From the HBD Archive
From: <LLUG_JI%DENISON.BITNET@CUNYVM.CUNY.EDU> (JOHN L. ISENHOUR)
Subject: Re: High Temperature Fermentation
Date: 1989-06-20 15:32:00 GMT

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@DENISON.BITNET

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