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	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
  Alexandre's  Rocket Fuel and Fusels ("Rob Moline")
  Vigorous Secondary ("Alexandre Enkerli")
  RE: Bubble Gum Smell[SEC=UNCLASSIFIED] ("Williams, Rowan")
  bubble gum (leavitdg)
  RE: Bubble Gum Smell ("David Houseman")
  bubblegum ("Gordon Strong")
  Re: Rocket Fuel and Fusels (Matt)
  Beer Tools Pro for Linux (Eric Schoville)
  Corny keg post threads ("Dieterle, Jeff R.")
  Thermodynamics of Esterifiction ("Fredrik")
  Candidate compounds for mellowing ("Fredrik")


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Date: Mon, 23 Oct 2006 23:51:16 -0500
From: "Rob Moline" <jethrogump at mchsi.com>
Subject: Alexandre's  Rocket Fuel and Fusels

			Rocket Fuel and Fusels
Alexandre,
     The fusels are a by product of fermentation, produced in proportion to
the gravity. Higher OG's have higher everything, including fusels....But
your time viewpoint is spot on, a high gravity brew some might, and I have,
considered to be worthy of the drain, become wonderful with a prescription
of "Tincture of Time."
     Consider the progression of gravities in ETOH products, and the time
they are commonly aged...barleywines, 6-12 months.... wine, years....
whiskey, decades.
     I used to envy the angels for their share, till I realized all they got
were fusels!
Cheers,
Jethro Gump
"The More I Know About Beer, The More I Realize I Need To Know More About
Beer!"



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Date: Tue, 24 Oct 2006 01:08:57 -0400
From: "Alexandre Enkerli" <enkerli at gmail.com>
Subject: Vigorous Secondary

Matt asks about the vigor of a secondary fermentation.

> I recently observed a strange phenomenon.  A saison I brewed finished
> primary fermentation pretty fast; the airlock bubbling decreased
> dramatically over a period of a few hours on the second day of
> fermentation.  As expected, the secondary ferment got slower and slower
> over the next few days--but then instead of tapering off to nothing it
> increased noticably to a steady level of one bubble every few seconds,
> and stayed steady for 2 days.  This is where I'm at now.  There is
> quite a bit of settled yeast, but also a whole lot of yeast still in
> suspension.
Sounds interesting. Is it that unusual? I seem to remember many cases like that.
So, my own questions...

What yeast did you use (Wyeast and White Labs have very different
Saison strains)? Did you rack the beer into a secondary fermenter or
did you take yeast out of the primary (say, in a conical)? What was
the SG at the end of primary? Is it at all possible that another
change happened during secondary fermentation (say, a change in
atmospheric pressure)? Do we know that bubble rates are a good
indicator of fermentation vigor? Is it possible that rousing the yeast
takes a while to have an effect on fermentation?

Cheers!
- -- 
Alexandre (aka Ale-X) in Montreal
http://enkerli.wordpress.com/


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Date: Tue, 24 Oct 2006 15:35:57 +1000
From: "Williams, Rowan" <Rowan.Williams at ag.gov.au>
Subject: RE: Bubble Gum Smell[SEC=UNCLASSIFIED]

Joe asked:
>>
Hello Fellow HBD types;

I have a short but sweet question for all of the BJCP certified judges.

I brewed a Helles using Munich Lager Yeast.  It was cold pitched (1/2 gallon
starter) and fermented at 48 degrees.  It has a distinct bubble gum nose.
Kind of like Bazooka bubble gum.  What produces this aroma?  Is it DMS?
Diacetel (sp)? Or something else?

Thanks in advance for your help.
<<

Now I'm no BJCP judge, but from what I've read, you may wish to cast a
suspicious eye over your fermentation process. The estery bubblegum aroma
may have been caused by low fermentation temps.  48 degrees (9 Celsius in
our metrics) is pretty low (but certainly not out of bounds for Munich Lager
yeast).  Is there any chance that the actual fermentation temp of the wort
versus the surrounding air temps may have dropped any lower during primary
fermentation?

How fresh was the yeast in the modestly sized starter?

Cheers,
Rowan Williams 
Canberra Brewers Club, Australia

[9588.6, 261.5] AR (statute miles)
 


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Date: Tue, 24 Oct 2006 07:06:12 -0400
From: leavitdg at plattsburgh.edu
Subject: bubble gum

I am not certain, but know that with the lagers that I have made it is often/
usually the case that there are lots of odd smells and flavors that age out
with time and cold conditionning...

