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HOMEBREW Digest #4329
HOMEBREW Digest #4329 Fri 22 August 2003
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
Digest Janitor: janitor@hbd.org
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Contents:
priming lagers (HOMEBRE973)
Sigh. Another worm... (Pat Babcock)
RE: Sanitizers and Septic ("Bridges, Scott")
CO2 being poisonous (Ed Benckert)
Water composition affecting Cold Trub formation? (FRASERJ)
Dr. Cone 2003 ("Sweeney, David")
CO2 tank safety (Calvin Perilloux)
unknown hops (Peter Collins & Sara Wilbur)
Re: How much priming sugar per bottle ("Tracy P. Hamilton")
DO Concentrations (mabrooks)
"waxy" starches (sedam)
anti-foam ("Kevin Kutskill")
Dr. Cone Responds- Yeast Flavours- Denny Conn ("Rob Moline")
BeerSmith 1.1 Software Released ("Brad Smith")
Dr. Cone Responds-Yeast Flavors-Steve B ("Rob Moline")
Dr. Cone Responds-Yeast for very high-gravity beers-Al Korzonas ("Rob Moline")
Dr. Cone Responds-Lager Pitching Temperature-David Lamotte ("Rob Moline")
Gump and Knowing It All ("Rob Moline")
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* The HBD Logo Store is now open! *
* http://www.hbd.org/store.html *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Beer is our obsession and we're late for therapy! *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* * * * * * * * IN PROGRESS! * * * * * * * *
* Dr. Clayton Cone Fortnight of Yeast *
* 8/11/03 - 8/22/03 Yeast Questions Answered *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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JANITOR on duty: Pat Babcock (janitor@hbd.org)
----------------------------------------------------------------------
Date: Thu, 21 Aug 2003 10:34:55 -0400
From: HOMEBRE973@aol.com
Subject: priming lagers
I am curious what is the general
view on priming lagers (beers that
have actually lagered at 32 F). Do
most people let the beer warm to
room temperature, then prime? Do
you store the primed beer at room
temp. or between 50 and 60 F, which
was the fermentation temp?
Thanks,
Andy in Hillsborough
------------------------------
Date: Thu, 21 Aug 2003 11:41:42 -0400 (EDT)
From: Pat Babcock <pbabcock@hbd.org>
Subject: Sigh. Another worm...
Greetings, Beerlings! Take me to your lager...
Folks, my apologies regarding the variable Digest timing of
late. The servers are spending the majority of their time
processing the product of those who have nothing better to do
than write worms and viruses - to the extent that there is
little processor time left for much else.
Bear with. I am manually triggering Digests when I see the gap.
On a positive note, the mail coming in indicates that a bunch
more ISPs are filtering such rot at their doorstep. This should
mitigate a lot of the traffic the worms generate. Next, they
should set their mail systems to simply quietly kill viruses,
rather than respond back to the falsified address. This would
reduce the traffic to the minimum...
- --
-
God bless America!
Pat Babcock in SE Michigan pbabcock@hbd.org
Home Brew Digest Janitor janitor@hbd.org
HBD Web Site http://hbd.org
The Home Brew Page http://hbd.org/pbabcock
[18, 92.1] Rennerian
"I don't want a pickle. I just wanna ride on my motorsickle"
- Arlo Guthrie
------------------------------
Date: Thu, 21 Aug 2003 11:46:44 -0400
From: "Bridges, Scott" <ScottBridges@sc.slr.com>
Subject: RE: Sanitizers and Septic
Sorry lost the original posters name....
>>Does anyone have information on using
>> sanitizers and it's effect on the septic system? I'm hoping that the
>> relatively small amounts I use for five gallon batches once a month or so
>> shouldn't be too detrimental.
>
>I do not have some sort of authoritative study where people threw iodophor
>in their septic system and studied the results, but it's pretty easy to see
>the scope without even crunching the real numbers.
>
>If you are mixing iodophor to taste-free sanitizing levels, and then
pouring
>that dilution into a septic tank of several hundred gallons, you are again
>diluting this so low that the few organisms you might kills off will
>regenerate within minutes, if not seconds.
