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HOMEBREW Digest #4848
HOMEBREW Digest #4848 Thu 15 September 2005
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
Re: esters, acids, and practical ideas for fermenting beer ("-S")
Binchoise ("Dave Burley")
Binchoise Blonde ("Dave Burley")
hops (yawn..) and sleepiness (snore) (bob.devine)
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Date: Thu, 15 Sep 2005 04:14:56 -0400
From: "-S" <-s at adelphia.net>
Subject: Re: esters, acids, and practical ideas for fermenting beer
Matt says,
> Anyway, I understand very well that in cases where some growth factor
> other than sugar causes yeast growth to slow, we get a big spike in
> ester production. I am tempted to call this a "stuck ferment ester
> spike," and then ignore it because even when I want lots of esters I
> plan to avoid sticking my ferments.
It's not just a stuck fermentation spike. The yeast cells in our
fermenters are in various states as fermentation comes to a close.
Normally a "race" as to whether oxygen product, amino-acids or sugars will
be the critical limit to growth. Many "normal" fements slow or even dawdle
near the finish line yet attenuate well enough. Here part of the yeast
population lacks growth conditions ! Perhaps sufficient O2 product
(sterols and UFAs) are missing. Perhaps the amino synthesis capability of
part of the yeast population is inadequate to induce maltotriose. Certainly
some cells have less capable membranes than others and will halt earlier for
energetic reasons.
A stuck fermentation occurs when essentially all cells are growth inhibited
(and produces a clear spike of esters). That's an abnormal case. In a
dwindling fermentation some part of the yeast population has growth
limitation and this fraction will produce the excess esters we are talking
about.
If your fermentation finishes powerfully and you only observe flocculation
very near final attenuation, then you've probably minimized these "growth
cessation" esters. BTW yeast only flocculate after they have ceased to
grow, so the extent of flocculation is a very good indication of the
growth-cessation condition.
> BUT... maybe I'm going too far,
> because maybe an ester spike happens even in healthy, sugar-limited
> ferments as well.
I suspect so, though probably smaller in magnitude as the acetylCoA supply
dwindles.
> This was really why I
> asked whether there are still pools of Acetyl-CoA available after
> growth stops--but I forgot to specify that I am most interested in the
> case where growth stops *because the sugar runs out*. Any thoughts on
> that?
The three primary sources of acetylCoA in brewery yeast are the sugar
catabolism path, the amino catabolism path and the fat beta-oxidation path.
You have stated the sugar is gone, and normal beer has low amino levels.
Beta-oxidation: yeast have the capacity for beta-oxidation, but it probably
only occurs in essentially "starvation conditions". There are very few
practical brewing studies on beta-oxidation in yeast. My hunch is that
yeast in the bottom of your fementer, even a week after attenuation, are
living in a low energy dormant state and fermenting the low concentrations
of fermentables left, not burning fat. They are producing minimal levels of
acetaldehyde which is primarily being converted to ethanol.
In a previous post I mentioned that AAT is probably not available equally
throughout fermentation, but may spike as growth ceases. I also would
suspect that it's level falls off rapidly as cells flocculate. I wouldn't
expect the flocculated yeast cake to become significant ester producers
> An
> acetaldehyde molecule has one less oxygen than an acetic acid molecule.
> Where does the oxygen come from to make this reaction happen?
Most texts just point to the pyruvate and the pyruvate dehydrogenase which
together with a CoASH directly produce acetylCoA (actually it's a 3 enzyme,
3 step process). We know that doesn't happen in anaerobic yeast based on
recent studies, the enzyme is absent. It appears that all the acetylCoA
comes from pyruate -> acetaldehyde -> acetate (the acetic acid anion) ->
acetylCoA, but most books supply few details.
The first step is the same as the direct mechanism, applying pyruvate
decarboxylase(EC4.1.1.1) in removing the carboxyl group of pyruvate which
yields acetaldehyde. The next step applies an aldehyde dehydrogenase to the
acetaldehyde. There are "aceylating aldehyde dehydrogenase" enzymes
(EC1.2.1.10) which can produce acetylCoA directly from CoASH and
aetaldehyde, but these don't occur in yeast. Instead yeast apply an
EC1.2.1.3(or EC1.2.1.4, EC1.2.1.5) aldehyde dehydrogenase enzyme to the
acetaldehyde and produce the acetic ion plus a little energy. The
difference in these three classes of enzymes are whether the energy
collection is via NAD+, NAD(P)+ or NADP+ - I don't know or greatly care
which. Here is the reactions:
acetaldehyde + NAD+ + H2O = acetic acid + NADH + H+
*** Note that the oxygen comes from water.***
Note also that this is different that the aerobic oxidation by acetic acid
bacteria aerobic yeast which use free O2.
