It’s happened to all of us: a beer shows up with way too much foam and way too little actual beer. Yes, in America, we expect a little foam in our beer mug. But anything more than the usual inch of froth, and we feel we’ve been short-changed. In other beer cultures, though, the opposite sentiment is true. Foam is something that is very much desired—and even expected.
Scientists call the formation of foam nucleation, and there’s a long, drawn-out explanation of how and why it happens. The short version: Grain-based proteins grab hold of the beer fizz and ride it all the way up. There, the proteins join alpha acids to make the foam strong and sticky.
Other things contributing to the mass of foam are the surrounding temperature, the type of glassware and any possible contaminants. Glassware that isn’t “beer-clean” (detergent-free) can inhibit foam formation, as can lipstick, lip balm or food grease on the drinker’s lips. On the other hand, a glass that’s grooved on the inside can increase the amount of CO2 bubbles and bolster head. One way to produce copious amounts of head on any beer is to pour it into a frozen mug. The ice on the inside of the mug is like Miracle-Gro for bubbles.
As mentioned before, an inch of foam at the top of a beer is the expected depth. It’s ideal for myriad reasons. Foam, also called head or krausen, carries with it volatile oils that contribute to aroma and even taste. Since the senses of taste and smell are so tightly linked, the aromas trapped in the foam are transferred to your olfactory receptor—your nose—as you raise a glass of beer to your lips. The resulting stimulation improves your enjoyment by providing clues to your taste buds and even enhancing the actual flavor of the beer.
Czech and Japanese beer cultures prize foam and often seek to increase its depth. The makers of the world’s first pilsner beer, Pilsner Urquell, have developed three distinct ways to pour their beer, each with a different foam profile. The Hladinka (smooth) has a thick layer of foam, three to four inches; the Na Dvakrát (crisp) is more in line with what we Americans expect at the top of a brew, and the Mlíko pour (milky) is mostly foam, with a small amount of beer at the very bottom.
The Japanese like frothy beer so much, they’ve created special devices to ensure lots of foam. The Jokki Hour is a stein with a lever on the handle that creates a thick foam head when pressed. If you don’t want to splurge for a whole stein, the Koku-Awa peripheral clips to a beer can and creates plenty of creamy head as the beer is poured into a glass.
Whether you like a lot or a little, one thing’s true: Beer foam is natural and should be a desired asset. After all, everybody likes a little head.