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HOMEBREW Digest #4624
HOMEBREW Digest #4624 Sun 10 October 2004
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
Atteunation, yeast vs wort (was Re: Cider and "low attenuation" yeast) ("Fredrik")
Re: Cider and "low attenuation" yeast ("-S")
Re: low-attenuating yeast (Fred Johnson)
Info needed on Brewpubs in New York State (marty)
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Date: Sat, 9 Oct 2004 09:43:33 +0200
From: "Fredrik" <carlsbergerensis at hotmail.com>
Subject: Atteunation, yeast vs wort (was Re: Cider and "low attenuation" yeast)
Whoa, n'th post-attempt after cutting lines n-1 times,
sending this to the wrong address etc! This is driving me nuts :o)
Hope the short lines doesn't make this unreadable.
> Date: Thu, 7 Oct 2004 07:26:57 -0400
> From: Fred Johnson <FLJohnson at portbridge.com>
> Subject: Re: Cider and "low attenuation" yeast
Fred Johnsson wrote that atteunation *mainly* (not only)
depends on the wort, and that the attenuation ranges posted
by the yeast manufacturers apply to some undefined
standardworts, fermented using some standard pitching rates,
and under otherwise standard conditions. I agree completeley
with this.
Since this came up I thought I could post some of my thoughts
on this subject, showing some ballpark estiamtes I have been
using until I've got a full model running.
Certainly the exact attenuation depends on the full set of
variables, ranging from yeast, wort and fermentor and ambient
variables. But for practical purposes, in order to at least be able
to do a little bit better ballpark estimates than the standard
attenuation ranges posted on the yeast manufacturers page
I have decomposed the problem into two parts.
Assumptions used in this ballpark estimate
1. The most relevant ferementables in beer wort are glucose,
fructose, sucrose, maltose and maltotriose.
2. Under at least "reasonable conditions, picthing rates" most
strains(there might be some exceptions) fully deplete
everything except maltotriose.
Definitions.
I have attempted to parametrise the wort sugars by ...
RDFW = Real Degree of Fermentabilit of Wort (=glucose+
fructose+sucrose+maltose; % of extract)
MTW = MaltoTriose contents of Wort (% of extract)
RDF = Real Defree of Fermentability (in actual fermentation)
MTD = MaltoTrioseDepletion (% of maltotriose depleted)
This in this simplified variable set one would arrive at this
relation
RDF = RDFW - (1-MTD)*MTW
Thus the upper limit of fermentability is totally determined by
the wort (RDFW). There is no hard lower limit but for
"most strains" and for "reasonable" conditions I would assume
that the lower limit is approximately RDFW - MTW.
What remains is to estimate MTD and MTW.
If you are using DME hopefully there are datasheets. I think
muntons light DME has something like
MTW = 10.4% (could be a little lower maybe)
RDFW = 65%
I am still working on getting control over my mashing. But
eventuelly I belive that MTW as well a RDFW could be at
least roughly estimated from the mash scheduele, by means
of modelling the mash. I started this project but has had
time to work on it as much as I'd hoped. But evenetully I
figure it will fall into place. I think the hard parts is not
enzyme modelling, the hardest parts seems to be modelling
the liquification of grains and starch, but I am still working
on it. Until then I rely on basic empricial formulas. Fix
suggests some simple relations between MTW and RDFW
if you are using a fixed scheduele. Otherwise I figure you
can do some attenuation testing using low and high strains
to pinpoint roughly the wort parameters.
I have transformed this into another rough formula directly
involving FG. There may be some minor errors in thte
constants from the fitting, since it depends on alot of things.
FG = (a*OG + b) ( RDFW - MTW*(1-MTD))
+ (c*OG +d)
a = -1,180875689
b = 1,179398127
c = 0,993948859
d = 0,006096669
To estimate the MTD. I have made an assumption of this
"standar wort" they must be using, And translated their
apparent attenuation ranges into MTD ranges. It's
admittedly a bit foggy, but I figured it's the best you can
do at the moment and better than nothing. Until there is
a better model. I emailed wyest on this standard wort
issue, but they didn't respond. My wild assumption is
that the standard is something like 1.040-1.045,
RDFW=64-65%, MTW = 10.5%, pitching rate =
1 million/ml/P and otherwise normal fermentation. Eventually
I hopeto be able to find a better estimate for MTD that also
includes some starvation and ethanol inhibiation issues
and pitching rate. For example if you fermented cider I
assume MTW would be practically 0% and all strains should
have pretty similar and full attenuation, unless it runs out of
some other nutritons. That is the next step to find out.
I am still tuning the fermentation model. Right now I am
trying to invent some conditions to regulate transition from
active to dormancy. I am working on energy stress model,
where I translate all stress factors into energy equivalents,
and the idea is that at the point where the stress factors
are more costly than the energy production do to hard
digestible or low concentration of sugars, the cells will go
dormant. So I think of stress as a king of energy
thief/leakage. The the accumulated weigthed stress is
what I will try to trig on. So far I think the idea looks promising.
One objection to this is that estimates MTD and MTW
aren't easy. But I think it can be done good enough, to
allow far better FG estimates that the figures put on the
yeast companies webpage that seem based on undefined
standards.
I have only brewed for 1.5 years so I do not have alot of
experience, but so far I have found my estimates using this
accurate enough, within the measurement errors. I have made
some receips from scratch, and the only times I have had
major deviations from my estimates is when have done AG.
