Freezing
Yeast
C.D. Pritchard - New,
2/2001
I tried slants for saving yeast.
They were a real PITA what with the periodic reculturing required (which
I forgot about more than once!) and the fairly anal sanitization that is
reportly required. Freezingis much easier and a lot less time consuming.
What I really likeis that I've stored yeast sucessfully for 2 years, 4
months so far.
I started with a kit called the "Yeast
Bank" (tm) made by CountryWines. It
contained several 10 cc plastic tubes with nice attached caps, a typical
plastic freezer container for holding them (the "Bank"-with a cute stick
on label even), an eyedropper, instructions, and most importantly, "Freeze
Shield" (tm). The later is a blue tinted, thickish liquid which the
mfg. recommends be kept frozen between uses. It maybe a glycerine
solution since folks have reported in the HBDigest that they've used
glycerine for freezing yeast. Info on ordering the Yeast Bank and Shield
are here.
The Basics from the
Manufacturer's Instructions:
-
Make a starter (how I prepare them is here)
and pitch it with yeast.
-
When fermenting strongly, swirl to suspend
the yeast and then fill tube(s) to about 1/2" from top with starter solution.
The caps on the tubes have two positions- full down and partially down.
Cap in the partially down position and place the tube(s) up-right in a
fridge. The remaining starter can be used for pitching into a brew.
-
The next day, sanitize the eyedropper and
draw off the liquid above the settled yeast. Fill the tube (with
yeast in the bottom) about 3/4 full of thawed Freeze Shield. Cap
tightly, shake and place upright in a cup with tissue in it (to slow freezing).
Place cup/tube(s) in the coldest part of your freezer. Record yeast
variety, the date and, if applicable, the number of times the yeast has
been recycled.
-
The next day, quickly reseat the tube caps
if they've sprung up. Can store the yeast so frozen for
"many months". Put in a container padded inside with tissue paper
if you store them in a frost-free freezer. Also, do not let the tubes
thaw prematurely (e.g., while you're defrosting the freezer).
-
To use, make a ~ 1 pint starter then thaw
the tube in luke-warm waterand pitch into starter just as soon as
it's thawed.
I frequently let the starter go to completion
then use an Iodophor sanitized syringe fitted with a long, large ID needle
(made from 1/16" ID copper tubing heated and jambed into the end of the
syringe) to draw off yeast sediment from the starter and dispense ~ 2 cc
into each tube. Done this way, they can go straight into the freezer
after the Freeze Shield is added and they are shaken.
If the Country Wines instructions are followed,
much yeast will settle before the solution freezes. To see if this
was a bad thing, I tried placing a tube into a qt. container of a propylene
glycol/water solution that had been in the freezer several days.
Not much yeast settled out but performance wise, I couldn't tell
any difference betweenthe two methods. One day, I hope to try a side-by-side
experiment. Similiarly, I've done a few tubes with 1/2 of the
recommended Freeze Shieldand haven't noticed any problems.
The tubes and caps that come with the Yeast
Bank are really nice bu tI've used plain plastic culture tubes with screw
tops with good results. I've also frozen harvested yeast from the primary
dregs with good results, but I think this is tempting faith.
After the yeast is frozen, I put them into
a zip-lock bag on which the data on the yeast has been written with a Sharpie.
Sourceof
the Yeast Bank and Freeze Shield
Country
Wines themanufacturers the Yeast Bank and Freeze Shield.
I can't find either on their web site, so, here's the poop as of Feb. 2001:
Catalog item 1800 Yeast Bank $5.95
2 lb. shipping weight
<---- A real steal IMHO
Catalog Item 1801 Freeze Shield $1.95
7 oz. shipping weight
Catalog Item 1802 Extra Freezing Tube
$ .55 1 oz. shipping weight
3333 Babcock Blvd. Suite 2
Pittsburgh, PA 15237-2421
Phone: 412-366-0151
FAX: 412-366-9809
info@countrywines.com
Questions or comments? Email
me.
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