HOMEBREW Digest #5505 Mon 16 February 2009

[Prev HBD] [Index] [Next HBD] [Back]

		Digest Janitor: pbabcock at hbd.org


                 Sponsor The Home Brew Digest!
     Visit http://www.hbd.org/sponsorhbd.shtml to learn how
    Support those who support you! Visit our sponsor's site!
********** Also visit http://hbd.org/hbdsponsors.html *********

DONATE to the Home Brew Digest. Home Brew Digest, Inc. is a 
501(c)3 not-for-profit organization under IRS rules (see the
FAQ at http://hbd.org for details of this status). Donations
can be made by check to Home Brew Digest mailed to:

HBD Server Fund
PO Box 871309
Canton Township, MI 48187-6309

or by paypal to address serverfund@hbd.org. DONATIONS of $250 
or more will be provided with receipts. SPONSORSHIPS of any 
amount are considered paid advertisement, and may be deductible
under IRS rules as a business expense. Please consult with your 
tax professional, then see http://hbd.org for available 
sponsorship opportunities.

  Should I repitch? (Tom Puskar)
  RE: yeast propagation (Joshua Wilkins)

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * The HBD Logo Store is now open! * * http://www.hbd.org/store.html * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Beer is our obsession and we're late for therapy! * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * NOTE: With the economy as it is, the HBD is struggling to meet its meager operating expenses of approximately $3400 per year. If less than half of those currently directly subscribed to the HBD sent in a mere $5.00, the HBD would be able to easily meet its annual expenses, with room to spare for next year. Please consider it. As always, donors and donations are publicly acknowledged and accounted for on the HBD web page. THank you Send articles for __publication_only__ to post@hbd.org If your e-mail account is being deleted, please unsubscribe first!! To SUBSCRIBE or UNSUBSCRIBE send an e-mail message with the word "subscribe" or "unsubscribe" to request@hbd.org FROM THE E-MAIL ACCOUNT YOU WISH TO HAVE SUBSCRIBED OR UNSUBSCRIBED!!!** IF YOU HAVE SPAM-PROOFED your e-mail address, you cannot subscribe to the digest as we cannot reach you. We will not correct your address for the automation - that's your job. HAVING TROUBLE posting, subscribing or unsusubscribing? See the HBD FAQ at http://hbd.org. LOOKING TO BUY OR SELL USED EQUIPMENT? Please do not post about it here. Go instead to http://homebrewfleamarket.com and post a free ad there. The HBD is a copyrighted document. The compilation is copyright HBD.ORG. Individual postings are copyright by their authors. ASK before reproducing and you'll rarely have trouble. Digest content cannot be reproduced by any means for sale or profit. More information is available by sending the word "info" to req@hbd.org or read the HBD FAQ at http://hbd.org. JANITORs on duty: Pat Babcock (pbabcock at hbd dot org), Jason Henning, and Spencer Thomas
---------------------------------------------------------------------- Date: Mon, 16 Feb 2009 09:54:54 -0500 From: Tom Puskar <tpuskar at optonline.net> Subject: Should I repitch? For a number of reasons ranging from illness, work and family issues, I have an IPA in the secondary for about 10 weeks. It looks clear and tastes decent upon sampling. I'm hoping to bottle it (FINALLY) this coming week and wondered if I should add some additional yeast for carbonation. I keep a few envelopes of dry yeast around and could proof one up and add it to the bottling bucket. I haven't checked the gravity in a few weeks but last check it was around 1.015 and hadn't changed for a while. Any thoughts? Thanks, Tom in Howell, NJ Return to table of contents
Date: Mon, 16 Feb 2009 21:27:27 +0000 From: Joshua Wilkins <jowilki3 at hotmail.com> Subject: RE: yeast propagation Hey all, I forgot to mention in my last post on air saturation that the times I gave were based on sterile filtered Air not O2. O2 will be a lot faster, but O2 also has the downside of creating oxygen free radicals which are very toxic to cells (same reason we get wrinkles). I used to use O2 in the past , but switched to sterile filtered air for that reason and because filtered air is cheaper than O2, but to be honest I have made good beer with both techniques. Fred asked: 1)Do you happen to know how Wyeast and White labs propagate the pitchable quantities of yeast they send to breweries intended to