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HOMEBREW Digest #4627
HOMEBREW Digest #4627 Wed 13 October 2004
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
Digest Janitor: pbabcock at hbd.org
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Contents:
Yeast carbohydrate consumption (Kurt Thorn)
Fortnight of Yeast 2004 - Repitching Yeast ("Steve Smith")
Kinetics and Thermodynamics ("Fredrik")
Electric Brewery ("richard")
Re: Kinetics and Thermodynamics ("Dave Burley")
Syracuse Beer Shops (elal)
News Scoop - National Beer Hall of Fame ("Dan Listermann")
March Pumps ("Jay Spies")
sequential sugar utilization by brewer's yeast (ALAN K MEEKER)
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* Questions submission: 10/11 - 10/22/2004 *
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Date: Tue, 12 Oct 2004 23:49:25 -0400
From: Kurt Thorn <Kthorn at CGR.Harvard.edu>
Subject: Yeast carbohydrate consumption
Hi all -
I just joined the digest after reading the archives for a while.
I have one comment on the discussion about whether yeast consume
carbohydrates serially or in parallel. In lab yeast strains (I suspect the
same is true for brewing strains, but have no proof), if glucose is present
in the media, the yeast will consume it preferentially. The presence of
glucose shuts down the synthesis of the transporters for uptake of other
sugars. I don't know if there is a hierarchy for other carbon sources
available to the yeast, but I suspect that if so, it is a less pronounced
effect.
Best,
Kurt Thorn
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Date: Tue, 12 Oct 2004 22:35:06 -0600
From: "Steve Smith" <sasmith at in-tch.com>
Subject: Fortnight of Yeast 2004 - Repitching Yeast
First, my apologies for such a basic question, but in my research I have
noticed that some people suggest reusing yeast by pitching wort over the
existing trub/yeast in a primary fermenter immediately after racking the
beer that had been on it into a secondary fermenter, or by harvesting some
of that yeast to use with the new batch of wort. Other people, including
Wyeast and/or White Labs and John Palmer provide information for washing
yeast when taken from the primary fermenter before repitching it. Or, if
timing is right, it is preferable to harvest yeast from the bottom of the
secondary fermenter at bottling time, or by top harvesting ale yeast as it
is found in the foam during primary fermentation. I recently reused yeast
for the first time. I opted to harvest a pint of yeast/trub (placed in a
sanitized jar) from the bottom of the primary after racking off the
all-grain beer, and repitched about half of the yeast/trub a couple days
later in a different style beer that called for that same variety of yeast.
The wort fermented practically over night (when I checked the gravity it had
dropped to the desired level). Did I follow an acceptable practice, or am I
likely to end up with off flavors in my second batch of beer off of the same
yeast (consider that I used good sanitation)? I realize that autolysis
could contribute to off flavors in the second batch if the yeast/trub was
exposed to wort for too long a period.. I had fermented on the trub for
eight days with the first batch, and plan on racking off the trub after five
days in the second batch.
Steve Smith
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Date: Wed, 13 Oct 2004 08:33:15 +0200
From: "Fredrik" <carlsbergerensis at hotmail.com>
Subject: Kinetics and Thermodynamics
I wanted to wait and see what the fortnight response is, but
since Dave Burley posted this comment perhaps others
think the same...
Thanks for your comments Dave,
I am not sure if I was able to explain myself properly, it's
always cumbersome to isolate something without posting all
definitions and math but to put it in context. I don't suggest
"energy states" as in equilibrium states. As the whole thing
with fermentation is all about dynamics what I meant with
energy energy FLOWS. And that is indeed kinetics.So
here I think I was unclear. I promise to post details on this
once it's done. The simulation will attempt to model the
kinetics, not equilibrium things. The model is not
some "FG = f(x)". The model is a set of DEs, that requires a
numerical solution/simulation. The model will contains a number
of made up functions that are supposed to mimic to my
understanding yeast responses on external changes. The basic
stuff, like depletion of sugar and production of alcohol is done,
the problem is to get the fine structure right, to model the stress
factors, and the exact attenuation. This is the hard part.