I don't have any studies either, just personal experience. I've lived in a
house with septic tank for the last 17 years. I've been brewing with
various degrees of regularly for almost 15 yrs. I've gone back and forth
with numerous brewing cleaners and sanitizers along with regular laundry and
dishwasher detergents. I've never had a problem. YMMV.
Scott
------------------------------
Date: Thu, 21 Aug 2003 12:02:13 -0400
From: Ed Benckert <ed@ebonmists.com>
Subject: CO2 being poisonous
Tanksalot said:
I don't believe there would be a "rocket" flying around your brewery. CO2
is the gas used in many fire extinguishers so it's not poisonous or
flammable.
No, not flammable, but very very dangerous. Heres a link to a MSDS
(Material Safety Data Sheet) on CO2:
http://www.hoopersupply.com/msds/co2.htm
You dont need to be in a pure CO2 environment to suffocate and die (as is
obvious). It IS poisonous in concentrations. Ever stick your head in your
fermenting bucket and take a sniff of the beer, forgetting that theres a
blanket of CO2 on it? I have. Burns your sinuses out, tears your eyes up as
you vision goes dark for a second. I've done it. Thats not from not
inhaling oxygen, it's from the CO2 messing with your system.
------------------------------
Date: Thu, 21 Aug 2003 12:36:16 -0400
From: FRASERJ@Nationwide.com
Subject: Water composition affecting Cold Trub formation?
I moved from Westerville, OH to Pickerington, OH. Each had its own water
supply. Since I moved, I have noticed that I no longer get a thick
formation of cold trub after the counter chilling.
How does water chemical composition affect trub formation? Is there a
general rule of thumb on what I should add to my water to get my trub back
(its affecting my beers clarity after fermentation)??
John M. Fraser
------------------------------
Date: Thu, 21 Aug 2003 12:16:21 -0500
From: "Sweeney, David" <David@studentlife.tamu.edu>
Subject: Dr. Cone 2003
Dr. Cone:
My brain is about to explode with all of the biochemistry (they don't
call it BICH for nothing!). I took it in college but try not to think about
those horrible days.
In Fix's book _Principles of Brewing Science_, George outlines a list
of the most critical controllable elements of the brewing/fermenting
process for homebrewers, for example, fermentation temperature,
pitching volume, etc.
Since I is a Aggie, I have trouble with lists larger than I can count
on one hand. So my question is this: What are the top five
controllable variables (in order of importance) with regard to yeast
for the homebrewer?
David Sweeney
Texas Aggie Brew Club (TABC)
Millican, Texas
david@studentlife.tamu.edu
[1067.2 mi, 219.8 deg] (Apparent) Rennerian
------------------------------
Date: Thu, 21 Aug 2003 10:56:18 -0700 (PDT)
From: Calvin Perilloux <calvinperilloux@yahoo.com>
Subject: CO2 tank safety
"Tanksalot" wrote about the dangers of CO2 tanks:
>> Two years ago I had some 2.5# and 15# tanks refilled,
>> and foolishly left them in the trunk of my car...
Yow, I bet that was fun! I seem to remember that the safety
release vales are supposed to release gas (much!) slower than
a catastrophic decapitation, so no rocket effect for you, sadly,
just Little Ice Age in the boot! I bet any bystanders were
much impressed! (grin)
On that note, I also read from some vague source that CO2
is less prone to the "rocket" effect because unlike nitrogen
and many other common compressed gases, CO2 is in liquid/gas
form in the cylinder, and the evaporation of the liquid
provides a dramatic chilling effect and reduction of vapour
pressure which attenuates the explosive evacuation effect.
While that might sounds reasonable, the source did not
mention the degree of this effect. Enough to reduce any
damage substantially, or just a few insignificant percent?
>> [CO2] is the gas used in many fire extinguishers so it's
>> not poisonous or flammable.
