Science Questions

What makes Guinness® or stout so dark?

Sun, 7th Oct 2007

Listen Now    Download as mp3 from the show Brewing and Alcohol

Question

Alexis Waldo asked:

What makes Guinness® or stout so dark, thick and foamy and so good compared to the lighter, clear beers that you get elsewhere and places like the US?’

Answer

We put this question to Charlie Bamforth, Professor of Beer and Brewing at the University of California at Davis.  You can hear the whole interview here.

Well, there are many excellent beers, some of them very light, some of them very dark. The colour of Guinness® is due to roasted cereal, roasted barley. They have a very intense heating process. The sugars and the amino acids and the grains are cooked together to give very, very dark colours. They give very roasted flavours. The foam: one of the main reasons why Guinness® foams so well is, apart from CO2 producing foam, they use nitrogen gas to give it extremely stable foams. The bubbles contain nitrogen gas and this is much more stable than CO2. Guinness® pioneered that technology.

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