I need to quantify and decompose the different stress factors,
and model the exact dynamic biomass yield. I don't care if
it's tricky, I've already comitted to at least try. Or actually,
the fact that it's tricky is the whole point.
As far as I know some sugars are parallell, but some are not.
glucose fructose and sucrose are I think kind of parallell. But
these sugars are supposed to depress the uptake
rate of maltose and maltotriose. This is (among others),
according to Dr.Cone from last years fortnight.
Why activate yet another enzyme system
(this is a cost) when there is plenty of easy stuff left?
( Analogies:
The *idea* is no more strange than the fact that
a predator always aims for the weakest pray. It's certainly less
of an expense to catch the weakeast pray. However when the
weak prays become rare, does the fit prays become favourable
as well. It doesn't make sense running around the woods for a
day looking for a one-legged rabbit. )
You can't plug maltotriose nor maltose directly into the
glycolysis. There is an extra step of effort to prepare
maltotriose than maltose. Add to this the lower genetic
affinitiy for it. Further decreasing the effiency of uptake.
The balancing I suggest is between efforts and gain.
I suspect the offset that causes food to be left is stress
and cost of staying active. I would assume (but I may be
wrong as always) that trying to extract the last food, takes
a bigger effort than it gains. So it goes dormant. I think
this logic is crystal clear. If I have missed something let me
know. I think the hard parts is to mimic the regulation
that are genetically controlled. Quantify the effect of
stresses etc.
This seems to be the best candidate mechanism atm. Even
if it's not perfect I have to work with the best I've go for
the moment. I was hoping to get some further ideas/input
by posting it here.
/Fredrik
" TRYING is the first step towards FAILURE"
- -- Homer S
------------------------------
Date: Wed, 13 Oct 2004 22:08:57 +1000
From: "richard" <richard_beattie at optusnet.com.au>
Subject: Electric Brewery
Hi !!
I'm in the process of graduating to all grain and am setting up the brewery
now.
Batch size 5 gal - and I'd like to stay indoors - so my preference is an
electric brewery.
I've made a mash tun from an old esky (picnic cooler) - so mashing is taken
care of - but my choice for HLT and Kettle was going to be a BRUHEAT style
boiler - or something equivalent - bought off the shelf.
BUT - they seem to be totally unavailable in Australia now - so only option
is to convert some plastic buckets.
A very kind Home Brew shop in Melbourne gave me the tip off to use a cheap
electric kettle and pull the element out. I brought 2 from a large
department store for under A$10 and they look like they will do the job.
2400W at 240V. The elements are actually shiny metal.
Has anyone else used something similar? Any tricks for new players?? Any
feedback much appreciated before I start to install.
Also - anyone in OZ know a good supplier of plastic buckets. 20L ones seem
easy to get but I'm looking for a 30L bucket for the kettle.
Cheers.
Richard
Sydney Australia
------------------------------
Date: Wed, 13 Oct 2004 09:33:28 -0400
From: "Dave Burley" <Dave_Burley at charter.net>
Subject: Re: Kinetics and Thermodynamics
/Fredrik,
>( Analogies:
>The *idea* is no more strange >than the fact that
>a predator always aims for the >weakest pray. It's certainly less
>of an expense to catch the >weakeast pray. However when >the
>weak prays become rare, does >the fit prays become favourable
>as well. It doesn't make sense >running around the woods for a
>day looking for a one-legged >rabbit. )
Don't anthropromorphisize the yeast into a predator.
Think of yeast as a catalyst promoting a chemical reaction ( which
energetically is possible, but not kinetically rapid) via their enzyme and
transport mechanisms. The yeast do not wait or make energy decisions or look
for the weakest "prey".
If you were to start with all the same concentrations of carbohydrates and
look at the fermentation as it proceeds you will find some carbohydrates are
disappearing more quickly and the final result may be there are certain
carbohydrates left depending on many different conditons of the fermentation
as well as the yeasts' genetic makeup.