It's not flammable, and not *AS* poisonous as things like
chlorine, but it is poisonous when present in amounts over
a few percent. I think a Google check might find the official
safety levels somewhere. I do know that when we converted
our IT shop some years ago from R-12 fire suppression to CO2,
we had some intense instruction on the risks. Unlike R-12,
argon, or nitrogen, which simply displace air, CO2 in high
concentrations can dissolve into your blood and cause some
effects ranging from unpleasant to dire. But you're right,
a whiff of even concentrated CO2 won't hurt you, er, except
the pain from those stinging nostrils!
Meanwhile, Keith Lemcke hopes for the day when we won't have
CO2 tanks but will get bulk delivery, similar to heating oil,
perhaps?
>> I hope any & all service establishments who change CO2 tanks
>> frequently will eventually move to bulk CO2 storage, which
>> uses a lower pressure stationary CO2 tank that is filled
>> from a bulk truck right at the service environment.
Fine for establishments that use a lot of gas, and I know Keith
isn't advocating that we homebrewers shift to such a system
(or I hope not), but let's hope that it's a not a big trend
that eventually makes CO2 standard delivery a large-scale
thing and filling of smaller tanks lots less profitable.
Sometimes it's hard enough for inidividuals to get tanks
refilled as it is.
Calvin Perilloux
Middletown, Maryland, USA
------------------------------
Date: Thu, 21 Aug 2003 14:19:22 -0400
From: Peter Collins & Sara Wilbur <sarapete@sympatico.ca>
Subject: unknown hops
Hi everybody,
I have some hops that a friend of mine gave me from his garden and he is
not sure what variety they are. Is there any way to tell their variety
by looking or smelling? Also, I have had them zip-locked in the freezer
for almost two years, are they still good? My initial plan was to use
them for dry hopping a pale ale but if there are other better uses for
them I am open to suggestions.
Thanks for your time.
Peter Collins
Cambridge, Ontario
------------------------------
Date: Thu, 21 Aug 2003 13:52:01 -0500
From: "Tracy P. Hamilton" <hamilton@uab.edu>
Subject: Re: How much priming sugar per bottle
A real simple rule holds:
If a 5 gallon recipe calls for 3/4 cup priming sugar, use 3/4 teaspoon
for a 12 oz. bottle. The reason this works is that 1 cup has 48
teaspoons and one batch has 48 12 oz. bottles.
Adjust appropriately for different size bottles, or for different
carbonation levels.
1 tsp for a Grolsch 16 oz bottle, for example.
Or 1 teaspoon in 12 oz bottle for a hefeweizen.
Tracy P. Hamilton
Birmingham Brewmasters
------------------------------
Date: Thu, 21 Aug 2003 12:13:34 -0700 (PDT)
From: mabrooks <mabrooks12@yahoo.com>
Subject: DO Concentrations
Date: Wed, 20 Aug 2003 09:53:19 -0400
From: Cairns Jim MTPROUS <Jim.Cairns@mt.com>
Subject: Re: Do levels
Date: Tue, 19 Aug 2003 12:20:27 +0000
From: "A.J. deLange" <ajdel@cox.net>
Subject: DO Levels
Gentlemen,
One could always use the "Winkler Method" (circa 1888)
of D.O analysis. It utilizes additions of divalent
manganese and a strong alkali, results can be
determined either visibly or via electrometric end
point. Though not many analysts are familiar with
this method, it is by far the most precise method
available for determination of DO. I used this method
on water samples years ago when I was in Grad school
and believe me it is tedious. Come to think of it, I
may just use it during my Fall water chemistry course
instead of the all too cheap and easy method of the
"Membrane probe". Wont the grad students love that!
Matt B.
Northern VA.
------------------------------
Date: Thu, 21 Aug 2003 17:34:29 -0400
From: sedam@email.unc.edu
Subject: "waxy" starches
Clarifying point on starches...what can I say...I can't resist.
There have been a couple of posts lately talking about "waxy" potatos
and the wax/oil content of that and other starches. There's a bit of
a nomenclature issue here, althought the content of the previous posts
(mostly in yesterday's HBD) were spot on.
