Subject: yeast culturing
Date: 1989-08-02 13:33:00 GMT
I thought that I might share my yeast cultivation methods with you.
I am a microbiologist by training and have been culturing my own
yeast for about 1 year. There is no question that liquid yeasts
improve the quality of your homebrew.
To use use liquid yeast properly, you should first prepare the
starter medium. By far the easiest thing to do is to set aside one
or two quarts of wort every time you brew. While the wort is still
very hot, transfer to a suitable sanitized container and place in
the refrigerator until you are ready to use it. I usually make and
can wort for this purpose. I boil 1 can (3.3 lb) of M/F light
extract in 4 gallons of water with 0.5 oz of hops for 30 minutes.
I then transfer the wort to clean 1 quart canning jars, put on
canning lids, and can in boiling water for 15 minutes. Now I have
yeast starter medium whenever I need it.
To begin a yeast culture, transfer 1 qt of starter to a
sanitized 1 gallon jug (the kind that cider comes in) and put a
stopper on it with a fermentation lock. (The common jug takes a #6
or 8 stopper, I think). Transfer aseptically 30-40 mls of the
yeast stock culture (this is one Wyeast liquid culture that has
been previously started in the manner described by the
manufacturer) to the 1 quart of wort. Place the jug in a warm dark
place. These cultures are usually ready to use 18-24 hours later.
With regard to pitching rates, professional brewers pitch enough
yeast to reach a final concentration of about 10 million cells per
ml. The relationship is about 1:10 (1 part of starter for 10 parts
of wort). You will need 1 qt of starter/5 gallons of ale wort or
2 quarts of starter/5 gallons of lager wort. I always get a nice
cover on my fermentations within 18-24 hours (not days) using this
If you want to prepare a number of stock cultures for future
use, pour about 1/4 cup of yeast into sanitized 1 pt containers
(with lids, not locks). Add about 10 ml (this is about 2-3
tablespoons I think) of sanitized glycerin or glycerol USP grade.
To sanitize the glcerine before use, put the glycerine in a heat-
resistent (pyrex) jar or container (canning jar?) and put in a
boiling water bath for 20 minutes. Let cool before use (Put the
lid on loosely or you will never get it off). Freeze the yeast
culture quickly. Concentrations (v/v) of glycerine 10-20% will
preserve your yeast cultures frozen for 6 months to 2 years
depending upon your conditions. To use frozen cultures, thaw
quickly and set in a warm place for a couple of hours. If you you
do not sense that the culture is completely active (by the release
of gas when you crack the lid), you can activate the culture by
puting in an equal volume of wort, mixing and continuing the
incubation until you detect yeast activity. Do not use any yeast
culture that has a sour smell. An active yeast culture should
smell fruity (like green apples).
To Florian Bell: Hey Flo...Did I hear you correctly when you said
that the temperature in your neighborhood is in the high sixties
MOST of the year. Are you talking daytime temperatures? How cold
Any folks that have any questions concerning yeast culturing can
contact me at 1-202-576-3012 (0730-1630 Eastern) or 1-301-869-0894
(1730-2100 Eastern), or send me an E-mail.
Erik A. Henchal
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