From the HBD Archive
From: Richard Childers <rchilder@us.oracle.com>
Subject: Yeast Cultivators' Literature
Date: 1992-03-17 19:08:31 GMT

"Date: Mon, 16 Mar 1992 17:05:45 -0600
From: Kathleen T Moore <ktmg8824@uxa.cso.uiuc.edu>
Subject: yeast culturing

"Can anyone and everyone who has experience with yeast culturing please send
me detailed info on the process. I am interested in all aspects and every
level from the simplest homebrew processes to the most elaborate brewery
techniques (at least those used by micros and brewpubs.) I have had a basic
microbiology class in college, but I need specifics such as media recipes
for stock culture maintainance and media recipes for selection and separation
of bacterial contaminants and wild yeast identification. Also, does anyone
know of a book or article describing the aforementioned subjects with regard
to microbrewery applications? I have access to a small incubator and also to
a small autoclave, plus incidental equipment. Eventually, I would like to
develop a standard procedure for stock maintainance and purity analysis for
homebrewers who are courageous enough to venture into this realm."

Interestingly enough, Kathleen, I was just going to post this little review
of just such a book. I picked it up a few weeks ago, browsed through it last
night ( while quaffing my latest ale, of course ) and found it worth sharing.

Yeast Culturing For The Homebrewer
by Rog Leistad
Copyright 1983 by Rog Leistad
Published by G W Kent, Inc.
3691 Morgan Road
Ann Arbor, MI 48108

Here's part of the table of contents :

Introduction pages 1-2
Chapter One, Equipment Needed for Culturing Yeast pages 3-6
Chapter Two, Yeast Starters page 7
The Canning Method pages 8-11
The Pressure Cooker Method pages 12-14
Chapter Three, Yeast Cultures page 15
Stage 1, Activating The Yeast pages 17-19
Stage 2, Preparing Agar Slants pages 19-20
Stage 3, Inoculating The Agar Slants pages 21-23
Care Of Your Slants page 23
.
.
.

You get the idea.

I'd type in the Introduction, but I'm short on time. Let it be noted, however,
that he addresses the fact - until now unacknowledged in these ivy-covered
halls of digitized knowledge - that stocks mutate, and that there is No Good
Way to keep this from happening, except to keep refreshing your stock.

His method is to take one liquid culture of known goodness - presumably,
fresh from a manufacturer - and making cultures out of it. ( I suppose that
the legal mind that would copyright roses' genetic patterns would also take
umbrage at this illicit cultivation of a copyrighted slimemold - and if
this is not an issue now, it will be soon. Take note, brew clubbers ... )
He admits to cultivating multiple generations of yeasts hard to get, such
as those harvested from the bottoms of beer bottles, but even so, warns
against the inevitable mutation.

It seems to me that, given the speed with which yeasts propogate, and the
speed with which the generations pass, that evolution is a tangible force
in the brewing world, and cannot be stopped or countered. The best one can
do is to try to keep known good cultures on hand, ruthlessly discard those
that go bad ( optionally killing everything in the flask first, if you're
really interested in influencing evolution, :-), and keep a steady flow of
new genetic strains moving through your beer, accepting the inevitability
of your beer's changing as the yeasts mutate in response to environmental
stresses and influences. Keep the yeasts pure and don't fret about the
breed, exactly, because it's changing even as you watch it ...

This problem even effects the big brewers. I don't know how they do it ...
maybe they have cloned yeast cells frozen in vast amounts against future
mutations in their breeding stocks. But you can't stop Nature ...

I'm rather enthusiastic about breeding yeasts and trading them with friends,
as a local member of the Yeastie Beastie Preservation Society - which doesn't
exist, but may soon. (-:

- -- richard


=====
- -- richard childers rchilder@us.oracle.com 1 415 506 2411
oracle data center -- unix systems & network administration
... Minds are like parachutes ... they operate best when open.


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