Does Fermenter
Geometry Affect Beer Quality?
Author: Joe Dunleavy
July 2012
Does
fermenter geometry affect beer quality? I make beer in different fermenters all
the time and I often wonder if different flavor profiles occur with different
fermenters. I’ve brewed long enough to have a collection of different vessels
to ferment in: (conical, carboys, better bottles, buckets). I’ve even fermented
in a stainless steel square. When I bought the conical I went with the fourteen-gallon
capacity as opposed to the seven-gallon capacity. I bought the larger conical
so I could ferment both five and ten gallon batches. I usually ferment five-gallon
batches and wonder if the yeast acts differently than the ten-gallon batches.
With the five-gallon batches the majority of the wort is located in the cone of
the conical. Does the fermenter’s shape, size, pressure on yeast, affect the
flavor profile? Can anyone really tell the difference between beers fermented
in different vessels?
I
listen to various podcasts and read every magazine and book I can find on
brewing. I’ve read and heard various things about fermenter geometry affecting
the flavor profile, but most of this material pertained to the commercial
level. The research that I have reviewed on the homebrew level just had too
many uncontrolled variables for me to feel comfortable with. Does the yeast in
my small batch size act the same as in a large commercial vessel?
I
reached out to some home brewing royalty in hopes of getting some information
based on some of their comments I’ve heard over the years. I emailed Gordon
Strong and Jamil Zainasheff hoping to get some feedback on my fermenter questions.
I also mentioned an experiment I was thinking of performing regarding
fermenting the same beer in different vessels. Gordon responded to my email and
volunteered to evaluate my beers if I performed the experiment. Jamil stated he
would review my experiment as well. I then
mentioned my experiment to a coworker named Mike Guth who just became a BJCP
judge. Mike thought that some of his brew club members would be interested in
my experiment, particularly David Houseman. Mike then asked David if he would like
to review the beers as well. David said he was in.
All
of a sudden, I had three top members of the home brewing scene to review my
beer. I’m not a BJCP judge so I thought this was a great development, but I was
a bit intimidated sending my beer out to reviewers of this caliber. I also knew
I couldn’t pass up this opportunity. Thank you to the reviewers for taking the
time to review my experiment. I was amazed at your willingness to share your
time and knowledge with another home brewer. Thank you for all each of you does
for home brewing!
Here are the details on the fermenter
experiment. Each
batch was brewed and fermented in my brewery. The yeast I decided to
perform the experiment on was a German Hefeweizen strain. I felt the German
Hefeweizen strain would be a good candidate because yeast manufacturers
document that the flavor profile can be altered. However, I haven’t seen anything
documented about altering the flavor profile by changing the fermentation
vessel.
My
brewery capacity is not large enough to do this in one boil so I ended up
brewing three different times on two different days. The two different days
were a week apart and the weather on both brew days was about the same.
Brewery
capacity mandated three separate batches and boils.
Here
is each batch and a description of each fermentation vessel:
Batch
1 (D,E,B): better bottle, carboy,
and 1/2 conical
Batch
2 (A,F): full conical, open
ferment 4G
Batch
3 (C): bucket
A
– 9 gallons in a fourteen-gallon conical
B
- 4.5 gallons in a 14-gallon conical
C
- 4.5 gallons in a 6.5 gallon bucket
D
- 4.5 gallons in 6-gallon Better Bottle
E
- 4.5 gallons in a 6.5-gallon carboy
F
- 3.75 gallons in a 4.5 gallon 6" deep open stainless steel pan - loosely
covered with tinfoil during ferment and sealed with tinfoil as fermentation
slowed.
The
following parameters were the same:
·
grain sacks
·
grain percentages (50% German wheat, 50% German pilsner)
·
mash temperature rests(120,152,160,168)
·
boil time (90min)
·
ibu level(13.4) - same hop batch from Hop Union
·
carbon filtered water
·
water treatment (calcium 91, magnesium 5, alkalinity as CAC03 30, sodium
20, chloride 98, sulfate 94), Residual alkalinity -38 - sulfate to chloride
ratio balanced
·
oxygen level - 60 seconds of bottled oxygen
·
original gravities(1.046)
·
finishing gravities (1.012-1.013)
Each
fermenter was sanitized with the same 5-gallon batch of an acid based sanitizer
cycled between the fermenters. Each batch received one fresh package of German
Hefeweizen yeast. The full conical received two fresh packages because it was
twice the volume of the other batches. I normally would create a starter, but
took that variable out of this experiment. This resulted in a slight under
pitch of yeast, but I was more interested in the flavor profile differences than
making the best Hefeweizen to style.
Each
batch was pitched at 60 then held at 62 for a week in a fermentation chamber.
The temperature controller probe was against the conical cone insulated
with bubble wrap. Each batch was fermented in the same fermentation chamber (a
converted freezer). The yeast blew through fermentation in a few days. An
interesting note is that krausen formed at different times between the
fermenters with batch E starting a few hours before D or B. Batch A, F, C seem
to krausen at the same time. After a week, the fermenter was moved out of
temperature control into a room temperature environment and the yeast dropped
out naturally. Then each batch was siphoned or transferred under CO2 to a
CO2 purged keg and carbonated to approximately two volumes. Each batch was then
bottled off the keg into new, washed and sanitized bottles. The bottles and
bottling equipment were sanitized with an acid based sanitizer prior to each batch
bottle fill.
