Julien Behal / AP file
A customer drinks a pint of Guinness, in the Gravity bar at the Guinness storehouse, Dublin, in this file photo.
On St. Patrick's Day, many a pensive imbiber will shake their empty can of Guinness stout and hear the rattle of the widget that gave their beer a foamy head. That idle pleasure could come to an end. Now, a patch of cellulose fibers is all that's needed to get the magical foam, according to new research.
The makers of Guinness started adding the widget to cans of Guinness Draught in the 1980s. The plastic device sits in the top of the can and when the can is opened, the widget spews nitrogen and beer. This helps give the canned stout the same foamy head and creamy mouth feel as a pint poured in a pub.
Researchers at the University of Limerick previously showed that when champagne and other carbonated drinks are poured in a glass, bubbles form as the liquid hits fibers of cellulose — essentially dirt — on the surface of the glass.
"The cellulose fibers will either have been shed from the cloth used to wipe the glass dry or will have fallen out of the air," William Lee, a lecturer in mathematics and statistics, who led the research, writes in a Q&A about the findings.
Applied to stout
The team, however, thought this mechanism didn't apply to stout because when a canned stout without a widget is poured in a glass, bubbles didn't form. This was thought to be due to the fact that nitrogen is added to stouts to reduce the acidity brought on by carbon dioxide.
But to double check, they put an intern on the case who found that bubbles do form, albeit much more slowly. To see the bubbles, watch the video below.
Bubbles form in stout beer.
The team notes that stouts have a mix of carbon dioxide and nitrogen. Nitrogen gives the small bubbles that make the nice creamy head, but the bubbles grow much more slowly. To make the bubble formation in stouts faster, but without the use of a widget, the researchers propose lining the top of cans with a 2.9 centimeter square of fibrous material positioned so that the stout flows past it as it is poured out of the can, according to Lee.
In a pub, Guinness is dispensed at high pressures through a plate with tiny holes in it, Lee explains. The resulting turbulence creates the tiny bubbles that are created by a widget in a can. The widget, Guinness says, gives canned beer the taste and texture of a pub-poured pint at home.
"Maybe this new idea will give them a replacement for the widget," Mark Denny, author of "Froth: The Science of Beer," told me today. "Time marches on and this may or may not be a less expensive alternative."
Is Guinness best in Ireland?
All this thinking about the science of beer and Guinness in particular leads to another, perhaps more subjective, question that has occupied drinkers of the creamy stout for decades: is a pub-poured pint of Guinness the same all around the world?
Yes, according to the brand's Website. "We always use pure, fresh water from natural local sources for the Guinness stout brewed outside Ireland. That said, in blind tests (with a bunch of highly cynical journalists) none of our sample could tell the difference between Irish-brewed Guinness and the locally produced variety."
That sample must not have included Daniel Kotz, Liam Glynn, Christian Mallen, or Jochen Cals, a group of researchers from different countries who traveled around the world to collect data on the enjoyment of Guinness. They found it is indeed best in Ireland.
As they traveled and sampled Guinness at various pubs, they rated their enjoyment on a "Visual Analog Scale" from 0 (enjoyed it not at all) to 100 (enjoyed it very much). A total of 103 tastings were recorded (42 in Ireland, 61 elsewhere) in 71 pubs spread over 33 cities and 14 countries. The enjoyment of Guinness in Ireland scored higher, 74 on the scale, than outside the country, 57 on the scale.
"This difference remained statistically significant after adjusting for researcher, pub ambience, Guinness appearance, and the sensory measures mouth feel, flavor, and aftertaste," the teams writes in the March 1 issue of the Journal of Food Science.
"This study is the first to provide scientific evidence that Guinness does not travel well and that the enjoyment of Guinness (for our group of nonexpert tasters) was higher when in Ireland. Results, however, are subject to further verification because of limitations in the study design," they add.
Denny, who has a PhD in theoretical physics from Edinburgh University and is a fan of Guinness, agrees that "Guinness in Ireland tastes better than Guinness anywhere else … but I wouldn't say it is due to the fact that it doesn't travel well necessarily because, for example, Guinness brews its beer in other parts of the world."
Rather, he suspects the beer is tweaked to suit local tastes. The Guinness poured in Ireland is "thicker, got more body to it, (and) that beautiful head on top is so thick it is almost like meringue," he said.
More stories on the science of alcoholic drinks:
- How to pour that drink, scientifically
- Building a better bar bot
- Happy (hic) birthday, canned beer!
- Ancient Nubians drank beer laced with antibiotics
- Space beer headed for zero-gravity bar
John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).