Let us know on HbD if this is the case with yours...and lets see what others
say.

Darrell



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Date: Tue, 24 Oct 2006 07:21:02 -0400
From: "David Houseman" <david.houseman at verizon.net>
Subject: RE: Bubble Gum Smell

Joe,

IMHO "bubble gum" is a fruity ester most often associated with some Weizens.
Esters are yeast byproducts usually from warmer fermentations and ale yeast
strains.  But ester production is also affected by yeast health, wort
nutrients and aeration, and fermenter geometry.   I have not had bubble gum
aromas but often do have sulfur aromas when using Munich Lager yeast; this
dissipates during lagering.   Are you perhaps confusing a typical sulfur
character with bubble gum?  I haven't had Bazooka Gum in years but I don't
remember it as particularly sulfury.

David Houseman




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Date: Tue, 24 Oct 2006 08:53:44 -0400
From: "Gordon Strong" <strongg at speakeasy.net>
Subject: bubblegum

> I brewed a Helles using Munich Lager Yeast.  It was cold pitched (1/2 
> gallon
> starter) and fermented at 48 degrees.  It has a distinct bubble gum nose.
> Kind of like Bazooka bubble gum.  What produces this aroma?  Is it DMS?
> Diacetel (sp)? Or something else?

I usually get a bubblegum perception in warm-fermented hefeweizens.  I think 
it's a combination of banana and another fruity ester (strawberry, perhaps). 
It's not diacetyl (butter, butterscotch) or DMS (vegetal, sulfury).

I haven't used the Munich lager yeast, so I'm not sure of its fermentation 
characteristics.  However, if you're getting bubblegum, I think you could 
look at issues that increase ester production.  Given that you're fermenting 
cool and using a large starter, you've already addressed two of the main 
causes.  Esters tend to be produced when yeast is either driven hard, is 
overly stressed, or is not fully following main fermentation metabolic 
pathways.

Try to understand the expected profile of the yeast first, and then look to 
sources of increased ester production based on your method and the 
parameters and one-off issues of your specific batch.

Gordon 



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Date: Tue, 24 Oct 2006 07:28:58 -0700 (PDT)
From: Matt <baumssl27 at yahoo.com>
Subject: Re: Rocket Fuel and Fusels

Fusels and esters can definitely be confusing (especially when you
think about how to actually control them).  Alexandre asks for some
clarification.

"Ok, this may be silly but after all this talk about fusels, I'd feel
sillier not to ask.  What gives some of our high-alcohol beverages
(mead especially) its "rocket fuel" taste, if it's not fusel alcohols?"

I think most who have posted lately on this would agree that a harsh
rocket fuel taste CAN come from fusel alcohols (and for that matter I
think ethanol itself can be harsh in high-alcohol and low-taste drinks
like applewine or fermented sugar water).  Most (but maybe not all)
also believe a taste fitting that description can readily come from the
ester ethyl acetate.

"And if it is fusel alcohols, how come they can age out? Or is the
issue that they do age out but that aging takes a lot of time?"

Steve reviewed some mechanisms by which fusels might age out, and it
seemed like one should NOT expect them to age out in significant
quantities.  This is supported by the experience of several people.

However, there remains the question of what, exactly, happens to make
harsh young meads and high-alcohol beers taste better after they have
aged a while.  A satisfactory answer has not appeared.  I still think
it's a breakdown of ethyl acetate, but have zero to back that up.

- ---

It would help to have commercial examples of beers laden with ethyl
acetate or fusels.  A.J. De Lange (I think) once suggested Tetleys for
ethyl acetate.  Steve Alexander has suggested Bigfoot on occasion for
fusels.  I am not well-trained enough in taste to say for sure, but the
hot note I get in Piraat seems to me to be ethyl acetate--can any BJCP
type corroborate this?

Matt



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Date: Tue, 24 Oct 2006 09:38:32 -0500
From: Eric Schoville <eric at schoville.com>
Subject: Beer Tools Pro for Linux

Beertools.com has recently released Beer Tools Pro, which looks
promising.  Unfortunately they only support Windows and Mac, but they
would start a Linux beta if they can get 100 people to sign up.  I'm
posting this in the hope that a couple of people in this forum might be
interested enough to sign up for a beta.  Please see:

http://www.beertools.com/forum/viewtopic.php?p=9684

No affiliation, blah blah blah.  I'm just interested in having support
for Linux.

