by Alain Schepers Blogger at Bierista.nl
Why does beer have a head?Part 1 of the two part series on head
What a beautiful sight! A nice glass of beer with a creamy head on top. It almost makes you thirsty just thinking about it. But why does beer have a head? Where does it come from and does it serve a purpose? As a beer lover, you’ll almost certainly be curious about these questions.
First the question: where does the head come from?
The brewing process uses grains, which contain proteins. During brewing, the grain is cooked up into a soup, which makes wort, a sort of porridge rich in sugars and proteins. The coarse proteins are filtered out of the wort, and the remnants are the brewer’s spent grain. These proteins make this grain popular as cattle feed. Later on the finest proteins are processed - consumed - by the yeast. It’s mainly the medium sized proteins which are important for the head on the beer.
Carbonated bubbles are the basis of the head. Carbon dioxide is formed by yeast cells. The carbon dioxide in the beer is realised in the form of bubbles, which rise to the surface. On the way, they pick up the aforementioned medium sized proteins, which form a sturdy protective layer on the bubble. Thanks to this protein, the bubble lasts for longer in beer than it does in a glass of coca cola or sparkling orange.
What is a head good for?
This is a seemingly simple question which requires a lengthy answer. The foam is a sort of blanket on the beer. It protects your beer. The head is a lid that prevents the carbonation from escaping too quickly; without it, that refreshing tingle wouldn’t last long at all.
That same head also protects your beer against air. It forms an airy layer over your beer, preventing it from oxidising too quickly. Oxygen can affect the flavour of the beer, and the head stops this from happening. Oxidised beer is not nice; it turns those refreshing aromas into the smell of cardboard and old paper.
The sturdiness of a head is of the utmost importance. You want to keep that white blanket on your beer for as long as you can. This can be measured: experts do this by means of measuring the time it takes for the head to decrease by half. If the time is 110 seconds or more, you’ve got a good head on your beer.
The brewer’s skills
The head can tell you something about the skills of the brewer. If your beer has an uneven head with large and small bubbles in it, the brewer probably doesn’t have their process completely under control. Many brewers like to add wheat malts to their beer. A small quantity results in a better head. Sometimes there’s a lot of head upon opening the bottle; foam might spurt out even if you haven’t shaken the bottle. These excessively foamy beers are known as gushers. When this happens, it means something has gone wrong with the raw materials or during brewing or bottling.
Carbon dioxide - nitrogen
Beer foam is naturally made of carbon dioxide, although nitrogen can also be used to achieve a good head. This results in foam with small, fine bubbles. This compact foam is incredibly robust and almost resembles whipped cream with its thick and creamy appearance. Anyone who’s ever enjoyed a Guinness on draught knows how tasty a head made from nitrogen can be.
By no means do all beers have to have a full head. English beers, for example, are well known for this. The English don’t particularly like head and would rather have a nice full glass of beer. There’s nothing wrong with these beers - they’re a part of British beer style and culture. Other sorts of beer, such as Geuzes, aren’t known for their white caps either. So don’t judge a beer for not having a proper head: there are styles of beer where a creamy head just doesn’t fit.
We’ll be back with more on foam. We’ll give you some practical tips on how to serve beer with the perfect head.
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