Is yeast presence a major head retention inhibitor?

Good foam is something that many brewers like on their brews for
aesthetic and mouthfeel reasons. Foam looks appetizing on top of a pint
of brew and also adds texture to the beer when drinking. Some draught
beers have really creamy foams created by using nitrogen to froth up
the beer. We use nitrogen for certan styles at Springfield Brewing
Company and I love the effect on some beers, but getting great foam on
a nitrogen-dispensed beer is much easier than from a carbonated beer.

There are several things that can cause beer foam to be less than
remarkable. Some of the real foam killers frequently seen in brewing
are compounds that actively cause beer foam to collapse. Most of these
substances have one thing in common and that is that they congregate on
the surface of the beer and compete for space with beer foam at the
gas-liquid interface.

Lipids (fats and oils) and surface-active cleaners/sanitizers are
two types of substances that really do damage to foam. While lipids
usually do not come from brewing ingredients, they are frequently found
on beer glasses that have either been soiled by lipstick or dirty
dishwater. This is really more common than most people think when
drinking beer at a bar. You can also transfer grease to a beer glass
when you are munching on oily snacks — for example, peanuts or potato
chips — while sipping a beer.

Most soaps and sanitizers have surfactants to aid in their
effectiveness and residuals of these compounds can cause foam problems.
This is one reason that it is so important to rinse cleaners from
brewing tools. If you use non-rinse sanitizers, it is very important to
make sure that your sanitizer of choice does not damage beer foam. If
you are not sure whether you’re using a sanitizer that damages foam you
can do an easy test. Rinse one glass with water and one glass with
sanitizer. Allow both glasses to drain upside down for 15–30 seconds so
the surface is not completely dry. Pour a half bottle of beer from the
same bottle in a similar fashion into both glasses to ensure foam
formation and watch. If the foam in the glass rinsed with sanitizer
crumbles like the Berlin Wall you’re using a wicked sanitizer!

The beer itself has intrinsic properties that dictate the ability
for good foam formation. In my experience with foam, the most important
foam positive constituents of beer are proteinaceous compounds from the
malt. Although the use of under-modified malt in brewing comes with a
whole set of issues and is really hard to find, the breakdown of barley
proteins during germination is limited and there is a relatively large
amount of foam-positive protein in the malt. In contrast, well- and
over-modified malts are fairly common and protein degradation in these
malts is more extensive during malting (protein degradation is one of
the key parameters used to gauge modification).

The bottom line is that malt modification affects foam and most of
the pale malt on the market today is well-modified and has less foam
positive proteinaceous goodies than lesser modified malt. Some brewers
have strong feelings about the importance of proteolytic activity
during mashing; there are those who know it happens and how it affects
beer and those who know that it really doesn’t happen and see it as a
waste of time. Believers in proteolytic activity during mashing caution
against a long rest around 122 °F (50 °C) because it can reduce the
foam quality of the resulting beer.

Adding some wheat malt to a brew can make up for the deficit in
foam-positive proteins from barley malt because wheat malt contains
much more foam positive compounds compared to barley malt. Although
many recipes call for a small amount of wheat malt (about 5%) intended
to improve foam, I have never found that this small amount does much
for the beer. Our best seller is an unfiltered American-style wheat
beer made using about 50% wheat malt and about 7% raw wheat. This beer
has a very different foam appearance and stability compared to our
all-barley malt beers.

Our unfiltered wheat also contains yeast and I have never noticed
much of a change in foam stability over time after bottling. Yeast can
cause problems with beer foam over long storage periods because when
yeast die and autolyze, enzymes spill into the beer. Proteolytic
enzymes are included in this spilling and degrade foaming proteins in
the beer. As you mention in your question, Belgian beers are known for
really nice foam, and they are normally bottled conditioned. I do not
think your foam problems come from yeast in the bottle.

In addition to protein, hops are also considered foam positive
because beers brewed with almost no hops have poorer foam stability
compared to beers brewed with perceptible bitterness. This is more of a
laboratory-type observation and most beers have enough hops to benefit
from their foam positive nature. Adding more hops to improve foam
affects flavor and while it is true that really hoppy beers often have
good foam I cannot recommend using hops as a foam enhancer and a
solution to bad foam in general.

The gas content of beer, normally carbon dioxide, clearly
influences foam because there would be no foam without gas evolution
upon dispense. Carbon dioxide content primarily influences foam volume
and not foam stability. So if you increase the carbon dioxide content
of beer, you may have more foam initially but the rate of collapse will
not be affected. Like adding more hops I don’t suggest adjusting your
carbonation rate based on improving foam; the carbonation content
affects flavor and you should shoot for a target in-line with the beer
you are brewing.

Some beer glasses contain little etched spots in the bottom that
act as nucleation sites for bubbles to form. This causes the continual
formation of foam while the beer sits in the glass and new foam formed
replaces foam that has collapsed. Some people add a few pieces of
coarse salt to the beer and these little chunks of salt do the same
thing as the special etched spots. Samuel Adams (Boston Beer Company)
recently came out with a special glass they developed to enhance the
presentation of their beers and one of the design features is a little
etched spot in the bottom.

There are some ingredients used in certain brews that are believed
to either be outright foam negative or at least have the potential to
be foam negative. One common theme of such ingredients is the presence
of lipids and examples include flaked oats, chocolate, coffee, vanilla,
nuts and other nutty brewing ingredients. Although these ingredients
contain more oil than malted barley (sometimes considerably), they do
not necessarily cause foam problems. They can, however, and brewers
need to look out for problems when using such ingredients. Your stout
contains flaked oats and many brewers believe that oats cause foam
problems.

I think what Chris Colby meant when he stated that adding a bit of
wheat malt should not be a substitute for sound brewing practice is
that there is not a silver bullet to brewing beer with good foam. All
the factors that affect foam must be considered to appease the foam
gods.

Response by Ashton Lewis.