> A Practical Idea:
> Let's say, first of all, that we pitch an adequate amount of healthy
> yeast into a sufficiently nutritious/aerated wort, so that the yeast
> are still happy and healthy when the sugar runs out. Let's also say
> that we want to minimize diacetyl and fusel levels. Finally let's say
> that we can easily raise the ferment temp to at least the low 70s
> whenever we want, just by leaving our carboy at room temperature and
> letting the yeast do its thing. How do we use the ferment temp to
> control esters?
All of the causative factors (except he enzymes) interact, so you can't
purely increase esters and also minimize fusels for example. It makes little
sense to warm the ferment early when there is little alcohol, maybe little
AAT, and plenty of growth to little free aceetylCoA, so warm the fermenter
as the fementation declines. Also fermentation releases considerable heat
and so insulating a fermenter will increase the temp connsiderably above
ambient. Unfortunately the fusels are likely to be produced at the end as
the amino acids dwindle. The warm active finish should pose no diacetyl
problem
I think a simpler approach to increasing esters is to reduce the pitching
rate and oxygenation so the fermentation slows at the finish. Also
modestly elevating the late fermentation final temps.
>...
FWIW Kunze discusses weizen beers which are highly estery ales and top
sellers in Southern Germany. For these he starts with 11-12P wort, he
pitches 0.3L to 1L of [slurry] per 100L {low to high pitching rate}, at
12C(54F) and allows the fermentation temp to rise to 13C-21C(56F-70F) over
the 4 day fermentation. So yes he pitches cool and allows the temp to rise,
perhaps considerably.
> Ringwood yeast seems like another possible application.
You'll never control the diactyl with that yeast !!!
-S
------------------------------
Date: Thu, 15 Sep 2005 10:01:01 -0400
From: "Dave Burley" <Dave_Burley at charter.net>
Subject: Binchoise
Brewsters,
Chad Stevens asks about the flavor components in Binchoise' Brew.
BINCHOISE BRUNE
from Brasserie Binchoise is a complex artisanal Wallonian brown ale. It is
flavored with aromatic hops, star anise and orange peel. It has dark brown
color with reddish highlights, hoppy bite and aromatic spice character; rich
and warming.
Keep on Brewin'
Dave Burley
------------------------------
Date: Thu, 15 Sep 2005 10:30:48 -0400
From: "Dave Burley" <Dave_Burley at charter.net>
Subject: Binchoise Blonde
Brewsters:
Here is some more info on Binchoise brews Chad asked about:
BINCHOISE BLONDE
from Brasserie Binchoise is a complex artisanal Wallonian blond ale. It is
flavored with aromatic hops, coriander and a touch of Curacao. Has honey in
the bouquet and peppery, dry, very appetizing finish. It has 6.5% alcohol
ABV
Binchoise Brune has an ABV of 8.2%
Keep on Brewin'
Dave Burley
------------------------------
Date: Thu, 15 Sep 2005 17:25:38 +0000
From: bob.devine at att.net
Subject: hops (yawn..) and sleepiness (snore)
Jeff asked about some semi-rigorous connection
between hops and sleepiness.
Here are some that *sound* authoritative
http://www.hort.purdue.edu/newcrop/duke_energy/Humulus_lupulus.html
http://herbalgram.org/bodywise/expandedcommissione/he047.asp
http://www.hbcprotocols.com/sleep/hops.html
http://hops.sleeplibrary.org/
Many articles repeat the hops == soporific without
providing a source. But here is a good source:
http://www.uic.edu/pharmacy/research/diet/content/
scont_womens_health_hops_hlrefs.htm
[Article in German] Abstract: Hops are told to promote sleep; manyfold
efforts to detect the soporific principle have been unsuccessful so far.
Preliminary pharmacological tests lead to the conclusion that the
soporific activity of the exhalation of hops [essential oil] can be
explained by its content of 2-methyl-3-butene-2-ol (1) in the volatile
fraction. It was found that (1), when given to mices i.p. (800mg/kg)
produces narcosis for about 8 h.; no abnormail behaviour was observed
there upon. Due to its water-solubility the concentration of (1) in the
essential oil obtained by steam distillation is low; contrary to that,
(1), is enriched in the more volatile fraction of hops.
Yeah, "mices" and "abnormail".
This might be the referenced study
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?
cmd=Retrieve&db=PubMed&list_uids=9757514&dopt=Citation
But the above study used a combination of hops + valerian.
They conclude:
"This study shows that the investigated hop-valerian preparation in the
appropriate dose is a sensible alternative to benzodiazepine for the
treatment of nonchronic and non-psychiatric sleep disorders."
Bob Devine
Riverton, Utah
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End of HOMEBREW Digest #4848, 09/15/05
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