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	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
  Artificial & other sweeteners: an overview (David Radwin)
  Fortnight Of Yeast, 2004 - stress vs biomassyield ("Fredrik")
  Kinetics and Thermodynamics, CCFC in Tazzie ("Dave Burley")
  Re: Pump Mounting ("Martin Brungard")
  Re: Curve Fitting (Christopher Swingley)
  FOY, 2004 -Response- Published attenuation levels for various yeasts- Fred Johnson ("Rob Moline")


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*               A Fortnight Of Yeast                    *
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*      Questions submission: 10/11 - 10/22/2004         *
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* More info http://hbd.org/hbd/archive/4620.html#4620-3 *
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Date: Mon, 11 Oct 2004 19:47:15 -0700 (PDT)
From: David Radwin <dradwin at yahoo.com>
Subject: Artificial & other sweeteners: an overview

Related to some recent discussion, this article might
be useful for anyone considering using Splenda,
stevia, or various other sweeteners for beer or cider.
It's informative but not especially detailed or
technical.

http://tinyurl.com/6p6fe or
http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicl
e/archive/2004/09/15/FDGA58M7L21.DTL

David 


		


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Date: Tue, 12 Oct 2004 06:51:28 +0200
From: "Fredrik" <carlsbergerensis at hotmail.com>
Subject: Fortnight Of Yeast, 2004 - stress vs biomassyield

Dr. Fischborn and Dr.Waldrop, thank you very much for 
hosting another fortnight of yeast! This is like Xmas for us.

First I'm sorry to post so "long" and not very distinct questions 
but if I just made it short there may be misunderstandings, so I 
try to explain some of the motives and elaborate the questions. 
Your and everyone elses comments on these issues are much 
wanted!!

I have some questions regarding yeast that just to set them in 
proper context are related to my attempt to understand yeast 
and make a computer simulation of a beer fermentation. I am 
currently modelling the states, active dormant and dead. And 
the transitions are considered by transition probabilites 
(statistically that is), and the transition functions are suppsoed to 
be state functions of yeast, wort and fermentor variables. The 
below question all relate to stress and biomassyield and to an 
extent the transition probabilites between states. I hope
to decompose the stress into some principal stresses, and find
how the depress the biomass yield (but also how they case 
damage and death, which is another side of it)

Q1 --------------------------------------------------------------
Tracing back to Balling, many formulas in brewing, including 
alcohol/FG/OG formulas tend to assume a fixed biomass yield of 
some 5%. As I understand this is an empirically determined value, 
that I assume is an effective average under "typical conditions". 
But as far as I understand the biomass should be a dynamic 
and in an extended dynamic treatment I doesn't seem valid to 
treat the biomass yield as a constant? Stirplates in starters
are but one example.

Note: I am aware that respiration levels does increase the 
biomass yield too, but that is not what I am after here. I am
trying to understand stress depression of the yield.

Considering the biomass yield vs time, during a batch fermentation. 
Since stresses build up, and especially external sugars drop in the 
very end I am assuming that the biomass yield must drop during 
fermentation. For example, as the sugar concentration is low the 
rate of energy production drops.

Actual Q1) 
    How low is the cellwise biomass yield  at  EOF, just before the 
cells start to tend to go dormant? What do you think about the 
idea that the biomass yield drops to close to zero? What about 
correlating the transition from active to dormant with the biomass 
yield drop? 

The idea I have is that the biomass yield in turn would depend on 
the free energy balance. Incomes - expenses. Expenses also 
including possible stress factors, transport costs etc. 

If you feel this still is a dim question perhaps you can elaborate 
about the topics of dynamic biomass yield and biomass - stress 
correlation?

Q2---------------------------------------------------------------

Actual Q2)
    In a normal batch fermentation, how would you rate these 
different factors that depress the biomass yield?
: CO2, alcohol, concentration gradients on culture, 
UFA/sterol drop

When using a stirplate but *not* aerate, what  factor is most 
important beeing responsible for the increased biomass yield? 

i.e I want to if possible put numbers on how much the CO2 
supersaturation depresses the biomasyield. etc.

