Why Does Beer Foam?

Photo: Behance

Whether you refer to it as foam, head, kräusen or the junk on top of your beer—love it or hate it—the foam that develops on top of mostcraft beers is impossible to ignore. But what is it, exactly? How can foam differ from glass to glass and beer to beer? Why is your beer foamy, but not the one served to the person sitting next to you?

Behind beer foam’s mysterious curtain there is actually a lot of science!

Foam Basics

When beer foams, it is obviously due to the creation of bubbles. This phenomenon is referred to as nucleation.

Photo: Food & Wine Magazine

The physics of nucleation as a whole isn’t entirely understood, and there are a large group of proteins and smaller polypeptides (additional proteins) that can act as a group and individually as foam positive agents. One particular protein naturally found in barley is Lipid Transfer Protein 1 (LTP1), and it plays a large role in a beer’s foam.

LTP1 has a high rate of “hydrophobicity” (meaning it doesn’t like water), so in order to help alleviate its predicament, it grabs hold of a bubble of CO2—produced in fermentation as well as introduced in bottling/kegging—and then rises to the surface alongside the CO2 bubble (or N2, for nitrogen beers…but more on that in a bit).

Once at the surface, the LTP1 protein forms a coating on the bubbles which helps maintain the foam. Hops also come into play as the hydrophobic polypeptides derived from grain cross link with bitter iso-alpha acids from hops to render foam more ridged, stable and clingy.

There are dozens of variables that impact the differences in head-foam quality, texture and retention, but quantities of LTP1 in a specific batch of beer can be traced back to factors like how wet or warm the climate was that produced the barley.

Foam’s Effect on Flavor

A beer often tastes different when it’s topped with head of foam, and this is due to surface active compounds that move into the bubble walls as they percolate to the top of your glass. Foam also carries a profound trigeminal sensation—that is, “taste” effects which are actually perceived physically. Think of the “cool” sensation of mint, or the “hot” sensation of chili peppers. Neither is delivering an actual thermal load, but rather they cause a physical perception. The creamy, fluffy feel of foam can dramatically alter the perception of any given beer by “softening” the overall palate.

It’s also important to remember that our senses of taste and smell are intimately interwoven. In fact, many times a specific characteristic that a drinker may describe as ‘taste’ is actually detected in their nasal passage. Foam brings more odor compounds to the surface of your beer, kind of like un-stuffing your nose and opening up the full range of flavors.

What is Lacing?

Photo: Eater

The LTP1 proteins mentioned earlier, which form a coating around every foam bubble, interact with other compounds that also happen to rise to the top of your glass.

Once these proteins and compounds begin to interact with one another, they become denser, undergoing a textural transition, and begin to stick to the sides of the glass when left alone for a bit. This is why a beer consumed slowly will accumulate much more lacing than its guzzled counterpart.

Why tilting a beer glass to avoid foam actually makes you bloated

(Business Insider) The correct way to pour beer is by tilting the glass and pouring with vigour

If you’ve ever tried your hand at bartending only to realise you are unable to pour a beer without forming a head of foam - you are in luck.

A beer sommelier has revealed to Business Insider the proper way to pour a beer - and it turns out that a head of foam is actually a good thing when enjoying a nice cold one.

According to Max Bakker, the first and only Master Cicerone in New York - a certification which means he has an exceptional understanding of all things beer related - without that collar of foam, a beer is not a beer at all.

And beer bloat is actually the result of pouring a beer incorrectly - or pouring a beer with minimal foam.

According to Max, carbon dioxide that has not been released into a glass when pouring a beer, which is what happens when you pour beer into a tilted glass slowly, has a disastrous effect when it settles in your stomach.

This slow-pour means the CO2 has nowhere to go - which leads to bloating when the liquid is disturbed in your stomach and the remaining carbon dioxide is released - especially once you add food to the mixture.

The solution? Pouring a beer down the side of a glass with vigour.

This method of pouring a beer ensures that the CO2 is broken out into the glass - meaning the bloating that occurs when drinking a beer that was not poured properly doesn’t happen.

So before you try to send back a beer for having too much foam, remember that the foam is actually protecting you from feeling full and uncomfortable.

The foam always turns into beer anyway, according to Max.

And the foam is where “you will taste the sweetness of the malt and the bitterness of the hops” as well as protect the integrity of the beer aroma.

*******READ MORE: National Beer Day - Why, When & How to Celebrate - Bizarre Holidays

Top 10 Rose Wine to Drink in 2021/2022 Pretty in pink, rosé wine is an exciting and diverse category. Check out the list of 10 must-try suggestions for rose wine of 2021 below!

The 11 Best White Wines To Drink In 2021/2022 Wine is an integral part of human history, and it’s hard to refuse a drink, especially if it’s a glass of bubbly and refreshing white ...

The Best Red Wines To Drink In 2021/2022 There's so much red wine choice on the shelves nowadays it's easy to get overwhelmed by the options. Here in KnowInsiders, we have gathered the ...

National Beer Day In USA: Why It Is Celebrated, List of All Beer Drinking Get your wallet, grab a glass and call your friends to gather around the local pubs, or stay at home with a six pack! National ...