Thanks!

Eric Schoville
Madison, Wisconsin

http://www.schoville.com/brewing.php



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Date: Tue, 24 Oct 2006 15:41:57 -0400
From: "Dieterle, Jeff R." <Jeff.Dieterle at alcoa.com>
Subject: Corny keg post threads

I'm building a cip line/faucet cleaner for my 3 tap kegerator using a
pump & immersion heater. I'll need to make a couple nipples to match the
male threads on a corny keg post. Does anyone know what the thread
pitch/diameter is ?
 



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Date: Tue, 24 Oct 2006 23:22:57 +0200
From: "Fredrik" <carlsbergerensis at hotmail.com>
Subject: Thermodynamics of Esterifiction

(After several resends...##%&"*!)
- ----------------------------
Relating to the ester and fuesel discussions and an off line discussion
I thought I'd post some further technical general thoughts on the
esterification process to feed the discussion.

Perhaps some painful and lenghty thermodynamical background posts might
have been called for here, but instead I try to be more brief and go right
to the points.

I would really had wanted to provide more numbers, but the reason
is that the thermodynamical tables I have isn't very complete.

The basic focus in this posts is wether esterification can energetically
continute post-fermentation or not, and in either case - Why.

During active fermentation and possibly also during bottle priming,
yeast has pathways to make esters via acyl-CoA

acyl-CoA + alcohol --> ester + CoASH

this takes place inside yeast cells and easily produces beer
esters levels beyond what would be energetically favourable(!) in
the simple esterification process in operation *post-fermentation*:

(*) acid + alchol <--> ester + water

(To a certain extent this is enzymatically supported even during
 fermentation by yeast esterases )

This(*) is the process I elaborate here.

Each of the components are assigned "activities" or concentrations,
and we defined the stochiometric activity quotient Qo

Qo = [ester][water]/([acid][alcohol])

Technically the acid concentration refers to the non-protolysed
acid. But to arrive at something more practical we can instead
define [acid.tot] = [non-protolyzed acid] + [protolysed acid]

Q = [ester][water]/([acid.tot][alcohol])

This is more practical, however the downside is that now we
get a pH dependence in Q (see below).

The unit of [water] is taken relative to pure liquid water.
All the other activities are take in M (mole/liter)

At equilibrium Q = Keq.

The equilibrium value is related to the free energy
change of the reaction via.

DG = RTln(Q/Keq)

One usually defines a standard free energy change DG0.
DG0 = - RTln(Keq), which refers to Q = 1.

For ethyl acetate we have DG0 ~ +4.2 kJ/mol, Keq = 0.16
(This is a value I have calculated from tabulated values in CRC
handbok, SI chemical data and some vapour pressure and solubiliy
considerations.)

Different alcohols and acids give different energies of course,
but to narrow things down, for the esterification processes in beer
a wild guess is that we may see variations like

DG at beer pH at 25 C ~ 0 to +10 kJ/mol which means
Keq ~ 0.01 .. 1

Like I mentioned, I do not have good tables! So if someone with
better tables can find the exact data for more of the expected
esterification process in beer I would be interested to see it.
I think we can have fun with it.

To convert the value to another temperature and pH:

Keq2 ~ Keq1 * [1+10^(pH1-Pka)]/[1+10^(pH2-Pka)] * exp (-DH/R*(1/T2-1/T1))

DH is the enthalpy change of the reaction
pKa the strenght of the acid participating in the esterification.

After some straightforward formula manipulations we get the
esterification rate V := d[Ester]/dt can be written as

V = A*e^(-Ea/RT)*[1 - Q/Keq]

Ea is the activation energy of the esterification reaction. It is
usually *the order* of +50 kj/mol. Which basically means that
the rate of reaction 2-folds for each 10C increase. But the value
would vary from reaction to reaction. One expectation is that
the higher the molecular mass of the ester is, the lower is the
activation energy for hydrolysis, since such molecules while
having the same average energy at a given temperature, they have
a larger typical momentum (implies higher intermolecular forces
during collisions) that is more likely the key. A is a constant of
reaction. Thus one might expect that high molecular size matters
alot to the half life.