My tasting notes:
I
tasted these beers directly from the keg. I used coded cups without knowing
which beer was which. I did a taste test at 38 degrees and did not pick up many
differences between (A,B,D,E). C and F were different with F being the odd
ball. I was sure that F was the open ferment. I then let the beers warm up
10 minutes and did a second taste test.
This
is when I could pick up the differences better.
Batch
A (full conical): Clove, banana
Batch
B (half conical): less clove and banana than A but fruitier, clearer
Batch
C(bucket): dull, thin, slight puckering
Batch
D(better bottle): clove, banana, tastes a lot like A, clearer than others
Batch
E(carboy): Balance of clove, banana, clearer than others, preferred
Batch
F(open ferment): Huge fresh sour dough yeast, mouth puckering. This is a
different beer than A-E - something got in this.
I
then looked at the labels and tasted each beer again because I wanted to compare
A and B, D and E, A and D. I preferred A over B - different flavors. I
preferred E over D - close though. I preferred D over A - close though.
Batch
C was thinner tasting than other beers - maybe oxygen pickup from bucket or
something else. Batch F was like sticking my head into fermenting sour dough
bread. Could this have been wild yeast?
My
preferences were E, D, A, B, C, F.
Jamil Zainasheff tasting notes:
I
would rank the beers in terms of fermentation quality: E B D A C F
E
has a lighter fruity character and balancing clove. Some malt character and
much better head form and retention. Clearly the best fermented of the bunch,
but not necessarily a fantastic hefeweizen. I could drink a pint of this.
Others
exhibited various forms of sulfur and acid (C F).
Some
very high banana and juicy fruit character (B).
F
was undrinkable, it was down right horrible. Acetone, sourness, and a fart
stink.
C
wasn't much better. It was sour and exhibited signs of skunkiness.
David Houseman tasting notes:
A
- banana, clove, light, smokey
C
- lager like, less banana and phenols, bright
B
- bit less banana & phenols than A but more bitter and astringent
E
- lemon, clove, not as much banana/ester as A & C. Medicinal, lemon
rind
D
- dull, lemon, less banana clove, some coconut notes, oxidized
F
- off, diacetyl, dms, fusels.
Gordon Strong tasting
notes:
All
styles had similar color (light gold) and clarity (some haze).
A:
strong perfumy notes, noticeable banana. most intense of all the samples.
probably the cleanest/purest of flavors and strongest aromas. med-full
body. clean flavor matching aroma (banana, spice/clove/pepper). My clear
favorite, 1st place.
B:
moderate perfumy aroma, not totally clean -- slightly dirty/funky, hint of
sour. medium body. moderate banana and spice with light solvent. 3rd place.
C:
moderately low perfumy notes. Clean, just subtle. Over time, the aroma faded
and became less clean; hmm. Full body. Clean flavor, subtle, mild fruit
and spice. 5th place (3rd place earlier before the aroma died).
D:
moderately strong perfumy notes. clean, mostly banana with a hint of solvent.
full body. mild fruit and spice, clean flavor similar to sample C. Finish has a
touch of acidity/sharpness/alcohol, which gave it a slight bite that balanced
the malt. 2nd place.
E:
moderately low perfumy notes. Not totally clean -- a little dirty. Kind of like
a bad homebrew hefeweizen (warm ferment). Full body. Some increased
phenol/solvent. Moderate banana. More spice than others. Slight acidity.
4th place.
F:
low perfumy notes. quite neutral in the nose; not much aroma at all.
medium-full body. a little snappy in the flavor -- green apple? moderate
banana. had the most acidity. not too clean, sharper in finish, hint of
vinegar? most unpleasant aftertaste. My clear bottom, 6th place.
So
the 1st and 6th places were pretty obvious to me, while the other ones could
easily move up or down relative to each other depending on the moment. The
overall intensity of the aroma varied quite a bit. Surprisingly, the body
seemed to have some differences as well. Also saw the acidity change
between samples.
I
thought E had the highest phenols, and F had the most issues. I focused on the
differences since there were very many similarities.
Note:
Gordon tasted the sample 4 weeks after everyone else.
Preference comparison:
David: A, C, B, E, D, F
Gordon: A, D, B, E, C, F
Jamil: E, B, D, A, C, F
Joe
: E, D, A, B, C, F
I
was surprised with the results. I expected all the reviewers to pick the same
first and last beer, but that did not occur. My expectations were that the full
and half conical would taste the same, they didn’t. I expected the similar
shaped vessels (carboy, Better Bottle, bucket) to produce the same flavor
profile, they didn’t. Each flavor profile was similar across batches, but they
were differences in each one. It was kind of like attending a family picnic; you
know you’re all related but each one is different in their own special way.
So
what does all this mean to me? It was clear to me that beers do differ when
fermented in different vessels. I now
can utilize fermenter shape as a variable during fermentation to work towards a
particular flavor profile. This experiment has also opened up a few new
questions for me. This experiment was performed with a Hefeweizen strain and it
performed differently between the fermenters. Can other saccharomyces yeast
strains be manipulated to alter the flavor profile? Does brettanomyces produce
different flavor profiles when fermented in different vessels? How do bacteria
(pediococcus, malolactic, and lactobacillus) behave in different vessels? How
does your favorite yeast behave when different fermentation vessels are used? I
would suggest conducting your own experiment with your favorite yeast and see
where it takes you. You might be surprised with the results as well!