Point is, all of these carbohydrate reactions are proceeding at the <same
time>, <NOT serially>, as you suggest in your comments. Some are just slower
than others.
As you commented, there are some secondary interactions due to the
"interference" of certain sugars, but the point is all of these reactions are
going on simultaneously
Change your concept and model and it will more closely fit reality.
Keep on Brewin'
Dave Burley
------------------------------
Date: Wed, 13 Oct 2004 11:14:45 -0300
From: elal at isn.net
Subject: Syracuse Beer Shops
Thanks to the excellent assistance of HBDers, I discovered the delights of two
beer shops in the Syracuse, NY area which is about two hours drive from me here
in Kingston Ontario.
Galeville Grocery: http://www.genx40.com/archives/2004/august/galeville
Party Source: http://www.genx40.com/archives/2004/october/partysource
If anyone has any other upstate New York shops to check out, please let me know.
I know that Buffalo and Rochester has one great one each that I intend to
check out sooner or later but how about Utica or Rome or Albany? Any
assistance with my quest for beer shopping heaven is appreciated.
- --
Alan
www.genx40.com
------------------------------
Date: Wed, 13 Oct 2004 14:53:44 -0400
From: "Dan Listermann" <dan at listermann.com>
Subject: News Scoop - National Beer Hall of Fame
The people from the US Beer Drinking Team just called to tell me that the
National Beer Hall of Fame will be located in Cincinnati very near the
Downtown Convention Center in about 100,000 sq ft of prime commercial space.
Projected opening date 9-06.
Too cool! We will see if it comes about!
Dan Listermann
------------------------------
Date: Wed, 13 Oct 2004 15:11:32 -0400
From: "Jay Spies" <jayspies at citywidehomeloans.com>
Subject: March Pumps
All -
Martin Brungard makes some interesting observations regarding the orienting
of March and other mag drive pumps.....
>>>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.<<<
Yikes! I know that many people here on the HBD, as well as B3 (sponsor of
the HBD) use these pumps vertically mounted. I wonder if any other people
can chime in who have them mounted vertically (or otherwise) who've had
long-term experience with a non-horizontal configuration... Any pump
failures/mishaps? I have 2 of these pumps and they're mounted horizontally,
but that was by pure happenstance....
Jay Spies
Head Mashtun Scraper
Asinine Aleworks
Baltimore, MD
------------------------------
Date: Wed, 13 Oct 2004 16:51:35 -0400
From: ALAN K MEEKER <ameeker at mail.jhmi.edu>
Subject: sequential sugar utilization by brewer's yeast
In response to Fredrik's query Dave Burley wrote:
"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."
Actually, brewer's yeast do in fact utilize sugars in a sequential manner.
Fructose and glucose are utilized first (Even though they are lower
abundance wort sugars), before any appreciable processing of the major
malt sugars, maltose and maltotriose, occurs.
This makes perfect sense from the yeast's point of view because glucose
and fructose are the 'easiest' sugars to use from a metabolic efficiency
point of view. Maltose and maltotriose must first be converted to glucose
(hydrolysis of these sugars liberates glucose) before this can be plugged
into the metabolic pathway(s). Underlying the mechanics of this sequential
utilization phenomenon are the specific transporter proteins that bring the
sugars into the cell. It is not the case that all the transporters for all
the various sugars are synthesized and present on the cell surface at all
times. Such a situation would be energetically wasteful and would have been
selected against during evolution. Instead, for reasons of efficiency, the
yeast use the easiest substrates first, particularly glucose. In fact, when
glucose is present the yeast cell actively shuts down any production of the
proteins that are involved in the transfer and breakdown of maltose and
maltotriose. This is why there is a delay in maltose/maltotriose uptake and
metabolism; there are no transport proteins on the cell to bring these
particular sugars in. It is not until the glucose has been exhausted that
the maltose utilization genes are freed from glucose repression.
-Alan Meeker
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End of HOMEBREW Digest #4627, 10/13/04
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