One of the most famous dry stouts (Guinness) has nitrogen gas dissolved in it instead of carbon dioxide.

• A. Oxygen
• B. Carbon Dioxide
• C. Helium
• D. Nitrogen

Answer: (D)

The key idea is how the gas dissolved in beer shapes its texture and head. Nitrogen makes for a very smooth, creamy mouthfeel because it forms much smaller bubbles than carbon dioxide. Because nitrogen is less soluble in beer, it doesn’t produce as sharp a carbonation bite, so the beer feels softer and the head stays dense and velvety. That creamy head and smooth sensation are exactly what the Guinness pour is famous for. In cans and on draught, a nitrogen widget or careful pressurization releases nitrogen to create that distinctive cascading pour and creamy head. If carbon dioxide were driving the fizz, you’d get a crisper, more prickly carbonation and a lighter head, not the same silky mouthfeel Guinness aims for.