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HOMEBREW Digest #4891
HOMEBREW Digest #4891 Thu 17 November 2005
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
Digest Janitor: pbabcock at hbd.org
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Contents:
Home Brewery Pictures ("Randy Pressley")
re esters/fusels 1. ("steve.alexander")
more re esters/fusels ("steve.alexander")
Re: Need advice -- All-grain system ("Sean Richens")
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Date: Thu, 17 Nov 2005 09:09:03 -0500
From: "Randy Pressley" <RANDYP at cityofws.org>
Subject: Home Brewery Pictures
I thought it would be interesting to see folks brewery setups.
I made this a few months ago.
http://www.geocities.com/randypressley/HomeBrewery.html
My objectives were the following:
Eliminate the need to lift heavy mash tun's and brew kettles.
Make it easier to brew.
Save space.
Have one place where all my brew stuff is located.
The side tables can be folded down and I have wheels on the unit so I can
easily roll it around.
I don't brew outside like the picture suggests, but just inside my garage.
This protects the burners from wind and the contaminents from getting
into the brew kettle, like falling leaves. But outside takes a better picture.
Randy Pressley
Winston-Salem, NC
Member of the WortHawgs Brew Club since 1995
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Date: Thu, 17 Nov 2005 19:41:54 -0500
From: "steve.alexander" <steve-alexander at adelphia.net>
Subject: re esters/fusels 1.
Sorry - my reply to Matt Baumgart bounced FOUR times and so the
conversation is all out of sequence.to.
Matt Baumgart wrote:
>>>>Steve mentions a startling result regarding esters--that
>>their production is independent of temperature if oxygen is
>>controlled. My first reaction is "where can I read more about
>>this?" Steve is there a reference available?
This appears in BY&F pg 425 ( a shorthand for "Brewing Yeast and
Fermentation", by Chris Boulton and David Quain, Blackwell Science
Press, 2001, great book for the HB science geeks btw). Sadly they
don't give reference. They describe for a paragraph how higher temps
imply less soluble oxygen, and that less oxygen implies less sterol,
which implies less growth, and when the growth terminates with amino
acids and fermentables remaining this implies esters will be
synthesized.
BY&F finish their paragraph with ... "In fact, it may be shown that
yeast growth extent and beer ester concentrations are unchanged at
different temperatures when oxygen concentration is maintained at a
constant value". I think that last sentence is a stunner, but there is
no further citation in that section of the book. I'll have the check
the other chapters.
>> Thus, after a few hours the ferment temp has little/no effect of
>>ester production!?
That's probably true, and also starting - good thought Matt ! I will
point out that fusels increase dramatically with temperature and their
formation is dependent on amino acid concentrations and temperature
and they are formed from pitching till the point of growth cessation
at a high rate. VDKs and autolysis also havre temp dependent features.
>>>>2. I believe from reading certain studies that production of
>>>>fusel-derived esters has some real dependence on the levels of the
>>>>associated fusel. If this is true, and if the result Steve
>>>>reported applies to fusel-based esters, then presumably production
>>>>of FUSELS is also independent of temperature when oxygen is
>>>>controlled!? (And thus also independent of temp after the first
>>>>few hours...)
Sorry to burst your bubble, but the fusels do increase with temp. The
fusels are a necessary pre-req for forming esters, but they seem to
*not* play the primary role in the rate of ester formation under
"normal" circumstances". There is a two enzyme conversion to
transform acetylCoA+ fusel into an ester+CoASH, and the AAT enzyme is
only expressed under certain conditions.
Fusels are a different story. Fusels happen when the yeast consume
amino acids and then decarboxylate the intermediate keto-acid part
forming an aldehyde which is reduced to a fusel alcohol. They can get
a little energy from this exercise, but it seems like a metabolic
"mistake" in the sense that usually makes more sense to use the keto
for amino acid formation than to make toxic fusels while producing a
little energy. It's likely that the fusel formation at higher temps is
related to increased permeability of low quality cell membranes. If
you choose a good strain and keep them "fat", you *may* not experience
a fusel problem.
>>3. This means that (at least as far as esters and maybe fusels go)
>>we don't have to care about fermentation temps. We only have to
>>care about the PITCHING temp, and maybe not even that if we can do
>>some extra aeration.
Only esters - the fusels will still increase with temps. Also note
that oxygen is only one possible non-sugar growth limiting factor. If
you have any non-sugar growth limitation esters will likely forms.
Just another little side note on esters - adding 50mg/L (50ppm = 1
gram per 5gallon batch (about 1/4 teaspoon)) of linoleic to a
fermenter in one study decreased ester formation by 80%. One
explanation is that the yeast absorb the linoleic so they synthesize
less fatty acids and then don't need to strongly esterify the lipid
synthesis pathway to remove toxic FAs. It would be interesting to see
if adding this amount, or perhaps half that amount radically decreased
esters in a warm ferment.
As a flavor control for warm ferment also consider the old
"top-pressure" technique. A very interesting topic for another post.
-S
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Date: Thu, 17 Nov 2005 20:20:03 -0500
From: "steve.alexander" <-s at adelphia.net>
Subject: more re esters/fusels
>>>>I assume that by this you mean that someone has shown that fusel
>>>>production does increase with temp even when oxygen is controlled?
Not exactly. Many people have shown that fusels increase with temp w/o
controlled O2 level. Other show that higher O2 (o2 vs air saturation
levels in wort) cause roughly doubled fusels. What you are suggesting
is that tho' increased O2 and increased temp each individually
increase fusels, that the combination doesn't. That's hard conclusion
to arrive at without evidence.