Starch chemists (geeks that we are) use the term "waxy" to refer to
grains/tubers having high amylopectin content. So you can have waxy
corn, waxy potato, waxy rice, etc. None of these have excessive
amounts of wax or oils. Just that if you analyze the starch content
they'll usually have >95% amylopectin. I suppose they're called waxy
because when you gelatinize the starches they will tend to "set up"
firmer than the high amylose starch grains. Who knows...never trust a
cereal chemist with marketing. As an aside, the high amylose starches
are often refered to as "Hylon" starches...although this is the trade
name of a corn hybrid from my former employer.
Starchily yours,
Marc
- --
Marc Sedam
Chapel Hill, NC
------------------------------
Date: Thu, 21 Aug 2003 18:40:25 -0400
From: "Kevin Kutskill" <beer-geek@comcast.net>
Subject: anti-foam
Brian from Winnipeg mentions:
>Hop Tech must love you if you are using it up at that rate. I found 1/4 tsp
>of their product was lots, sometimes all it took was a few drops. It
depends
>largely on the wort and yeast. I've switched to FermCap now. Picked up a
>lifetime supply from a defunct brew pub for a pittance.
Call me the anal brewer. Hop Tech's directions state 1 tsp. per 5 gallons.
Didn't think on trying less (which I will for the next brew session).
It is nice to not worry about blow off tubes, though.
I was originally looking for a source for FermCap, when I found Hop Tech's
Foam Control. Anyone out there know of a good source for FermCap for a
homebrewer?
Kevin
beer-geek@comcast.net
------------------------------
Date: Thu, 21 Aug 2003 21:00:15 -0500
From: "Rob Moline" <jethrogump@mchsi.com>
Subject: Dr. Cone Responds- Yeast Flavours- Denny Conn
Dr. Cone Responds- Yeast Flavours- Denny Conn
Dr. Cone,
First, thank you so much for giving us some of your time.
My question concerns yeast growth as it relates to flavors in beer. I
have read several articles mentioning that yeast growth is important to
flavor production in beer, and that the amount of yeast growth is related to
the amount of yeast pitched. My own completely unscientific experiments
have
lead me to believe that I produce more "interesting' beers when I, for
instance, repitch only part of the yeast slurry from a previous batch
rather than the entire amount. The conventional wisdom in the homebrew
world seems to be to use the entire previous slurry to produce short lag
times. Is there a relationship between yeast growth and the flavors
produced in beer? Is it better to pitch an entire previous yeast slurry,
or is there a benefit to using a large, but not entire, amount of
slurry? I apologize for the vagueness of the question, but I have no way
to quantify the exact amounts I've been using. It's simply either "all" or
"part".
Thank you again.
Denny Conn
Denny Conn,
Ester and other flavor component production or synthesis is a complex
subject because there are so many variables taking place at the same time.
You are right, ester production is related to yeast growth but not in the
way you might think. The key element to yeast growth and ester production is
acyl Co-A. It is necessary for both yeast growth and ester production. When
it is busy with yeast growth, during the early part of the fermentation, it
is not available for ester production. Ester production is directly related
to biomass production. Everything that increases biomass production
(intensive aeration, sufficient amount of unsaturated fatty acids,
stirring) decreases ester production. The more biomass that is produced the
more Co-enzyme A is used and therefore not available for ester production.
Anything that inhibits or slows down yeast growth usually causes an increase
in ester production: low nutrient, low O2. It has been noted that a drop in
available O2 from 8 ppm down to 3 ppm can cause a four fold increase in
esters.
Stirring in normal gravity decreases ester production. Stirring in high
gravity increases ester production. CO2 pressure in early fermentation
decreases ester production. Taller fermenters produce less esters than
short fermenters. High temperature early in fermentation decreases ester
production. High temperature later in fermentation increases ester
production. Low pitching rate can result in less esters.
There are other flavor components such as higher alcohol that have there
own
set of variables. Stirring increases production of higher alcohols. CO2
pressure does not effect the production of alcohol. Amino acid levels in the
wort effect the production of higher alcohols. Most of the higher alcohol
is produced during the growth phase (exponential phase) of the yeast.
