucleation sites: gas pockets trapped within hollow cellulose fibers,” the team writes. “This mechanism appears not to be active in stout beers that are supersaturated solutions of nitrogen and carbon dioxide.”
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When canned, stout beers require additional technology, or widgets, to release the bubbles that will form the head of the beer. Without the widget, the beer looks flat when poured.
Nitrogen added to the dark beers gives them a creamier head but—even with a widget—substantially slows the bubble nucleation process.
Coffee Machine Science
The solution, the mathematicians say: Add a coating of hollow porous fibers to the inside of the can or bottle. The team has even tested the theory and, so far, it holds.
“We poured stout over some filter paper from the departmental coffee machine, looked at it under a microscope, and saw bubbles forming in the fibers,” Lee told the Australian website ABC Science.
The group found that a single fiber produced one bubble every 1.28 seconds, the website said. At that rate, the group calculated that about four million cellulose fibers would be needed to produce a good head of beer—the equivalent of a three-centimeter square of coffee filter paper.
Applying a fiber coating inside the beer can above the line of liquid could therefore serve to create a rich, foamy head of bubbles as the stout is poured, Lee told the website.
That could eliminate the need for brewers to add widgets, he said.
“Widgets are very cheap to manufacture and deploy, but they still add a small cost to the production of a can of stout,“ he told ABC Science. “Another problem is removing oxygen from the widgets, which is time consuming. If oxygen from the air is left in the widget, it will react with the beer, affecting its flavor.”
More research would need to be done, but Lee says the idea is worth investigating: “The global sales of stouts are so huge that even tiny savings could add up to quite significant profits.”