The problems is that I yet do not have a reproducable
procedure that I can model.
/Fredrik
------------------------------
Date: Sun, 10 Oct 2004 00:32:36 -0400
From: "-S" <-s at adelphia.net>
Subject: Re: Cider and "low attenuation" yeast
On low attenuating yeast, Fred Johnson wrote ....
>Certainly
>this is a reasonable question considering that the yeast companies
>describe their yeasts in terms of their level of attenuation, and one
>would assume that the figures for attenuation for the yeast are tell
>you what the yeast will do. Such was also my assumption until I
>repeated discovered that the figures often don't really apply.
[...]
I agree with Fred's comments. Not only do brewing yeast companies but also
yeast banks like NCYC characterize yeasts on the degree and rate of
attenuation, *BUT* those figures only have meaning when the media(wort),
the yeast handling and the growth conditions are standardized. Common
brewing results could be entirely different.
One thing that is very puzzling wrt attenuation is that different yeasts do
'give up' sooner than others, yet we can say with confidence that all
brewing yeasts ferment all major fermentable wort sugars - Maltose, Glucose,
maltotriose and residual sucrose, to some extent. Let's put some numbers to
this.
Some typical 12P(1.048) wort may achieve a 75% attenuation under forced
fermentation conditions. 75% attenuation requires the conversion of about
61% of the extract into ethanol or fermentation of 7.3 Plato of sugar.
[Yes, only ~60% of extract is fermentable in a typical wort !]
In similar worts the mass breakdown of fermentables is roughly:
62% maltose
19% maltotriose
13.5% glucose
5.5% sucrose (actually 90% sucrose w/ minor amounts of others)
As the wort attenuates and gravity readings drop from 1.048 to 1.012, the 36
gravity degree change is nearly proportional to the fermentable sugar mass
converted to ethanol. So of the 36 degrees lost, about 62% of that is
attributable to maltose fermentation and so on. This gives the attenuation
contribution as:
22.3 grav.degree, maltose
6.8 grav.degree, maltotriose
4.9 grav.degree, glucose
2.0 grav.degree, sucrose et al
We know from studies that most (certainly not all) healthy brewing yeasts
will completely ferment out glucose, sucrose, maltose in wort and that the
amount of maltotriose unfermented is among the more variable portion of what
is fermented. This means that 29.2 degrees of attenuation(81% of expected
attenuation) is 'given' in any reasonable fermentation of this wort. We
fully expect that the 1.048 wort must drop to 1.018.8 for nearly any
reasonable yeast. The question is how much of the remaining 6.8 degrees of
maltotriose attenuation materialize.
Looking down Wyeast's lists of apparent attenuation ranges expected from
various yeasts we see values given a += 2 or 3% attenuation range.
Considering the center point of this range and ignoring the high and low
extreme yeasts we find that typical results for low attenuating yeasts give
around 69% attenuation and high attenuating ones about 75% under Wyeasts
conditions. This means a low attenuating yeast must typically consume 92%
of the extract as a high attenuating ones. The 8% delta corresponds to low
attenuatnig yeast capable of fermenting all the maltose, glucose, sucrose
and about HALF of the maltotriose in quantity.
A few rare yeasts may turn up their noses at sucrose or fail to finish the
maltose or whatever but it's a fair generality to say that the difference
between high and low attenuating yeasts is how they handle the LAST HALF of
the maltotriose. Here's the puzzle - why do low attenuating yeast stop
fermenting when there is still plenty of food on the table ? Obviously
these yeasts have the metabolic mechanisms to consume maltotriose - so why
not finish the meal ?
More questions than answers this time,
-Steve
------------------------------
Date: Sun, 10 Oct 2004 06:10:11 -0400
From: Fred Johnson <FLJohnson at portbridge.com>
Subject: Re: low-attenuating yeast
Many thanks to Steve Alexander for his thoughts and comments on
differences between low- and high-attenuating yeasts. After careful
consideration of the various sugars and their proportions in wort,
Steve poses the reasonable question (paraphrasing), "So why do these
different yeasts leave behind different amounts of maltotriose?"
This makes me wonder, "Are all maltotrioses the same? And is there room
here for some subclassification of these sugars, in which case a
particular yeast can transport and metabolize certain maltotrioses but
not other maltotrioses? Or perhaps there is a difference between yeasts
in the kinetics in the uptake or metabolism of maltotriose (and for
other sugars also), such that the transporter(s) on some yeast strains
simply do not transport appreciably when the concentrations of the
substrate gets below a certain level.
Perhaps we should pose this and related questions to the yeast experts
in the Fortnight of Yeast, 2004. I'll start this ball rolling and post
a question to Drs. Fischborn and Waldrop tomorrow.
Fred L Johnson
Apex, North Carolina, USA
------------------------------
Date: Sun, 10 Oct 2004 14:04:10 -0400
From: marty <bigbrewdude at optonline.net>
Subject: Info needed on Brewpubs in New York State
Hello all,
I'm new to the HBD, so I don't know if this has been discussed already...
One of my buddies is buying a pub and he asked be to get all the information
I could about what hoops the government want brewpub owners to jump through.
Any ideas who to contact? Any help would be appreciated.
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End of HOMEBREW Digest #4624, 10/10/04
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