I am sure that there are many other variables. I am also sure that there
are beer makers that have experienced the very opposite with each of the
variables.
Pitching rates depend on several factors:
(1) The speed in which you wish the fermentation to take place. Some
professional brew master are in more of a hurry than others; desired beer
style, shortage of fermenter space. Pitching rates would vary as a means to
increase or decrease the total fermentation time. 10 X 10/6th cell
population for normal fermentation rates. 20 X 10/6th or more for a quick
turn around.
(2) Temperature control. If lack of refrigeration is a problem, the
fermentation needs to be spread out over a longer period by pitching with
less yeast.
(3) Health of the pitching yeast. If the pitching yeast has not been
stored
under ideal conditions (4C for less than one week) then larger pitching rate
must be done to compensate for the deteriorate of the yeast. Increased
pitching rates has its limits in trying to compensate for poor storage
conditions.
(4) When all other variables are under control you can use variations in
pitching rates to achieve certain flavor profile that are of interest to
you.
Conventional wisdom regarding pitching rate can lead to problems. During
each fermentation cycle the yeast will increase in size about three times,
so if you use all the yeast from the previous batch you will soon be
pitching with a huge amount of yeast. Professional brewers usually re-pitch
with about 25% of the yeast from the previous batch.
Proper handling of the yeast during storage (4C and <7 days) will
minimize
any problem with long lag phase. Start with a fresh culture of yeast after
about five recycles for bacteria control and or after 10 - 15 cycles for
genetic drift purposes.
There are many who will say that they are proud of the fact that they
have
used the same yeast after over 100 cycles. More power to them. I wish that
I could explain their luck. Good practices suggest frequent renewal with a
fresh culture is a good policy.
Thank you for your very good question.
Clayton Cone
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Outgoing mail is certified Virus Free.
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------------------------------
Date: Thu, 21 Aug 2003 22:12:58 -0400
From: "Brad Smith" <beersmith@beersmith.com>
Subject: BeerSmith 1.1 Software Released
I'm pleased to announce that BeerSmith 1.1 has
been released. Its a very cool piece of brewing
software with all of the features a home brewer or
professional might expect...
View the features and download a trial version at:
www.beersmith.com
Thanks!
Brad Smith
------------------------------
Date: Thu, 21 Aug 2003 21:21:33 -0500
From: "Rob Moline" <jethrogump@mchsi.com>
Subject: Dr. Cone Responds-Yeast Flavors-Steve B
Dr. Cone Responds-Yeast Flavors-Steve B
If this is a naive question please forgive, but what is unique about the
different strains of yeast that would allow them to create/impart different
flavors? Is it something with the biological make-up of a particular strain
or some other native charachteristic to yeast metabolism? As a follow-up
can the yeast organism be sufficiently isolated to "breed" for particular
flavor profiles?
Thanks
S
Steve,
This is a very complex subject that genetices and other researchers are
only
beginning to understand and believe me, I really have only a rudimentary
understanding of what is going on inside the yeast cell. It is in the
genetic make up of each strain. Each strain does almost the same thing as
another strain (of the same specie). However over the eons of time each
strain has had to express certain enzyme systems over others in order to
cope with its particular environment: nutrient source, climate etc. With
millenniums of time, these slight changes in the enzyme systems have become
permanente fixtures in its genetic make up. These slight changes give you
the rich variations in flavor by-products from strain to strain; the
different abilities to handle the sugars especially maltotriose in the wort;
the ability to function better at cool or warm environments; etc and etc.
Many thousands of strains are in nature waiting to be discovered. It is up
to interested parties (brewers, winemakers, bakers, researcher etc.) to go
out looking for them. Pardon my clumsy way of explaining the various
strains.
These various strains can be identified only by DNA fingerprinting.
