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	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
  re: Best pitched when? ("steve.alexander")
  re:open fermentation ("Ben Dooley")
  shout out to Wisconsin brewers! (Joe Katchever)
  Re: ("Upgrading Q. Februarys")
  re: Best pitched when? (Kevin Elsken)


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Date: Wed, 21 Jun 2006 03:06:13 -0400
From: "steve.alexander" <-s at adelphia.net>
Subject: re: Best pitched when?

Kevin Elsken of the 'burgh asks,

<<
when is a starter at optimum? [...] - is it best to let the 
starter completely ferment out and pitch the slurry?  Or is there a more 
optimum point in the cycle to pitch?  [...]
>>

That depends on which parameter you are trying to 'optimize'.

The general rule is that we want the yeast to take off readily
after the wort is cooled.  The primary reason for this is to prevent
infection, that is unwanted molds and bacteria from getting an early
foothold.  Of course there are many other goals one could consider.

You must realize that during a normal fermentation the yeast
metabolism undergoes numerous shifts.  If you pitch 'dormant'
yeast from an anaerobic starter which has finished, the yeast
begin to uptake oxygen and use internal carbo stores (ignoring
the wort sugars for a while).  Then they shift to take in the
mono-saccharides via a passive transport mechanism, then the
di- & tri- sacch's via a facilitated transport mechanism.  As
yeast growth trails off the yeast stop producing fatty acids and
instead produce AAT enzymes which mop up the fatty residues and
also produce esters.  Early when the wort amino acids are
plentiful, some may be used for energy, but late in the
fermentation when the aminos are low the yeast must
synthesize required aminos from the few types remaining of
from inorganic amine groups.  Either produces additional fusels.
Of course very late in the fermentation, brewing yeast undergo
rather extensive changes to the cell surface which cause
flocculation - later when repitched the cell surfaces must be
restored to their non-flocculent state.

So all throughout fermentation the yeast metabolism is shifting
and these shifts involve regulated changes to genetic expression,
and typically the production of enzymes to catalyze the
processes, and also as part of regulation. So the shifts cost
time and energy.   It might take 2o-60 minutes for healthy,
energetically sound yeast to shift from glucose only environment
to maltose induction. Probably much longer for compromised yeast.

At the completion of a normal brewery ferment the yeast are not
in ideal condition.  They've been O2 deprived, the osmotic pressure
from ethanol & the CO2 pH related inhibition have been taking up
valuable energy, and many amino acids have been missing for some
time.    In a starter you *can* do much better by using low gravity
wort 8-10P, continuous aeration as on a stir plate, and even a little
yeast nutrient.  Of course you can also make starters which are more
like mini-brewery ferments.

So if you are making top-notch starters as above, then I'd suggest
that should ideally pitch before the yeast flocculate, but this can be
quite late in the starter ferment - say 60+% apparent attenuation.
If your starters are more like brewery ferments, not continuously
aerated, normal grav, etc, then I'd suggest you pitch the starter
when the starter is about half-way through the ferment - say 35-40%
apparent attenuation.  You can slow down the starter by placing it
in a fridge and thus control the timing.

This evaluation is most useful at the utopian brewery. The reality is
that if you are making a 15P dark monster bock, and your starter is
made from well aerated 8P pale wort, that you *will* want to separate
out the aerated-stale, thin, pale starter wort and toss it.  Unless
you have access to a centrifuge that will take a few liters you'll
have to chill separate the yeast or let the fermenter finish and
flocculate.  The choice to invest in a $15k centrifuge or accept
healthy but flocculated yeast which may cause a minor fermentation
delay should be obvious to the HBers.

Anyway it is a useful gedankenexperiment.  The point to keep in
mind is that you must always be aware of whether you are trying to
make optimal beer or optimal yeast in a given ferment. The two goals
are at odds with each other !!
 
 -S

/**/



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Date: Wed, 21 Jun 2006 11:01:09 -0400
From: "Ben Dooley" <bendooley at gmail.com>
Subject: re:open fermentation

Thanks for the advice. I checked the beer out last night, and the
krausen is high. Is this the best time to harvest yeast? I thought I'd
skim some off and stick it in the fridge to use for the next batch.

Thanks again for the help.

Best,

Ben


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Date: Wed, 21 Jun 2006 11:39:33 -0500
From: Joe Katchever <joe at pearlstreetbrewery.com>
Subject: shout out to Wisconsin brewers!

I'd like to get in contact with the homebrewers in the area. I live in 
La Crosse, Wisconsin; on the bank of the mighty Mississippi. Any nearby 
Minnesota homebrewers give me a shout, too. I'd like to organize a 
homebrew club. I know there are several homebrewers in the area, but no 
one seems to know one another. email me at joe at pearlstreetbrewery dot 
com.

Egor the Orange




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Date: Thu, 22 Jun 2006 04:49:35 -0700
From: "Upgrading Q. Februarys" <msk at goooo.3322.org>
Subject: Re:

welco me to the best pharmacy http://milesesto.com/?IJESRKQV1AQHVZUFcaWkNV



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Date: Thu, 22 Jun 2006 22:32:45 -0400
From: Kevin Elsken <littleboybrew at verizon.net>
Subject: re: Best pitched when?

Steve, as always thank you for the informative reply.

My normal mode of operation is to use dormant yeast.  I have been in the 
habit of making starters in the 8-10 P range (I have read your 
recommendations before), but I do not have a stir plate or method of 
feeding oxygen.

Suppose I had I liter or starter that had fermented out and 
flocculated.  If I drained off the spent wort starter and added, I don't 
know, say 500 ml of fresh pre boil wort to the slurry, that would give the 
yeast maybe 2 hours to wake up prior to pitching into the fully finished 
beer (by the time I run off all the wort and boil and cool).  Would that be 
enough time to make a difference, or would I be better off to make 500 ml 
of fresh starter say 24 to 48 hours before brewing and pitch the slurry 
into that?

Kevin



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