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	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
		Digest Janitor: pbabcock at hbd.org


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Contents:
  Reason for sugar residuals - (Energy/stress/biomassyield) ("Fredrik")
  Fortnight Of Yeast, 2004 - Published attenuation levels for various yeasts (Fred Johnson)
  Counterflow Issues (Grant Family)
  Curve Fitting ("Martin Brungard")
  Re: counterflow issues ("Spencer W. Thomas")
  Atteunation, yeast vs wort (correction) ("Fredrik")
  Pump Mounting ("Michael O'Donnell")


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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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JANITORs on duty: Pat Babcock (pbabcock at hbd dot org), Jason Henning,
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Date: Mon, 11 Oct 2004 07:47:37 +0200
From: "Fredrik" <carlsbergerensis at hotmail.com>
Subject: Reason for sugar residuals - (Energy/stress/biomassyield)

These are really interesting and head on questions! I think asking 
this to the fortnight experts is a great idea.

Just to stir the pot for the moment and through out some more wild
speculations...

 ..one working hypothesis that I intended to implement in 
the simulation(to see if it's consistent) is a kind of  energy 
flow model where there has to be a positive balance, 
of energy production and expensses. Expenses are of course 
biosynthesis, active transport of nutritions into the cell, and transport 
of waste out of the cell. Also I suspect stressful conditions increases 
the expenses in several ways. 

To account for this, I think it would be unnatural for the equilibrium 
residuals to be zero. I mean, who of us licks the plate after a meal?
A dog might say there is still plenty of food left on the plate. Ii's not 
wort the effort to lick the plate.

The maltotriose is the last to do, should be because it 
happens to be the most expensive food to refine, and different 
strains have different affinity to it (due to variable expression?).

I admit this is alot of theorizing and I may be wrong, but so far it looks
promising, so if anyone can point to flaws in my reasoning before I 
take it too far.  I would appreciate it.

Anyway I suspect the first thing that happens is that the biomass 
drops, of course the yeast by definition continues to grow all 
the way until they go dormant, but as sugar concentrations drop 
and stresses from waste products and nutrition depletion increases
the biomass yield drops. At some point, the biomass yield is so low 
that it is not favourable to "stay ative". The obvious suggestion to this 
treshold would be biomassyield roughly 0. However I am not sure, 
it's exactly 0? Any ideas? The biomass yield seems like a good 
choice of correlator to the energy stress level? 

That would suggest that when we see typical biomass yields of 5%, 
it might be alot higher in the beginning when nutritions are in excess 
and stress and production inhibition is low, and then drops. This is 
something that seems very consistent with the major boost in biomass
yield you get using a stirrer - even if no O2 is introduced. It reduces
stress and concentration gradients (which is also a kind of stress). The
only sensible explanation to this I've found is that the biomass yields
drop to basically zero during normal conditions, and the stress reduction
io biomass yields is major, rather than just some % one way or 
the other.

I think what needs to be done is to quantify this and put it all togehter
and see what it gives.

One question I intented to place to the fortnight is: Does the biomass 
yield basically drop to "close to zero" before dormancy? (this is what I
would speculate) If not, how low does it typically drop? 

Perhaps some of you guys has any comments to this? that perhaps even 
could lead to spin off questions to ask the experts?

 /Fredrik



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Date: Mon, 11 Oct 2004 06:36:50 -0400
From: Fred Johnson <FLJohnson at portbridge.com>
Subject: Fortnight Of Yeast, 2004 - Published attenuation levels for various yeasts

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
Apex, North Carolina, USA



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Date: Mon, 11 Oct 2004 23:32:33 +1100
From: Grant Family <grants at netspace.net.au>
Subject: Counterflow Issues

Hi all,

Today I bought a coil (18m/50ft) of 1/2 inch OD copper and would like to 
build a counterflow chiller (CFC), but I'm not sure if my setup will allow 
it. Here are the potential problems as far as I can see:

i) I don't have a pump and so would need to use gravity to feed the CFC. My 
boiler doesn't sit much more than a metre (3-3.5ft) off the ground and I'm 
unsure of whether I'll have troubles with gravity flow.

ii) My boiler (a keg with the top cut out) doesn't yet have a tap. As such, 
I normally have to syphon the chilled wort (chilled with a borrowed 
immersion chiller) out over the top of the keg and into the fermenter. Will 
this make syphoning through a CFC too slow and/or prone to clogging?

iii) I use only hop pellets and have no access to adequately fresh whole 
hops. Will this cause me untold grief in terms of trub in fermenter/loss of 
wort?