The different genus, species and strains can and are isolated and can and
are being breed or mated. With out much success. First, there are so many
different strains in nature with all the wonderful characteristics that we
are looking for that screening nature seems simpler than breeding. Breeding
or mating can be done but it is not always simple. Some yeast are made to
sporulate. The spores of different strains or species with favorable
fermentation characteristics are mated. The off spring sometimes carry the
best of both strains but often time they also carry undesirable weakness of
one of the strains; slow fermentation rates, H2S production etc. Often
times they change after several generations.
The problems are the same with the fusion technique. The cell walls of
two
different genus are dissolved and the cytoplasm, nucleus and DNA of each are
mingled. The resulting off spring can carry the best of each parent but more
often carry bad luggage from one of the parents. They often do not remain
stable after several to many generations.
Genetic engineering is the most promising approach to producing a
designer
yeast that will produce the ideal beer, but at this time our society will
not accept this approach. Breeding is OK. GMO is not.
Thanks for your good question. It was not easy to answer. Please ask
more
if my answer still leaves you puzzled or whets you appetite for more
information.
Clayton
- ---
Outgoing mail is certified Virus Free.
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------------------------------
Date: Thu, 21 Aug 2003 21:32:22 -0500
From: "Rob Moline" <jethrogump@mchsi.com>
Subject: Dr. Cone Responds-Yeast for very high-gravity beers-Al Korzonas
Dr. Cone Responds-Yeast for very high-gravity beers-Al Korzonas
Dr. Cone--
When making a Barleywine or Doppelbock or Imperial Stout, is it better
to use the entire yeast cake from a previous batch of lower-gravity
beer or is it better to use just part of that yeast cake (half? 1/3?
2/3?) so that there is some growth?
In a related question, I've read that a significant portion of the
esters are produced in the growth phase. Can you confirm or correct
this assertion and comment on whether strong lagers may benefit from
a larger pitching rate for *this* reason?
Thanks.
Al Korzonas
Al,
From some of my replies to other inquiries, you have probably gathered
that
subject of pitching rate and flavor formations is very complex.
Usually you have to pitch at a higher rate for high gravity beers. The
general rule of thumb regarding pitching rate is one million yeast cells per
ml. wort per degree Plato. This is a good guideline if you have good yeast
storage and handling practices: 4 C. for <7 days. As you deviate from these
conditions it would be wise to increase the pitching rate a little. If you
have an accurate way to measure the yeast population and vitality in your
yeast cake great. If you do not, then I would start with 1/2 of the cake
the first time then adjust up or down as needed the next time.
The opposite of what you read is usually true regarding the increase in
ester production during the growth phase. During the growth phase the ester
production is reduced because acetyl-CoA is used for yeast growth and not
available for ester production. Higher pitching rates will result in higher
ester formation because there is less growth before they reach the
stationary phase. Higher pitching rates are also required for the yeast to
reach complete attenuation. Higher gravity wort is less friendly to the
yeast than low gravity wort.
Also, the higher the initial gravity the higher is the ester production
because there are in general more metabolites produced that can react with
each other.
Thanks for your good question.
Clayton Cone
- ---
Outgoing mail is certified Virus Free.
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------------------------------
Date: Thu, 21 Aug 2003 21:39:35 -0500
From: "Rob Moline" <jethrogump@mchsi.com>
Subject: Dr. Cone Responds-Lager Pitching Temperature-David Lamotte
Dr. Cone Responds-Lager Pitching Temperature-David Lamotte
Dr. Cone,
I would like to add my thanks to you for your generous contributions,
and to the previous posters for their thoughtful questions.
From previous discussions on the HBD and a number of brewing texts,
there appears to be two schools of thought regarding lager yeast
pitching temperatures.
One suggests that you pitch a lot of yeast at or below the fermentation
temp (8-12C) in order to minimise that amount of esters etc produced.
The other suggests that you pitch the normal amount at ambient room
temperature and begin cooling down to your fermentation temperature once
the first visible signs of fermentation begin.
My concern with the second method is that the fermentation will proceed
at too high a rate unless you have a large 'cooling power' available.
Do you have any information on the effect that pitching temperature has
on lager fermentations.
