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yeast ranching for the Junior Scientist in all of us

yeast slants

Is this your first culture? If so, read this note about care and feeding...

Yeast culturing is cool because it's where you get to pretend to be a microbiologist, use neat gear, and save about a ton of money on liquid yeast.

Yeast cultures can be done in slants (ie, test tubes leaned so the media congeals at an angle or "slant"), in petri dishes, or frozen in specially prepared anti-icing media. I use the slant method.

Yeast culturing is not particularly difficult but it does require a bit of time, some extra pieces of hardware and sterilization (not sanitation) that you don't often use in homebrewing. Planning ahead can greatly reduce the time factor. Basically you make some media for the yeast to live on, inoculate the media with the yeast, then later on you inoculate your starter with the cultured yeast and pitch when ready.

my yeast ranch

Culture-al history, hahaha!

some methods I am testing

The main problem I am experiencing is water condensation (presumably from the agar) in the tubes. From best to worse so far:

Sterile Instruments, Flamed Bottle method=Sterilize 50ml flash, funnel, and noc loop in pressure cooker. Decant bottle off sediment. Flame lip of bottle. Pour dregs into flask. Inoculate media from flask.
DW=5ml of Distilled Water pressure cooked 15psi/15min and cooled. Blob dropped in from a loop, close cap, shake vigorously. Store at room temperature. This method requires plating before building back up into a starter. Based on an archive in the March/April 1997 Brewing Techniques magazine article A Simple, Practical Method for Long_Term Storage of Yeast, by Michael D. Graham.
SITCap=Sterilized In Tube, cap in place: agar poured into tubes, caps screwed on but not tight.. Pressure cooked 15psi/15min cooled in closed cooker overnight. Close caps when condensation is gone.
SITC=Sterilized In Tube: agar poured into tubes, tops stuffed with cotton ball. Pressure cooked 15psi/15min with "canned" stoppers, cooled in closed cooker overnight. Note: pulling the cotton out results in wispy attachments. Twisting the cotton before removal greatly reduces this problem.
HAP=Hot Agar Pour: agar and tubes sterilized 15psi/15min, agar cooled somewhat, poured into tubes and cooled.
SIT=Sterilized In Tube: agar poured into tubes, loosely capped. Pressure cooked 15psi/15min, cooled in closed cooker overnight..
SIOT=Sterilized In Open Tube: agar poured into open tubes, caps separate in pressure cooker. Pressure cooked 15psi/15min, cooled closed cooker overnight. Caps placed on when cool.

further study

  1. braukaiser's tutorial
  2. Dr. Raines' guide to starters/cultures
  3. My blog entry on distilled water cell storage
  4. HBT Wiki article on slants
  5. Mike Sims' Yeast Slants page
  6. HBT Yeast Washing Illustrated (ie, yeast cake decanting)
  7. Liddil.com yeast culturing site, although I disagree with the "say no to Wyeast" tagline. The commercial yeast companies are an important part of the homebrewing scene.
  8. Yeast Culturing youtube vid
  9. Yeast Culturing youtube vid
  10. Yeast Culturing youtube vid


I buy much of my lab gear from Basic Science Supplies.

$Id: yeast.orb,v 1.29 2009/12/15 02:49:52 mouse Exp $

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