HOMEBREW Digest #5025 Thu 22 June 2006

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  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 /**/ Return to table of contents
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 Return to table of contents
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 Return to table of contents
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 Return to table of contents
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 Return to table of contents
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