be pitched directly into their production batches. I quickly answered this before and the answer is no. I assume they do use aerobic methods because the biomass yield is much higher. I do know that one of them ships slurry in 2 liter bottles to be directly pitched into a 10 BBL batch (about 300 gallons) of beer. Of which, this slurry is in the dormant state (obviously because the bottle/bags would explode otherwise), but without activating this domant yeast (making a starter)with media of some kind, this will lead to a longer lag phase where the yeast adjust to the new environment as I have described before. This result WILL lead to longer fermentation times and in some cases lead to "off flavors". It all depends on what you are looking for in the beer. In some cases, these "off flavors" are desired, sometimes they are not they are simply process dependent. The smack packs that Wyeast uses contains nutrients and the sachet that you pop on the inside is the yeast cells. Once that sachet is broken they then begin to grow. So if timed right, the smack pack will be in the middle or end of the exponential growth phase when pitched. I say this is about 8 hours from when the sachet inside is broken. 2) I'd venture to say that the propagation is not customized based on the water profile and nutrients in the batch of wort at the brewery. Correct, they are based off many factors I am sure and probably deal a lot with what is cost effective, easily shipped, easily and quickly manufactured, "shelf stable" etc, etc. This is why a lot of breweries will simply order slants and then propagate up from there as follows (slant -> 1 Liter starter -> 30 L starter -> production tank (~3000 liters). 3) I also doubt that hops are even included in the propagation. To what part(s) of "hops" must the yeast produce "resistance"? Yea, I have no idea if they are or not. The problem comes in that if the yeast faces ideal conditions all the time, they get accustomed to that and will eventually drop the resistence gene/genes. The antimicrobial action comes from the bittering acids, (alpha acids being the largest portion), I am not going to name all of them here as there are many and the quantity all depends on the hop variety. As for the gene responsible for this in yeast, I am not sure of its name and a quick look on google scholar did not yield anything, but I did find an article on the development of hop resistence by beer spoilage bacteria. The gene family they have is call the Hor gene family and it acts by encoding "an ATP depen-dent multidrug transporter that extrudes hop bitter acids out of bacterial cells." I would imagine the yeast gene/genes does something similar, but I dont have anything to back that up. My main two points on yeast starters was this 1) Homebrewers dont have tools necissary to propagate yeast through exponential phase and keep them in aerobic growth. Yeast simply metabolize O2 too fast for this and equipment homebrewers use cant pump O2 fast enough into solution during this growth phase. Will aerating still result in higher biomass than other means, probably. Which brings me to point 2) Starters should get yeast cells into prime production shape with no surprises waiting for them in the fermentor which means whatever challenges will be faced in the fermentor should be seen in the starter, otherwise this will result in a longer lag phase and possible off flavors.This is also the reason the second batch usually tastes better than the first because the yeast had adapted during the first batch, yet genetic mutations due to yeast age (#of times replicated) are kept to a minimum, which is why yeast get changed out every 5-10 batches in commercial breweries. As for the Crabtree effect....Well my memory failed me (Doh). I was thinking it was a specialized case with Glycolysis-TCA cycle being preferred during aerobic growth, but I had them reversed. So Yes Crabtree effect keeps yeast producing alcohol whether its in an aerobic or anaerobic environment unless glucose is less than 0.2%w/w and Glycolysis-TCA cycle is reserved for specific cases. Last thing I promise; regardless of how people brew, if you are producing good beer that you are happy with, then by all means continue doing what you are doing. Joshua Wilkins Return to table of contents
[Prev HBD] [Index] [Next HBD] [Back]
HTML-ized on 02/16/09, by HBD2HTML v1.2 by KFL
webmaster@hbd.org, KFL, 10/9/96