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	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
  Fortnight Of Yeast, 2004 - location of invertase action? / Philosophy and communication ("Fredrik")
  My Head Hurts (Jim Bermingham)
  Sugar utilization - Practical Phil, Intransigent Dave (ALAN K MEEKER)
  Wyeast storage time (Calvin Perilloux)
  Insulating Keg Kettles ("Mike Eyre")


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*               A Fortnight Of Yeast                    *
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Date: Fri, 22 Oct 2004 08:25:25 +0200
From: "Fredrik" <carlsbergerensis at hotmail.com>
Subject: Fortnight Of Yeast, 2004 - location of invertase action? / Philosophy and communication

I combine this post with another question to  
Tobias and Forbes. (The fortnight question at the bottom.)

- --------------------------------------------------
I feel a bit like a nucleation site and responsible for trigging the
bursts of parallell/serial issues lately. I also confess beeing
a yeast philospher :) 

The harder questions you ask, the more important does 
language, terminology and the proper construction of the 
question become.

IMO, in real life more often than not, many questions are indeed
fuzzy. While a computer would simply reject it as syntax error, 
a human philosopher will not do so, that is too easy.

Once a question is properly posed and technically well defined
answering it is often principally a matter of "computing" and thus
from a philosophers point of view - trivial. I find the learning
*process* itself intruguing. Sometimes I find the mechanism 
of concluding something more interesting that then conclusion 
itself. Facts are like matter, while the "why" is the essence of life.

My experience is that many real problems, and almost *all* of 
the most profound ones, are fuzzy questions, and does require
a "philosophical aspect" to solve them. You can not (currently) 
ask a computer something like, at what point of complexity
does matter turn into life? It is a fuzzy question, yet I find it
quite relevant and most humans does get the basic quest,
but we lack logic to deal with it. This is were a computer fails,
but a philosopher will invent new logic as needed. IMO one 
of the differences between a computing device and real 
intelligence is the capabiilty to invent new logic, and not turn 
into syntax error halts.

What I am trying to say is that some of this discussions look to
me a bit like we are computers here. I think everyone agree
the basic (fuzzy) question, we want to know how yeast behaves. 

Look at something like this (*just in principle*, beware for tyupos)

x = the entire set of variables, yeast, wort and fermentor 
(except time!)

dglucose/dt = - fg(x)*glucose*yeast_active + 
+ 0.5 * [ - fs1(x)*sucrose*invertase_wort - 
fs2(x)*sucrose*invertase_surfacebound ]
  
dfructose/dt = - ff(x)*fructose*yeast_active + 
+ 0.5 * [ - fs1(x)*sucrose*invertase_wort - 
fs2(x)*sucrose*invertase_surfacebound ]

dsucrose/dt = - fs1(x)*sucrose*invertase_wort 
 - fs2(x)*sucrose*invertase_surfacebound

dmaltose/dt = - fm(x)*maltose*yeast_active
dmaltotriose/dt = - fmt(x)*maltotriose*yeast_active

note that the equations account for the active yeast.
The dormant yeast does not consume wort sugars.
So once the yeast go dormant, the remaining sugars 
will be left as residuals.

f are different regulations. Let's assume some typical 
enzyme kinetics (michaelis-menten) this might be 
something like

fg(x) = ag(x) / { glucose + kg(x) }
ff(x) = af(x) / { fructose + kf(x) }
 ..etc

where ag() and kg() are further regulations to find out, so using 
knowledge, I will keep expanding thse regualtors, until I reach a 
level where it's reasonable to think thet are constants, then these 
will be my model parameters, and of course each parameters 
should be intristic to yeast, wort or fermentor. Ther must not be 
parameters that depend on everything. 
  
The problem would be to find these regulations. The model will 
be *crowded* with these regulation functions, and they must 
all satisfy balancing of energy, redox, carbon, nitrogen etc.

So training the model is to keep tweaking the regulation 
*functions* and also to tune in the parameters.

On thing I failed to find is if the invertase enzymes are cellbound 
or expelled freely into wort, or both??? I know that in theory 
there are both options but for brewing yeast I don't know 
which is relevant? I think I asked this question before on here 
long time ago but I got no comments.

Worst case I have to account for both, like above. Any ideas?

- -------------> Fortnight question to Tobias and Forbes.

(As speculated above)

Where is the location of action of invertase splitting sucrose? I 
wonder if it is all expelled into the wort, or if there is also 
relevant activity on the cell surface suface bound inverase? I 
remember reading some cells do have cellbound sucrose 
enzymes, what is that the case for S.C?

