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Old 11-09-2013, 07:28 PM   #1
mattrennert
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Default Viability of Frozen Yeast

Anyone have a rule of thumb for viability of frozen yeast? I have heard 5% drop per week for active yeast, I would imagine freezing slows the degradation..

Maybe 2% loss per week is reasonable?

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Old 11-10-2013, 01:32 AM   #2
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Dry or liquid?

For liquid, freezing will kill the yeast. The ice crystals pierce the cell walls of the yeast. You would be lucky for any to survive unless you used a glycerin solution.

For dry - it will last for years. Dry looses about 4% per year at fridge temperatures, so would tale 10 years to be about 50% viability.

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Old 11-10-2013, 02:43 AM   #3
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To be more clear...
I'm wondering about viabilty of frozen yeast yeast slurry in a solution with 15% glycerine, stored in a non-frost free freezer.

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Old 11-10-2013, 02:48 AM   #4
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I don't know about the degradation, but I make vials with 5 ml yeast, 5 ml glycerin and 10 ml water. I resurrected a vial that a couple weeks ago had been frozen since 11/11.

I start with a weak 250 ml starter then step it up a couple more times. The 11/11 one started fermentation within 6 hours.

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