I'll post a bit on this later, but modern commercial lager brewing
uses something like this cool-pitch/warm ferment approach to reduce
the fermentation time.and there are undoubtedly papers showing
volatile metabolites.
>>>>If we control for oxygen, why should the cell membranes be of
>>>>lower quality, [...]
In a nutshell, there are good reasons to think that the fusels will be
at least reduced when the initial pitching is cooler as compared to
the case where the pitch & fermentation are both warm. Still I expect
that this will produce more fusels than cool-pitch/cool-ferment. A
test is called for more than further speculation.
>>>>Who knows! Are Boulton and Quain available by email so we can ask
>>>>them about the ester result and where it comes from, and whether
>>>>it might also apply to fusels?
I intend to ask them about the remarkable and unreferenced quote, but
I will not ask researchers to become librarians for my convenience.
Most books note that fusels increase with temps and give references.
B&Q cite Barker et al, MBAA-TQ v29,pp11-17 as a primary reference on
fusels vs temp. Here is the abstract
http://www.mbaa.com/techquarterly/abstracts/1992/tq92ab06.htm B&Q also
note that the temperature relationship wrt fusels is something of a
mystery. If they could state more unequivocally they would have
published it.
Other sources, like Kunze, note that warm pitching specifically
increases fusels. Kunze also notes that warmer fermentation leads to
more fusels.
>>>>In the meantime, I still have to think that *if* the ester result
>>>>is true, there is reason to believe it might apply to fusels as
>>>>well.
I doubt this is the case.
You should read the papers on fermenting under "top-pressure". The
impact is strain dependent, but often the pressure causes a dramatic
decrease in ester levels and only a modest decrease in fusel levels.
Also look for papers by Arayapaa and others circa 1970. It's possible
to completely avoid or exaggerate almost any specific fusel by
"doctoring" up the level of the related amino acids throughout
fermentation.
Many many papers show that ester level is radically reduced when
exogenous sources of fatty acids (trub, tween-80, linoleic) are
introduced. Also dramatically increased when growth is blocked.
The major factor controlling fusels is FAN level vs yeast status,
while esters are most related to yeast state at the end-of-growth
phase related to lipid synthesis. More fusels do not necessitate
more esters except in the case where we control "other factors".
Temperature introduces a bucket-full of "other factors".
>>>>But, it looks from some studies like addition of fusels or
>>>>associated aminos leads to some increase in associated esters,
Yes. This study matches my expectation - increasing the fusel
concentration causes an almost linear increase in the related ester
formation under otherwise similar conditions until saturation around
800ppm of fusels (fig 7). This matches Michaelis-Menten equations for
an enzyme mediated conversion. [[ Of course no one will drink a beer
with much over 100ppm of total fusels]].
Even though the fusel level is approximately linearly related to fusel
concentration this is NOT the controlling ester factor in brewery
fermentation. Instead it's the the amount of the specific AAT enzymes
available due to fermentation conditions.
You are looking at a lesser controlling factor Matt (most beers have
50-100ppm of fusels regardless), rather than the 10X larger factor of
yeast condition leading to AAT enzymes and esters.
Back to perspective - The one paper indicates a 15% increase in fusels
w/ a 6C increase in temp. The most I've seen in a paper is a 19%
increase over 4.5C and these are without oxygen control. Perhaps with
cool pitching this percentage drops a fair bit. That's not a
show-stopper but be aware that fusels will *likely* increase with
temperature.
>>>>If fusels increase dramatically with temp (with oxygen
>>>>controlled), then at least in some cases I'd expect SOME increase
>>>>in their associated esters. This doesn't happen if the ester
>>>>result is true.
It's a fair guess that the esters concentration is always (almost)
linear wrt to the fusel level *IF* all other conditions are identical.
The problem is that we know that "other conditions" can cause factor
of 10X type variations in ester level for a given fusel level and we
do not understand these "other factors" perfectly. You are reasoning
backward from a volatile result to the main course. You are trying to
make statements about the dog's trajectory by watching the the wagging
tail. You might be right, but it's very thin ice.
Let me give you a *hypothetical* counterexample Matt. Lets assume
that two O2 controlled ferments at different temps produce identical
ester levels yet the hi-temp pitched one has a 1.5 times the fusels !
How could this happen ? Why aren't the esters 1.5 times higher too ?
Perhaps because (for reasons unknown) the FA synthesis chain is
operating at only 67% of normal at the higher temp or perhaps the AAT
cleanup is only 67% as effective at the higher temp.
Certainly possible.
>>>>Also, there is the question of what Boulton and Quain mean by
>>>>"oxygen maintained at a constant value." Do they mean initial
>>>>oxygen concentration? Or constant aeration at some level--leading
>>>>possibly to respiration by the yeast?
It's almost certainly initial oxygen, and they would certainly not be
talking about respiratory levels of O2 in the context of brewery
fermentation control, but I'm asking for a reference citation.
>>>>I think somebody should contact them--I'll do it if necessary.
I'm planning this after I re-read the section leading to their
statement and try to correlate this with their (Bass Brewery) patented
pitching method.
-SteveA
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Date: Thu, 17 Nov 2005 20:00:37 -0600
From: "Sean Richens" <srichens at mts.net>
Subject: Re: Need advice -- All-grain system
May I chip in my stovetop brewery? Quite down to basics.
http://hbd.org/discus/messages/366/30412.html?1116901187
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End of HOMEBREW Digest #4891, 11/17/05
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