Have these things been quantified, and isolated from other stress 
factors? What if you stirr in an pressure gas chamber of high 
CO2 pressure, would the benefit from removal of gradient be 
significant still? Or is it some mechanical excitation of the cells?

Q3 ------------------------------------------------------------
 As alcohol tolerance are supposed to relate to pitching rates, 
sterol levels and also other add-on stress factors, I wonder what 
the conditions are for the alcohol tolerance numbers that you 
sometimes find for strain descriptions? It seems clear that there 
has to be a limit, but it also seems that the limit can be stretched? 
(ie it's not fixed) so the question is thus

Actual Q3) 
    How does yeast companies typically *define* the alcohol 
tolerance limit? ie. what is the exact experimental setup/conditions 
and numerial procedure used to arrive at the alcohol tolerance numbers?
- -----------------------------------------------------------------

 /Fredrik 



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Date: Tue, 12 Oct 2004 10:54:23 -0400
From: "Dave Burley" <Dave_Burley at charter.net>
Subject: Kinetics and Thermodynamics, CCFC in Tazzie

Brewsters:

/Fredrik is postulating that it is an energetic relationship as to why the 
maltotriose is the "last to be consumed".   I doubt that and suspect it is a 
kinetic phenomenon, as are many of the cell wall transport phenomena and 
enzyme reactions.

Perhaps part of the problem is /Fredrik's concept that somehow the yeast take 
in and consume carbohydrates serially. Not so. All the carbs are being 
processed in parallel. Some just more slowly than others.
- --------------------
Stuart Grant is contemplating a CCF chiller to be used to withdraw his hot 
wort to his fermenter and worries if it will work by gravity.

As far as working by gravity mine does just fine with a meter of height 
difference, but you may get some grief with the pelleted hops as I have in the 
past. Even with a Choreboy filter, the finely divided hops in combination with 
a high OG wort can slow down or even stop as it cools.

Surely it is possible even in the Outback of Tazzie to mailorder some leaf 
hops to use as part of your hop charge. These leaf hops will act as a filter 
bed for the pelleted hops. Otherwise, I'd forget the idea based on my 
experience, unless you use  a large diameter inner tube ( I think mine is 1/4 
or 3/8 inch) on your CCF chiller. This will reduce your chilling capacity 
unless you use a longer tube to get the same total inner surface area as the 
smaller inner tube I use.  Then again that cold tap water from near the South 
pole may do the job just fine with a larger diameter inner tube.


Keep on Brewin'

Dave Burley 




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Date: Tue, 12 Oct 2004 07:13:39 -0800
From: "Martin Brungard" <mabrungard at hotmail.com>
Subject: Re: Pump Mounting


Mike O'Donnell posed a question about the mounting of a March mag pump.

I work in the water and wastewater industry and deal with pumps frequently.  
Most motors are designed to work in a particular shaft orientation.  The 
main reason that a motor needs to be oriented as intended is for bearing and 
shaft life.  In the case of a horizontal motor, there is only limited 
provision for axial loading.  Frequently, this is in the form of a couple of 
simple thrust washers.  These washers are subjected to occassional contact 
with the rotor just to keep the rotor centered in the motor casing.  When 
turned vertical, one of the thrust washers is subjected to constant loading 
from the rotor weight that will result in overheating and failure of the 
washer.

In the case of a vertical shaft motor, the bearing system has been designed 
to support the constant axial load from the rotor weight.  Usually, the 
motor is intended for only one vertical orientation, ie the motor can't be 
mounted upside down.  Then the axial load would be placed on the bearing 
that wasn't intended to support an axial load.  Its debatable if some 
vertical shaft motors can be used horizontally, but for the most part, they 
shouldn't be.

I just checked the March website and confirmed that they specifically say 
that their pumps must be mounted horizontally.  I have been into my March 
pump and can attest that they only have simple thrust washers at the shaft 
ends.  They would not perform well in a vertical configuration.


Martin Brungard
Tallahassee, FL




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Date: Tue, 12 Oct 2004 12:23:32 -0800
From: Christopher Swingley <cswingle at iarc.uaf.edu>
Subject: Re: Curve Fitting

Greetings!

