Thursday, March 17, 2011

The Secret to a Frothy Stout

Here's your annual "how does draft Guinness work?" article, courtesy of LiveScience. This one describes a new twist on the old widget:

Applied mathematicians in Ireland recently discovered a possible replacement for the widget that is not only eco-friendly, but could be cost-effective for brewers. They published their findings in the Mar. 8, 2011, issue of the journal Nature.

Graduate student Michael Devereux, supervised by William Lee of at the University of Limerick in Ireland, discovered that microscopic plant fibers can froth stout as well as a widget.

"Our proposed alternative to the widget would consist of an array of cellulose fibers of approximately three square centimeters," said Devereux. "Our research suggests that stout could be made to foam using an array of fibers in 30 seconds, which is the time it typically takes to pour a glass of stout."

Inside of a nitrogen-enriched stout, pockets of air trapped inside cellulose fibers become seed bubbles that trigger nucleation (the formation of additional bubbles). As nitrogen and carbon dioxide diffuse through the walls of the fibers, the seed bubbles grow. When each bubble reaches a certain length, it detaches and breaks off of the gas pocket and floats to the top of the liquid. This process is repeated until the gas dissolves completely into the stout.

Read the whole story at LiveScience and at Nature, where one of the researchers says, ""We've spoken to brewers, but we're not sure if they're interested yet."

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