HOMEBREW Digest #5606 Fri 11 September 2009


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


	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
		Digest Janitor: pbabcock at hbd.org


***************************************************************
        TODAY'S HOME BREW DIGEST BROUGHT TO YOU BY: 

                 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.
***************************************************************


Contents:
  Attenuation ("A. J. deLange")
  Re: Attenuation (Kai Troester)
  RE: Attenuation ("RJ")

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 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: Fri, 11 Sep 2009 08:26:46 -0400 From: "A. J. deLange" <ajdel at cox.net> Subject: Attenuation Attenuation is intended to be a rough indicator of the amount of specific gravity decrease over the course of a nominal fermentation with the yeast strain in question. Formally it is ADF = 100 X (OE - AE)/OE where ADF = "apparent degree of fermentation" (attenuation) in percent, OE = "original extract" and AE = "apparent extract". OE and AE are in grams of extract per 100 grams of beer i.e. extract concentration w/w i.e. degrees Plato but in common usage, especially by homebrewers, they are in specific gravity "points" (e.g. a wort with SG 1.040 has 40 points of OE). More meaningfull is the "real degree of fermentation" RDF = 100*(OE - TE)/OE where TE is the "true extract" of the beer i.e. the actual number of grams of extract in 100 grams of beer but measuring that is appreciably more troublesome that just taking a hydrometer reading on the fermented beer so few do it but you can estimate it from RDF = 3.271 + 0.766*ADF. I expect the answer to the question as to where the numbers on the yeast specs come from is that the manufacturer does test fermentations with nominal worts under nominal conditions for the particular strain (ale yeasts would be operated at higher temperatures than lager yeasts) and records the range of ADF's found. The ADF is going to depend on several factors such as the composition of the wort (dextrinous worts will not ferment to the same extent as highly fermentable ones i.e. ones mashed to produce lots of fermentable sugars as opposed to the larger, non fermentable ones), its OE, the presence of sufficient yeast nutrients and enzyme co factors, the temperature at which the fermentation is conducted, the pitching rate, the amount of oxygen supplied and when it is supplied and the, ability of the yeast to transport and lyse the various sugars available in a wort, the relative amounts of those sugars, how the yeast behave with respect to flocculation and their ability continue functioning as alcohol level increased. There are lots of variables here and that is why the manufacturer would have to pick some nominal set of conditions so that the results compare based on the properties of the yeasts themselves, (flocculation, alcohol tolerance...) and not on the conditions in the lab. But naturally, for these data to be useful to the brewer, the test conditions would have to be typical of the conditions found in the brewer's fermenter. All in all these numbers should be used only as a guide. If you prepare a 1.050 wort and ferment it with a strain rated at 75 - 80% attenuation you would expect that your final SG would fall in the range of 1.0100 - 1.0125. If it ends up at 1.020 then you would look for some cause (insufficient pitching rate, mash temperature too high, insufficient oxygen etc.) that might be responsible. Final note: a saccharification rest at 148 F would be expected to produce a more fermentable (higher attenuation) wort than one mashed at say 154 F. A. J. Return to table of contents
Date: Fri, 11 Sep 2009 09:35:46 -0400 From: Kai Troester <kai at braukaiser.com> Subject: Re: Attenuation Kevin, > I find attenuation ratings on a yeast strain confusing and I'm hoping > someone can explain it to me. Assuming the wort was mashed for a low > attenuation (say mashed at 148F) and the starting gravity was 1066. A > Munich Lager is used with an approx. attenuation rating of 75% (77% max). I > would end up around 1016 as a FG right (assuming correct aeration, nutrients > etc.)? But what determines this attenuation range on the package? Wouldn't > the yeast keep going until the fermentables were gone or the alcohol got too > high for the yeast? Why is it limited as per the strain rating? The attenuation numbers listed with the yeast strain are pretty useless and I wish they would not give them. Not only is there no standard in determining them, they also heavily depend on wort composition. I'd like yeast data that shows how good of an attenuator a given yeast strain is and how close to the attenuation limit (i.e. fermentability) of the produced wort a particular yeast will get in an average fermentation. Most of my thoughts about attenuation have been summarized in this article which is intended to answer the questions that you have: http://braukaiser.com/wiki/index.php?title=Understanding_Attenuation To illustrate the idea of the attenuation limit and that all yeasts can reach is it I one fermented samples of the same wort with a lager yeast (WY2206) and an English Ale yeast (WLP002) in fast ferment test conditions. This means warm, high pitch rate and occasional agitation. They both finished at the same gravity. This means that even an English Ale yest can be a good attenuator. But we don't necessarily want this to happen in our beers since the residual fermentable sugars that this yeast leaves behind by giving up early contribute to the character and balance of that style of beer. Kai Return to table of contents
Date: Fri, 11 Sep 2009 18:08:49 -0400 From: "RJ" <wortsup at metrocast.net> Subject: RE: Attenuation Kevin, Check out this web page at WhiteLabs http://www.whitelabs.com/beer/homebrew_terms.html Hope that helps RJ Return to table of contents
[Prev HBD] [Index] [Next HBD] [Back]
HTML-ized on 09/11/09, by HBD2HTML v1.2 by KFL
webmaster@hbd.org, KFL, 10/9/96