How to Make a Foamier Beer
Home Brewing Recipes
Baker Street Ales Associate Brewer
Arny Lands
Beer Nexus
the crossroads of the beer world
Instead of giving you a recipe this month I thought you might be
interested in some of the new thoughts on home brewing,
specifically, how to make a foamier beer.

As you can imagine I have to read quite a bit about brewing for
my job.  A couple of weeks ago I came across a study by
scientists from Australia and Spain in the Journal of Agricultural
and Food Chemistry in which they reported finding a gene (and
characterized the transcribed protein) in a particular yeast strain
that made the resultant beer foamier. This is the first time
scientists have ever done so.

While knowing the identity of a particular yeast gene that
promotes foaming isn't going to be of much use to most home
brewers -- unless you are a dab hand at creating recombinant
yeast strains, in which case, have at it -- it's of interest to the
greater brewing industry because understanding the creation
and retention of a head on a glass of beer is an important quality
control technique. The quality of foam on a pint is one of those
things that consumers notice and subsequently use to,
consciously or not, judge your beer.

So, what is beer foam? At its most basic, beer foam is a thin film
of liquid, stabilized by various molecules including hop-derived
organic acids and glycoproteins, around a volume of gas. Those
glycoproteins--proteins with attached sugar groups--come in
many forms, but today we are primarily interested in those called
mannoproteins.

That is, each protein chain has many mannose--a six-carbon
sugar very similar to glucose--molecules attached to it. The
protein part of the glycoprotein is mostly hydrophobic, while the
mannose side-groups with their myriad -OH groups are
hydrophilic. This dissimilarity between the two parts of the
molecule is key to foam stabilization: the hydrophobic parts line
the interface with the carbon dioxide gas, while the hydrophilic
sugar groups hold onto a bit of the water in beer and keep the
walls of the foam intact.  

For a long time, brewing scientists thought that the primary
source of those glycooproteins was malted barley. This makes
sense, because one goes through two distinct processes in
brewing to try to force most of that protein out of the beer: the
hot break and the cold break. The hot break is kind of like when
you make egg drop soup: the uncooked egg hits the hot water,
the proteins in the whites denature, and the whole thing
"cooks." The cold break at the end of the boil forces other
proteins to precipitate out of solution. Both sets of gunk are
removed from the wort during filtering and while the beer settles
in the primary and secondary fermenter. But even with all of this
filtering, a lot of protein--including mannoproteins and the
glutens that give celiac patients such grief--still floats in the
beer. And those proteins are responsible for that froth on the
top of your beer glass.


Over the last few years, a series of papers has reported that
some of the mannoproteins responsible for foam stability don't
come from the barley at all. They come from the yeast. Basically,
as the beer ages and the yeast start to die, some of them
autolyze (self-digest), and components of their cell walls--the
mannoproteins--end up free-floating in the beer. So it seems the
claims that yeast proteins are crucial to beer foaming
characteristics in all types of beer are decidedly true.

But if you like lots of foam--maybe because you think it helps
concentrate the hop aromas or it just feels right on the
palate--you could probably replicate their results. The strain that
the scientists say they used was Weihenstephan 34/70--a strain
of yeast from Weihenstephan Abbey brewery, which at 972 years
old claims to be the oldest continuously operating brewery in the
world.

You can get the Weihenstephan 34/70 in dry form from Safale as
Saflager, or from Wyeast as 2124 (Bohemian lager) or White Labs
as WLP830 (German lager). Happy foaming!


                      
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    Good Brewing and Cheers!

            Arny Lands
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