Any advice, especially from people who had/have similar problems, would be 
appreciated.
Thanks,
Stuart Grant,
Hobart, Tasmania, Australia.



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Date: Mon, 11 Oct 2004 05:12:22 -0800
From: "Martin Brungard" <mabrungard at hotmail.com>
Subject: Curve Fitting

Lately, there have been several comments on the difficulty of developing an 
equation for an existing data set (curve fitting).  There are software 
packages out there that can make the job much easier.

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.

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.  The program includes a number of curve 
fitting solutions, making it more likely that you will come up with a better 
equation for your data set.  For the limited work that most of us would 
likely use the program for, it is essentially freeware.  You can download 
the program from the following link.

http://curveexpert.webhop.biz/

For anyone dealing with developing equations for observed data, this is a 
great time saver.

Martin Brungard
Tallahassee, FL




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Date: Mon, 11 Oct 2004 10:40:27 -0400
From: "Spencer W. Thomas" <hbd-mod at spencerwthomas.com>
Subject: Re: counterflow issues

Stuart Grant asks:
> i) I don't have a pump and so would need to use gravity to feed the CFC. My 
> boiler doesn't sit much more than a metre (3-3.5ft) off the ground and I'm 
> unsure of whether I'll have troubles with gravity flow.
I've used gravity flow to pull wort through my CFC from a kettle sitting 
on the stove top.  The stove top is about 1 meter from the floor.
> 
> ii) My boiler (a keg with the top cut out) doesn't yet have a tap. As such, 
> I normally have to syphon the chilled wort (chilled with a borrowed 
> immersion chiller) out over the top of the keg and into the fermenter. Will 
> this make syphoning through a CFC too slow and/or prone to clogging?
Again, I siphon from my kettle.  I have a copper "racking cane" that 
reaches to the bottom "corner" of the kettle, and has a gentle bend at 
the top, so that the plastic hose doesn't kink.  I did have to buy some 
silicone tubing, as regular "vinyl" tubing is not safe for boiling 
temperature wort.  My vinyl tubing got very soft, and also I had 
problems with it introducing a plastic taste -- I had to dump 2 batches 
of beer.
> 
> iii) I use only hop pellets and have no access to adequately fresh whole 
> hops. Will this cause me untold grief in terms of trub in fermenter/loss of 
> wort?

I think that pellets may be easier to deal with than whole hops.  Whole 
hops can easily plug the end of the racking cane, while pellet hops 
should get sucked in, instead.  I whirlpool my wort at the end of the 
boil.  The hops & trub settle out into a cone in the center of the 
kettle, and by siphoning from the edge, they interfere very little with 
the siphon.  I also enclose the end of the racking cane in a copper 
"scrubbie" to help filter out those hops that do "wander" in that direction.

You can see a picture of this in action at
http://homeroastnbrew.info/homebrew/chilling/

=Spencer



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Date: Mon, 11 Oct 2004 18:31:01 +0200
From: "Fredrik" <carlsbergerensis at hotmail.com>
Subject: Atteunation, yeast vs wort (correction)

Thanks Fred Johnson for pointing out there a typo 
in me previous post. I post this correction of my previous 
post now to avoid further confusion for
anyone else who might read this.

In the definition of RDFW it should obviously be:

RDFW = Real Degree of Fermentabilit of Wort 
(=glucose+fructose+sucrose+maltose
+MALTOTRIOSE; % of extract)

the maltotriose term was missing in my last mail, sorry. 
(Where maltotriose = MTW)

RDFW = is supposed to be the maximum 
potential degree of fermentability.

 /Fredrik



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Date: Mon, 11 Oct 2004 10:56:16 -0700
From: "Michael O'Donnell" <mooseo at stanford.edu>
Subject: Pump Mounting

Hi all,

Probably a dumb question, but how important is it to mount a centrifugal 
pump in a horizontal position?  I notice that March recommends it, and most 
brewery pictures I see have them mounted that way, but I was just wondering 
what the considerations are?  Is it a fluids issue, or worry about wear on 
the bearings?

cheers,
mike
Monterey, CA



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