I remember the first time I bought Guinness Draught in the can. My first thought was, “Who screwed up?” But then I examined the can and realized that the little ball in my empty can must be a result of the most brilliant minds of science (beer science) for the purpose of simulating Guinness off the tap. I was right. But not knowing how something works bugs me, and I am guessing bugs a lot of other beer drinkers. So here’s whats in your beers:
Typically beer is carbonated with CO2. In the can this CO2 is in the beer itself, and in the can. That’s why when you pop the top of a canned beer it goes, “pshhhht.” That is the preassurized CO2 that rests on the surface of the beer escaping the can. When the CO2 escapes, it agitates the beer, as does the action of pouring, causing some of the CO2 mixed in the liquid to escape. You see this in the form of the head that floats on top of your beer. (Don’t worry, even though I know the science behind it I too still like to refer to it (head) as “magic.”
Beers like Guinnes and Wexford were traditionally pub brews, only available in the pub. They are creamier and substantially less carbonated than a canned lager. Off the tap, the substanital pressures of the tap mechanism ensure a heady pour, but in the can, Guinness is preasurized with CO2 and Nitrogen. While CO2 easily dissolves into the beer, Nitrogen does not. The pour out of the can results in a far-from-pub experience.
To better appeal to their customers at home (and to increase their competitive edge) Guinness, as far back as 1968, began the inventive proccess that has led to the floating widget you see (or hear) today. This floating widget, this marvel of human ingenuity, is a capsule of different shapes and sizes depending on the producer, that contains carbon dioxide and nitrogen dioxide. These gasses are released as the can is opened, infusing the beer and creating the ambiance consumers desire.
Without the widget, your Guinness, or Wexford, or Bodingtons, would just be a mostly fizzless, headless, creamy beer. This isn’t really a huge deal to me, but given the choice, I’ll take the widget!