From the HBD Archive
From: m14051@mwvm (John DeCarlo <m14051@mwvm>)
Subject: Fermenting at Cold Temps
Date: 1989-10-04 14:08:15 GMT

In Digest #261, Greg Crawford <Crawford.WGST129@Xerox.COM> writes:

>Also, could anyone tell me what effect fermenting at too cold a temp.
>would have. The yeast is a liquid german lager and the fermenting temp.
>is 40 degrees. (This was before I bought my hunter energy monitor).
>The beer fermented to completion but there is a strange background
>flavor I can't put my finger on. Infection has crossed my mind but
>I have tried two beers like this with the same results while my ales
>fermented at 70 degrees have had no problem

Well, I just got my copy of the special issue of _zymurgy_--the 1987 Special
Troubleshooting Issue (Vol 10, No. 4). An article in there, entitled
"Tracking Down Off-Flavors: A Brewer's Detective Story" investigates a brew
"variously described as meaty, onionlike, brothy, cooked vegetable, and
off-yeasty". (Talk about hard to describe.)

The article tells about the whole investigation, isolating various factors,
etc. but the gist was that the brew had a high level of methional, sometimes
described as "meat aldehyde". Simply by increasing the primary fermentation
temperature from 8C (46F) to 12C (54F), the levels of DMS, acetic acid,
and, most importantly in this case, methional were significantly reduced.

The article concludes with "We have all heard
so much about the well-established dire consequences of warm fermentations
that we tend to think, 'Well then, the colder the better.' It comes as a
shock to learn that cold fermentations also can lead to off-flavors. What
is really needed is the *optimum* fermentation temperature, not
necessarily the lowest at which our yeast will work."

John DeCarlo

ARPANET: M14051@mwvm.mitre.org (or M14051%mwvm@mitre.arpa)
Usenet: @...@!uunet!hadron!blkcat!109!131!John_Decarlo

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