Subject: RE: Homebrew Digest for December 20, 1988
Date: 1988-12-21 13:45:00 GMT
SUBJECT: FREEZING YEAST CELLS
There really is no mystery about "freeze-shield" agents. There
are two commonly used cryoprotective agents used in microbiology:
DMSO and glycerol. DMSO is used at a final concentration of 10%,
and can be used fresh out of the reagent bottle since this agent
is self sanitizing. Glycerol is used at a final concentration of
50%. You must sterilize glycerol before use in a pressure
cooker, or at least sanitize it. You can sanitize it by placing
the glycerol in a pint mason jar and placing the jar in a boiling
water bath for at least 20 minutes. Most folks don't like to use
DMSO because of the smell. I think that you can get glycerol at
the drug store...but it must not contain any adjuncts or
perfumes..ask for the USP grade from the pharmacist.
Some other suggestions: Freeze only small aliquots. Once you
have added the cryoprotective agent, place the yeast in the
freezer immediately. When you are ready to use the frozen stock,
warm it to room temperature quickly. Transfer cells out of the
freezer quickly to fresh wort.
I hope that this is helpful.
Erik A. Henchal
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