The theory behind the technique is that tapping the can will break up bubbles of carbon dioxide. Without tapping, those bubbles swell and rise to the surface, causing spillage.
However, new research from the University of Southern Denmark in Odense tested the theory and turns out tapping doesn't actually make a difference.
“Being a scientist, I always wanted to know whether it actually has an effect,” says Elizaveta Sopina from the University of Southern Denmark in Odense.
Using more than 1000 330ml cans of Carlsberg, scientists put half the beer through a mechanical shaker for two minutes, intended to simulate transport via bicycle. After dividing the cans into shaken and half shaken, they then "tapped" (flicking them on the side three times) half of both groups.
Tappers were unaware of which cans had been shaken. All cans were weighed before and after to help measure how much beer was lost in the process.
Shaken cans, on average, lost 3.45g of beer on opening while just .51g was lost from unshaken cans. Interestingly, tapping didn't make a significant difference to spillage.
Sopina puts this down to beer containing barley proteins that stabilise bubbles - proteins that help prevent bubbles from rising to the top of the can.
Her suggestion to avoid extra foaming? “If you want to save your beer, let it settle,” Sopina says.
