HOMEBREW Digest #182 Wed 21 June 1989

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		Rob Gardner, Digest Coordinator

  Re: High Temperature Fermentation (JOHN L. ISENHOUR)
  contact (Kurt Baudendistel)
  specific gravity problems, over-carbonation ("1107-CD&I/VIRUS DISEASES")

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---------------------------------------------------------------------- Date: Tue, 20 Jun 89 11:32 EDT From: <LLUG_JI%DENISON.BITNET at CUNYVM.CUNY.EDU> (JOHN L. ISENHOUR) Subject: Re: High Temperature Fermentation I have had fairly good luck with high temperature fermentation. I have not run into increased temperature causing incomplete fermentation, it just seems to react much faster. The problem with incomplete fermentation may be that the yeast metabolism causes the temperature of the wort to increase about 6 or 7 degrees F, this can shock the yeast, so it is most important to control the temperature during the initial ferment when the total metabolic rate is highest. I have made some good ale at 75 degrees F., but have had it 'flash ferment' where the entire ferment lasted less than 48 hours and was fully primed after 3 days! I believe what causes most problems is the 'window' of contamination, where the yeast has not gotten a good start and the media is subject to infection from other agents. Once the yeast has a good hold on the wort, it tends to repel invaders by changing the PH of wort so that anaerobic ferments dont like it, and creating an anaerobic environment so aerobes dont want it either. In the summertime I am especially careful to get a large quantity of yeast going, I usually use about 5 packs of edme per 15 gallons wort. It is best to start it in fairly hot (95-100 d.F) water, not wort, as yeast likes initial hydration to be with just water, then added a thick wort to that, I generally start mine in a very large yeast culturing flask (I think its about 3 liters) several hours before pitching, its usually going like mad. I pitch when the wort is around 95 degrees, I usually get a good head on the primary within about 6-8 hours. When I use lab culture yeast, I also get it started, I dont feel that Wyeast packs contain enough yeast for a really secure start, I allways transfer it into a mason jar full of sterilized wort with a lock rigged on and let it really get going. Check for the upcoming special issue in Zymurgy on yeast, I have an article on sterile transfer and propagation in it. Over the years, when the temperature is high, I have been going to refrigerator fermentation, just to take the edge off the ales. I found I have to have a large stockpile to do lagering properly, or I get impatient. I have used my spare bathtub as temperature control, If you use ice or water bath remember that it is probably better to have a constant but warmer temperature than to have the brew changing temperature radically up and down. John L. Isenhour LLUG_JI at DENISON.BITNET Return to table of contents
Date: Tue, 20 Jun 89 12:57:51 EDT From: hplabs!gatech!baud (Kurt Baudendistel) Subject: contact mr. homebrew, i've not had any contact with the homebrew organization in a long time. wasn't there a mailing list or something? kurt Return to table of contents
Date: 20 Jun 89 13:40:00 EST From: "1107-CD&I/VIRUS DISEASES" <henchal at wrair-emh1.army.mil> Subject: specific gravity problems, over-carbonation John Mellby writes "I am having {problems} with my ale. In the last leveral batches I have a high terminal gravity between 1015 and 1020." You don't mention what your starting gravity was, but you can expect the attenuation of your ale (the differnece between the starting gravity and the final gravity) to be between 65-80%. The factors which affect the final specific gravity are as follows: 1. The strain of yeast. Wyeast and other suppliers are now providing the attenuation characteristics of their yeasts. This data is helpful for when you craft beer. You can select yeasts to be light (with high attenuation) or strong (with low attenuation) body depending upon your desires. 2. The extract. The way that the grain was mashed significantly affects the final gravity. Some extracts are made at higher mash temperatures which result in a greater proportions of limit dextrins in the malt extract. If you are a grain mash/brewer this is one of the characteristics you can control. The length of time you mash the grain at the saccharifying temperature also controls the amount of dextrins in the extract. Wworts with a higher percentage of dextrins have lower attenuation and high final gravities. 3. Contamination. Contamination of the primary fermentation can result in a "stuck" fermentation. In this case, yeast and contaminating microorganisms compete for essential nutrients. The fermentation cycle is interrupted by the decreasing efficiency of the yeast to perform the intended job. John also writes, "...and despite using as little as 1/2 c of sugar for priming 5 gallons, the bottles are over-carbonated." The most common cause of over carbonation, if the correct amount of priming sugar is being used, is bacterial contamination. For a detailed discussion see the Troubleshooting Issue of Zymurgy. I hope that this is helpful. ERIK A. HENCHAL <Henchal at WRAIR.ARPA> Return to table of contents
End of HOMEBREW Digest #182, 06/21/89
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