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Old 06-25-2012, 12:13 AM   #1
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Default Glycerin Stocks

There is a lot of info on making them but not about taking them out and stepping up the yeast to pitchable quantities. Does anyone have a solid method for pitching from glycerin stocks?

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Old 06-25-2012, 12:41 AM   #2
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I store my stocks in 2ml cryovials at -80c. When I want to grow stocks, I scrape a pipette tip worth of the solid into 3mls of 10% dry malt extract (100g/L) and shake at 30c/200rpm for 24-36h, basically until turbid. Then I inoculate 50mls of 10% DME at 18c/200rpm for 24h and then inoculate 1 to 4 L of 10%DME (depending on the target beer's OG) for another 24h at 18c for ales or 48h at 10c for large strains, again at 200 rpm on an incubated orbital shaker. If I'm in a hurry I centrifuge 6000xg for 10min, otherwise just crash cool and decant the bulk of the supernatant, leaving the yeast matter behind.

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Old 06-25-2012, 12:57 AM   #3
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At the risk of helping a Buckeye, with frozen stocks you want to chill them as gradually as you can, but thaw them quickly. I put mine in some ~75 degree water and kept replacing the water until it thawed. Then you want to be certain to star-san it really well on the outside. I pitched mine into a 250mL starter on a stir plate (my frozen vials are about 7mL of yeast solids). Then going forward I just estimate starter sizes and steps based on yeast volume and yeastcalc.com. Every one is going to be different, so there's really no use in trying to make a standard plan.

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Old 06-25-2012, 04:17 AM   #4
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My first time freezing I didn't do a great job. I got maybe half a ml of yeast in the vial. I recently pulled one out and just thawed it in my hands. I didn't take long to unfreeze. Tossed the yeast in a small amount of wort (maybe 200ml) and it was taking off within a few hours.

I'm obviously much less scientific than some of these folks.

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Old 06-25-2012, 01:03 PM   #5
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Very nice, thanks for the info.

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Old 06-26-2012, 05:46 AM   #6
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As said, you got to freeze them slowly and thaw quickly (best in 38°-40°C water).
I store my yeast in 125ml vials in 15% glycerin solution, depending on washing efficiency I got ~100B cells which gives me minimum 25B after thawing (according to one our friend who have done cell counting w/microscope viability is 25%).
Using yeastcalc.com I step it up to pitching rate, usually in 2-3 steps.

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Old 06-26-2012, 01:54 PM   #7
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Can anyone expand on slowly? The only thing I can think of it stepwise 4C frige, -20C fridge, then -80C. should this take a day? One cooling step / day? Thanks!

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Old 06-26-2012, 03:40 PM   #8
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I keep them 1 day in fridge and then they go in freezer, w/occasionally shake until they freeze solid.
It is best to use non-self-defrost freezer to avoid thawing circles.

You can find more about freezing here:
http://www.homebrewtalk.com/f163/do-...freeze-269488/

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Old 06-26-2012, 05:24 PM   #9
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I also went fridge for a few hours to chest freezer. Seemed to work ok.

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