 /Fredrik



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Date: Fri, 22 Oct 2004 08:14:12 -0500
From: Jim Bermingham <JBHAM6843 at netscape.net>
Subject: My Head Hurts

My head hurts.  I think I have an "ose" headache.  With all the glucose, 
fructose and sucrose being batted around on the HBD and finding out that 
I am in the 1% minority of the HBD readers because I'm not sophisticated 
enough to understand Brettanomyces/Dekkera sp., my head is splitting.  
Here I am, just back from two weeks of lavish living in Sin City, 
Nevada, already feeling bad because I lost the shirt off my back and 
thought I would have to sell the farm just to pay my gambling debt. And 
instead of relaxing and settling back to enjoy catching up on all the 
post I missed  I get this feeling that all of a sudden no one is 
interested in brewing beer and sharing ideas on ways to improve their 
brewing. " I'm smarter than anyone else about most things, and I'm going 
to prove it" seems to be the attitude of the day.  Maybe I'm missing the 
point and if I was much smarter than I am I would see where all this 
would improve my brewing enough to beat Bev Blackwood in at least one of 
the brewing competitions.  But I still refuse to wear a skirt like Bev 
does.  He has better looking legs than I do.  I don't know if knowledge 
of the "ose" or his good looking legs is the key to all his ribbons.  
Enjoyed all the beers from The Chicago Brewing Company and the Triple 7 
Brewery while in Vegas.  If anyone happens to be in Millsap Texas come 
on by and we will have a few beers. Iif you can't come, send money I 
have some debts to pay.  Can't brew with two broken knee caps.

Jim Bermingham
Millsap, TX



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Date: Fri, 22 Oct 2004 09:23:52 -0400
From: ALAN K MEEKER <ameeker at mail.jhmi.edu>
Subject: Sugar utilization - Practical Phil, Intransigent Dave

My associate Phil Yates asks, what /practical/ use is there in discussing
the details of yeast sugar utilization? Well Phil you are correct, this
topic isn't likely to have much (if any) practical benefit to the average
homebrewer. Rather this falls into the class of more esoteric/technical
discussions that often take place here. Since the que has been short
lately these posts aren't displacing any other discussions, and there are
certainly folks interested in such details regardless of their potential
to directly help out one's brewing practice. Remember, the PgDn key is
always nearby... :)

Dave Burley commented: 

"As I have often in the past, I will forgive what I perceive to be an
arrogant tone and ask that you focus on the issue which you brought up."

 -What you perceived as arrogant was merely exasperation on my part. If
you re-read what I posted you'll see that it focuses /entirely/ and
succinctly on the one topic I brought up - that of sequential sugar use.

"I commented from the beginning of my discussion ( with /Fredrik) about 
glucose blocking certain pathways and many other comments relating to 
using a kinetic and not a misunderstood "energy" approach in /Fredrik's
<fermentation modelling> work."

 -What you ALSO said /repeatedly/ (which I cited in my last e-mail) was
that the concept of sequential sugar utilization was incorrect and that
this may be part of Fredrik's problem in modelling. This is what I 
responded to and is the only topic I have been addressing.  

"But as far as the discussion topic which you chose to open, about what happens 
in the yeast cell, as far as I know, glucose does not block the parallel 
assimilation of fructose or sucrose. If you have any evidence besides your 
opinion, I'd like to see it"

 -I never said glucose blocks fructose or sucrose. What I have said, and what 
was confirmed by Fischborn and Waldrop, is that glucose blocks maltose and
maltotriose uptake. Again, pretty simple idea. 

 -Alan Meeker



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Date: Fri, 22 Oct 2004 07:53:34 -0700 (PDT)
From: Calvin Perilloux <calvinperilloux at yahoo.com>
Subject: Wyeast storage time

[Robert Zukosky asks about the state of his nearly 4-year-old
 Wyeast smack pack that took 6 days to expand.]

Not to worry (much).  If the package expanded, you're probably
in good shape.  You'll have FAR fewer yeast cells than in a
fresh pack, though, so careful attention to starter sanitation
is recommended.  
 
You might also consider a multistage starter, beginning
fairly small (250 ml or even 100 ml?) before working up, 
since you are beginning with so few viable cells.  

I've used smack packs that have been in the fridge for 4 years,
and I've had normal fermentations with no problems or off-flavors;
this is when using at least a two-stage starter culture to get
the cell count up to something reasonable.  

Calvin Perilloux
Middletown, Maryland, USA



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Date: Fri, 22 Oct 2004 10:55:53 -0400
From: "Mike Eyre" <meyre at sbcglobal.net>
Subject: Insulating Keg Kettles

Hey all.. looking for info on good ways to insulate a keg mash kettle.
Did some searching on the matter and found surprisingly little info out
there. Saw some designs with a rather elaborate outside skeleton of
various materials, but that bulks up the keg a lot and they're heavy
enough for me to lift off the second rack of my gravity feed design. Saw
some others with some sort of jacket.. curious if this is the best
approach for light weight and easy access to the tun when needed.. what
are you all doing?

Mike




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