* Martin Brungard <mabrungardathotmail.com> [2004-Oct-11 05:12 AKDT] 
* wrote:
> One of the most widely known packages is Excel.  Another is Grapher.  
> Both of these programs are commercial and somewhat expensive.  Curve 
> fitting is not their main purpose.  Neither of these programs do this 
> job very well.

Agreed.

> Fortunately, there is a cheap way to get a better solution.  There is 
> a shareware product called CurveExpert that is specifically intended 
> for curve fitting.  It does a very good job.

Another good, and free choice is the 'R' statistical package.  It is an 
open-source implementation of the 'S' statistical computing language, 
and is available for Linux, Mac System 8.6 - OS X, and Windows 95 or 
later.  It is *certainly* more difficult to use than the program Martin 
mentions, but it is a full featured statistical package so it can do a 
lot more than just curve fitting.

Consult:

    http://www.r-project.org/

for more information, and download locations for your platform.

I've been using the program for the past year in an attempt to predict 
apparent attenuation using a bunch of variables (mash temperature, yeast 
type, starting gravity, and beer color).  Here's a sample session 
demonstrating a linear fit to a bit of the data:

    > mashdata <- read.table('mash_temp_v_attenuation')
    > model <- lm(aa ~ sg, data=mashdata)
    > summary(model)

    Call:
    lm(formula = aa ~ sg, data = mashdata)

    Residuals:
        Min      1Q  Median      3Q     Max
    -7.3800 -2.1568 -0.0782  2.5637  7.9246

    Coefficients:
                Estimate Std. Error t value Pr(>|t|)
    (Intercept) 92.20718    5.05795  18.230 3.97e-12 ***
    sg          -0.30051    0.08643  -3.477  0.00311 **
    ---
    Signif. codes:  0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1

    Residual standard error: 4.296 on 16 degrees of freedom
    Multiple R-Squared: 0.4304,     Adjusted R-squared: 0.3948
    F-statistic: 12.09 on 1 and 16 DF,  p-value: 0.003113

This isn't exactly a very good fit, even if all the coefficients and the 
model itself are significant.  So far, my brewing hasn't shown mash 
temperature to be important in predicting attenuation.

Have fun!

Chris
- -- 
Christopher S.  Swingley          email: cswingle at iarc.uaf.edu (work)
Intl. Arctic Research Center            cswingle at gmail.com (personal)
University of Alaska Fairbanks   www.frontier.iarc.uaf.edu/~cswingle/



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Date: Tue, 12 Oct 2004 20:36:49 -0500
From: "Rob Moline" <jethrogump at mchsi.com>
Subject:  FOY, 2004 -Response- Published attenuation levels for various yeasts- Fred Johnson

	FOY, 2004 -Response- Published attenuation levels for various yeasts- Fred
Johnson

 Commercial yeast producers and others publish attenuation figures for
each yeast. Are these figures obtained using a standard protocol within
the company publishing the results? Are these figures obtained using a
standard protocol across the industry? If so, how does that protocol
relate to the vast array of wort compositions and fermentation
conditions that are encountered in the commercial brewery and in the
home brewery?
I suspect that the reasons yeasts vary in the degree to which they
attenuate wort are only partly known, but I would appreciate a brief
summary of what is known about this.
Fred L Johnson

Fred,
There is no standard procedure to determine the attenuation properties of
yeast strains. Usually yeast producers have internal standard wort and
conditions to compare the different yeast strains. But you are absolutely
right that wort composition and fermentation conditions vary from brewery to
brewery, which has a huge impact on attenuation. That is why we do not give
definite attenuation values for each yeast strain but put each yeast strain
in an attenuation group (High, medium, low) based on fermentation results
with our standard wort and fermentation conditions. This way the customer is
still able to select a yeast strain that suits best his beer style but they
have to determine the absolute attenuation under their specific conditions
for themselves.
The attenuation properties of a yeast strain depend on various factors.
Flocculation properties of a strain can influence attenuation; a very
flocculent strain that settles before the fermentation is complete will
leave more residual sugars in the beer than a strain that stays in
suspension longer.
Lager yeast usually attenuates relatively high whereas ale yeasts show
larger differences in attenuation depending on their metabolism. One factor
is the ability to use maltotriose.
Regards
Tobias & Forbes
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