No, Tapping on a Beer Can Doesn't Stop It From Fizzing Over
Apologies to that one friend who keeps using this "trick" to not lose out on any beer.
If you drink canned beer, you've probably heard this advice: Give the can a few taps to prevent it from foaming over when you crack it open. I've even heard specific variations on this technique. Don't tap it on the top; tap it on the sides: That's what really works. Well, good news for old wives: You can apparently add this one to your list of tales. According to new (legitimate) research out of Demark, tapping your beer can does absolutely nothing.
In a paper that sounds like a rejected project from your high school science fair, a research team out of the University of Southern Denmark published, "To beer or not to beer: does tapping beer cans prevent beer loss? A randomised controlled trial." But despite the silly name, the study does present some valid points as to why such research is a worthwhile venture. "Preventing or minimizing beer loss when opening a can of beer is socially and economically desirable," the paper begins, later adding, "Fizzing reduces the amount of beer available for consumption and results in waste. Beer spray can also stain clothes or surrounding objects." Bingo.
Sadly, however, researchers ultimately conclude, "Tapping shaken beer cans does not prevent beer loss when the container is opened." But getting there was no small feat. The study looked at 1,000 cans of pilsner-style beer (generously donated by Carlsberg which was otherwise not involved in the research) broken into four relatively equal groups: unshaken/untapped, unshaken/tapped, shaken/untapped, and shaken/tapped. The shaking was handled by the Heidolph Instruments Unimax 2010, which shook the cans for two minutes at 440 rpm. The tapping "was limited to three single-finger flicks on the side of the can," always in the same place, "the recycling label printed on the side of the can." The paper states, "To maintain consistency, only one of the team members tapped the cans throughout the experiment." Hopefully, whoever got stuck with that boring job was also the first to be allowed to drink the leftover brews.
Each can was weighed both before and after opening, and overall, tapping made "no statistically significant differences." Shaken cans lost an average of about 3.5 grams of mass—or about a ninth of an ounce of liquid—regardless of tapping. Meanwhile, unshaken cans lost about 0.5 grams of mass (A.K.A. less than you would ever notice).
In the end, the authors explain that, based on their findings, "The only apparent remedy to avoid liquid loss is to wait for bubbles to settle before opening the can." However, the story doesn't necessarily end there. The researchers also hypothesize that one aspect that could explain their results is the composition of beer itself. Beer contains specific types of proteins that "may prevent the microbubbles from rising to the top of the can after tapping" which also "explains why the foam head is more stable for beer than for carbonated drinks that lack these foam-stabilizing proteins… Therefore, we cannot assume an identical result to a soda experiment."
So until we can find researchers willing to shake and flick 1,000 cans of soda, feel free to keep tapping your Mountain Dews. That rumor has yet to be officially debunked.