Nitrogen and CO2. Pressure and solubility. Nucleation and bubbles. And why some beer cans have a beer can widget in them.
How can we keep the beer in a beer can tasting fresh? Why, all we need to do is to have balls!
If you have no idea what I am talking about, pick up a beer can such as those produced by Guinness, Old Speckled Hen, Young’s Double Chocolate Stout, Murphy’s Stout, and Boddingtons Pub Ale, and give it a good shake. Or even better, cut it open, and you will see a small ping pong ball-looking thingy inside called a beer can widget.
How does this beer can widget keep beer tasting fresh? Beer tastes fresher when there is a thick and creamy head. This head is formed because of the pressurized carbon dioxide (CO2) found in the can of beer.
The pressurized CO2 occupies less volume than what would occupy at normal atmospheric pressure. When we open a can of beer, the pressure quickly drops to atmospheric pressure. The CO2 expands and escapes as little bubbles that form the foamy head.
The secret then to fresh tasting beer is to have more bubbles that can form the thick and creamy head. We can create more bubbles by providing more nucleation sites. Nucleation is the
“…process in which a change of state … occurs in a substance around certain focal points… [such as] the appearance of gas bubbles in a liquid.” (Source: Wisegeek)
These focal points are known as nucleation sites.
This is where the beer can widget comes in. The widget is filled with compressed nitrogen and beer. It also has a little hole in it.
When the can is popped open and the pressure drops, the
“… compressed gas inside… quickly forces the beer out through the tiny hole into the can. As the beer rushes through the tiny hole, [it provides more nucleation sites and] this agitation causes the CO2 that is dissolved in the beer to form tiny bubbles [see video above]…” (Source: How Stuff Works and Guinness Youtube)
The sharper ones amongst you might in turn ask “how did the nitrogen and beer get into the widget in the first place?”. Watch the start of the above video again: the widget is filled with nitrogen to begin with and dropped into the can. In addition, nitrogen is also introduced into the beer as “a small shot of liquid nitrogen [which] evaporates during the rest of the canning process”.
As it evaporates, and because it is not very soluble, it pushes the beer into the widget and compresses the nitrogen already inside, priming them to jet out of the widget when the beer can is popped.
The widget need not be a ball. Take a look at the video below to see how other shapes and ways!
Like this? We can keep your head fresh like a beer can widget, so like me to discover more! All you need is a minute a day to explore the world’s marvels through the phenomenon of food!
photos: in order – depositphotos/Erdosain; By The original uploader was Duk at English Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons; depositphotos/Aguaviva; pogonici