Also, in the case of ethyl esters, or any other case where the
alcohol is abundant enough to be marginally changed as the esterification
equilibrium proceeds, we can assume that alcohol concentration to be
constant, and it allows for an analytical solution of the time equations.

[Ester] = [Ester.eq] +
([Ester.0]-[Ester.eq])*exp(-(k2[Water]-k1[Alcohol])*t)

Where [Ester.eq] = -a/2-(a^2/4-b)^0.5

a = -([Acid.tot.0]+2*[Ester.0]+[Alcohol.0]+[Water]/Keq.eff)
b = ([Acid.tot.0]+[Ester.0])*([Alchol.0]+[Ester.0])

( Acid.eq = Acid.0 - (Ester.eq-Ester.0)
  Alcohol.eq = Alcohol - (Ester.eq-Ester.0) )

The interesting part here is to acknowledge that this reaction has an
identifiable half life. And it is the deviation, or concentration gradient
from equilibrium that halves. This may be a useful tool when analysing
rates.

t_half = ln2/(k2([Water]-[Alcohol]*Keq))

More specifically it implies that flavours very excessively
"off equilibrium" beer, would be more unstable than a flavour
near equilibrium.

Example of calculation equilibrium shifts as per the above formulas:
Assume that we have initial levels

[Acetate.tot.0] = 0,0012 M ~ ~72 ppm
[Ethanol.0] = 1 M
[Ethylacetate.0] = 0,0006 M ~ 53 ppm

=> at equilibrium  (IF reached)

[Acetate.tot.0] = 0,00153 M ~ ~92 ppm
[Ethylacetate.0] = 0,00027 M ~ 23 ppm

Interestingly the equilibrium for ethylacetate is in the ballpark
of it's commonly quoted flavor threshold.

When you look at papers of ester aging, you can see that the relative
change of esters varies from ester to ester. I think the distance from
equilibrium may prove to be a key issue.

Now to the point.

We are going to see how much esters we can support at equilibrium
in order to evaluate wether they are likely to increase or decrease
during aging. So we will make estimates at the edges that favor esters.

Some ballpark estimates.

Typical individual alcohol levels (ethanol excluded) are maybe 100 ppm
or a few hundred ppm
( Some of the most abundant: isoamylalcohol, amylalcohol, iso-butanol,
  x-propanol, phenylethanol )

Typical individual fuesel levels are maybe some 100 ppm or a few hundred
ppm too
( Some of the most abundant: acetate, succinate, pyruvate, lactate when
  using in the mash)

Now, Keq < 1 at beer pH.

Let's be aggresive and assume all the above fuesels are at
500 ppm and the acids are at 300 ppm.

Our energetic considerations now gives us that
[Ester.eq] ~< [acid.tot][alcohol] * 1/M
[Ester.eq] ~< 0.005 * 0.006 = 0.000035 M < 3 ppm

Now the conclusion seems clear. The equilibrium is such that
the ester levels are a couple of orders of magnitude below that of the
alcohols - meaning that the esterifications or hydrolysis can not
by any reasonable logic make a significant impact on flavour
intensities of the alcohols.

If anything I think aging are generally more likely to reduce ester
levels, except of course that it is painfully SLOW.

So to answer the original question, does esters keep form during aging?

1) First it seems in most cases that this is not so simply because,
regardless of the time factor, it's simply not favourable from a
thermodynamic point of view.

2) Second, with some exceptions(beeing "odd" esters with an extremely
low flavour treshold, that is below it's equilibrium values) any
flavours changes taking place (in either direction) (against the odds of
the time factors) are likely to matter mainly to the relative ester
flavour intensities, not the fuesel intensities.

About the rate tweaking I see three factors.

1. How far from equilibrium are we? The more extreme, the higher is the
   rate  to bring us closer to equilibrium.

2. Temperature. As can be seen above temperature matters. (pH may matter,
but
I figure the variation in pH from beer1 to beer2 isn't that big.)

3. Possible activity of esterases leaked from yeast. This would
   certainly speed the approach to equilibrium. I am not sure how big
   impact this has though.

I'm not sure if my "point" come up readable.

 /Fredrik



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Date: Tue, 24 Oct 2006 23:26:59 +0200
From: "Fredrik" <carlsbergerensis at hotmail.com>
Subject: Candidate compounds for mellowing

FWIW, some more wild speculations...

