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Old 08-23-2011, 02:04 PM   #1
superslomo
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Nov 2009
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The instructions in the wiki for making frozen yeast cultures is great stuff... this is referring of course to the glycering mixture process with test tubes.

However, instead of washing the yeast cake, is there any reason you couldn't just use the thick slurry in the bottom of a starter jar to produce the test tubes in this case? It would seem easier to maintain sterility, and easier to get a good hearty quantity of yeast that way.

Has anyone tried this? I'm thinking if you just take the 1st generation yeast that you've built up in a starter, and make four tubes out of it (for example) it would be a quicker process than washing/separating/pipetting/washing/separating/pipetting that is part of the wiki process.

 
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Old 08-23-2011, 02:17 PM   #2
Yooper
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I think you'd be getting more trub than yeast in that case.

I don't freeze yeast slants- but if I did.........here's what I'd do:

Flame the weast vial. Flame the loop. Pull out the sample(s) from the vial directly, and save it as slants in agar. Then use the remaining yeast in the vial as a starter.
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Old 08-23-2011, 02:57 PM   #3
superslomo
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Nov 2009
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Ah, not planning on doing slants, just glycerine stabilized frozen yeast cultures. Per this link to the wiki.

Someone mentioned that the sediment in the starter, once crashed, is basically all viable yeast, as opposed to the trub at the bottom of the fermenter after a month.

 
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Old 08-23-2011, 04:08 PM   #4
Sardoman
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I have a frozen yeast bank and I always make my frozens directly from the vial/smack pack. I want a high degree of confidence in the sterility of my frozen stocks and I want reasonably good viability.

I pour the vial/pack into a starter, then let the last few drops fall onto a wort agar plate. After a couple days of growth I scrape it off the plate and into vials of glycerin, and at the same time streak a wort agar plate just to make sure that I have a pure culture. If I were to see contamination I'd dump the glycerin stocks.

You could harvest the yeast from a starter as you suggest. This might be easier or more convenient than waiting until after your beer has fermented out to collect from the yeast cake. If your starters are well aerated then you will probably get better viability from harvesting at that stage. But sterility would be iffy. I would not harvest from a spent 5gal yeast cake without streaking to single colonies on a plate first because a finished batch, while quite sanitary, is definitely not sterile.

 
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