Thanks again,
David Lamotte
Fermenting in Newcastle, NSW, Australia
David,
You are right to be concerned about controlling the temperature of a
fermentation if you do not have adequate refrigeration. The higher
temperature generates heat faster and must be removed to keep the
fermentation from getting out of control.
Usually the higher the fermentation temperature the higher the ester
formation. However, the more yeast growth that you have at the higher
temperature the less acetyl-CoA is available for ester formation. So higher
temperature at the beginning produces more yeast and less esters while
higher temperatures during the stationary phase produces more esters.
I am not sure that pitching a lot of yeast in order to minimize ester
production is actually what happens. The lower pitching rate should give you
less esters. Acetyl-CoA is necessary for yeast growth and ester production.
When it is tied up in yeast growth it is not available for ester production.
The total amount of new yeast produced is dependent on pitching rate. The
lower pitching rate will produce more total yeast before it reaches the
stationary phase than the high pitching rate. The final yeast population
will be almost the same for both pitching rates.
I am including some comments and references from my colleague Dr. Tobias
Fischborn, a researcher at Lallemand research center and also on staff at
Siebel Brewing School, just to give you some idea how complex the subject of
esters , higher alcohol and other flavor components is.
Tobias' comments:
As always things are more complicated that they should be:
Esters usually decrease with higher biomass production because
acetyl-CoA is used for yeast growth (lipid synthesis). (Rose & Harris,
Narziss, Kunze). But low nitrogen concentration also decreases ester
production although less yeast is produced. In a high adjunct wort where
the ratio fermentable sugar to assimilable nitrogen (C:N ratio) is high
assimilable nitrogen is the limiting factor, excess yeast metabolites do
not accumulate and so ester syntheses is lower. In 100% malt wort the
C:N ratio is low, oxygen is the limiting factor and when growth ceases
assimilable nitrogen is still abundant and yeast metabolites, including
acetyl-CoA accumulate intracellularly and stimulate ester formation.
(Rose, A.H. & Harrison,L.S.: "The yeast" Vol. 5, p. 43)
Fusel alcohols: Anything that stimulates yeast growth causes an increase
in the fusel-alcohol concentration in the fermenting wort. (Rose, A. H.
& Harrison,J. S.: "The yeast" Vol. 5, p. 34). Low nitrogen content
increases fusel alcohol production.
In all 3 books they do not talk about pitching rate but other growth
stimulating factors like oxygen, high concentration of unsaturated fatty
acids and sterols. I agree that these are more important then pitching
rate (only for this reason):
If you have a low pitching rate and sufficient amount of oxygen you will
oxygen you have the contrary effect that you will produce more esters
compared to a higher pitching rate because you have more nutrients
"available per cell" and the yeast is accumulating acetyl-CoA which
stimulates ester formation.
On the other hand if you have a very high pitching rate you have only
limited yeast growth because you have only a certain amount of oxygen,
usually 8 mg/L, which is used very quickly by the large amount of yeast;
so most of the acetyl-CoA is not used for yeast growth. Unless you
aerate during the fermentation, which you should not do, you will have
more esters produced. Higher pitching rates are also associated with
higher organic acid and acetaldehyde production. (Narziss,L.: "Abriss
der Bierbrauerei", p. 211)
Other than that pitching rate is still very important. You do not want
to under pitch for various reasons. ----Tobias Fischborn
Thank you for your interesting question. Hope that my answers stimulat
you
to ask more.
Clayton Cone
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Date: Thu, 21 Aug 2003 21:55:33 -0500
From: "Rob Moline" <jethrogump@mchsi.com>
Subject: Gump and Knowing It All
Gump and Knowing It All
Now, Dave, anyone who knows me, I mean, really...REALLY (wink, wink!)
knows me....like YOU know me, Dave.....knows...
"The More I Know About Beer, The More I Realize I Need To Know More About
Beer!"
Gump!
From: "Dave Burley" <Dave_Burley@charter.net>
Subject: Gump and knowing it all
Brewsters:
Gump says he refuses to call me to inform me that he doesn't know it all. At
least that's what I think he meant. {8< )
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End of HOMEBREW Digest #4329, 08/22/03
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