I have not experienced much of the so called rocket fuel beer going
good myself so I have limited first hand experience. But I've learnt
to not always take flavor descriptiors litteraly as I wrote in my
previouos post. I remember my first beer, high on ethyl acetate and
funky iso-butanol notes, which certainly qualifies as as solvently
fuesel soup. Of course I should have saved this as an aging experiment,
but beeing my first batch that never occured to me at that point so
it went down the toilet.

Just looking at the logic of energy considerations, my guess is that
the most likely post-fermentation aging changes regarding the
ester/fuesel thing would be hydrolysis of ester and a decline in
estery aroma. My argument is that it's the only way I can
find seemingly good logic.

Ontop of that there is the oxidation reactions of course. But I
don't see how that would interfere much with this. It would guess
it's a parallell thing.

Considering the comparatively high ethyl acetate equilibrium point,
relative to it's flavour threshold and the typical balues, I would
expect this specific ester to age more slowly than other esters,
because it's not that awfully far from equilibrium.

Then we have the ethyl esters of the 6-10 chain yeast fatty acids.

ethyl-hexanoate is the supposed apple aroma.

ethyl-decanoate is supposedly whisky/brandy like, so perhaps this is
a candidate? As per the logic in the previous post, I think this
has the potential to drop faster than other esters. Also, this
has a much higher molecular mass than for example ethyl acetate,
meaning that in a blind guess, one might suspect that this ester
is more unstable, further making it a good candidate compound.

To further speculate, what conditions would possibly cause high
levels of this ester? I might suspect that the C6-C10 acyl-CoA
are possibly from flushing the manufacturing acyl-CoA pools when
fatty acid synthesis is downregulated in the end of fermentation,
or from a mistuned coregulation of production vs consumption.
Then these might be esterified as as way to dismiss them into
something less stressful and at the same time recycle the CoASH,
as part of a combined flow control/recycling/detoxification. That
is all good logic to me.

High gravity fermentations could well fiddle with these factors.
The regulation of ATF1/2(acetate esters) are farily studied in
several papers and the impact of oxygen and UFAs are known, but
I have not yet seen the similarly in depth studies of the
EEB1/EHT1 regulations, so Who knows. Unlike the ATF1/2 genes,
these genes doesn't respond to oxygen and UFAs the same way.
Furthermore it's ester products are reported to not be as
expression sensitive. The enzymes also posses esterase activity
 - unlike the ATF1/2p.

I've read this in several articles, here is one.
"The Saccharomyces cerevisiae EHT1 and EEB1 Genes Encode Novel Enzymes with
Medium-chain Fatty Acid Ethyl Ester Synthesis and Hydrolysis Capacity"
http://www.jbc.org/cgi/content/abstract/281/7/4446

Of course the acetate esters could also be players, for that matter,
but it seems then their flavors would be noticable too. There is
also an acetate esterase(IAH1p) enzyme.

I would keep looking for funny esters to explain the mellowing
phenomenon.

Interestingly, in the spirit of the technical framework in my last
post I briefly analysed the data provided in

"Evolution of chemical and sensory properties during aging of top-fermented
beer."
http://class.fst.ohio-state.edu/fst611/Papers/Vanderhaegen%202003.pdf
(a nice paper sent to me in an offline discussion)

and it seems that the apparent "halflives" (as defined
in my lat post)  at  20C ranged from 1 year (ethyl acetate) down to
only 3-4 months! Incidently the most unstable flavours seem to be
the long chain ethyl esters. I admit these are vague estimates but if
we go along, the ethyl decanoate has an apparent half life of around
5 months. In this paper these compounds where not above the threshold,
but then we should keep in mind that this paper investigate a commercial
beer, most probably quite "decent". Extrapolating the numbers to an imagined
homebrew "rocket fuel" i can easily picture these levels rise. Add
ontop of this that perhaps sometimes esterases may significantly
speed things. Unfortunately the paper does not define wether the
beer was filtered or "treated", it just says it's fresh beer from
a belgian brewery.

While it's true that aging are bound to be somewhat slow, to me
it is within reasonable logic that some esters may significanatly
change in flavour intensity during aging. I guess it remains to find
out to what extent esterases are required for reasonable time frames.

If it would be really the case that fuesels in a significant way
age out (which I doubt), then it sure begs the question how that
is energetically possible unless there is any microbial activity?
In respect of our ignorance maybe we shouldn't say never, but at this
point, it seems to me to be unlikely to be the explanation.

 /Fredrik



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