Bruiz54

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So last night I tried to make a frozen yeast bank. I had small 15ml tubes that I filled 1/2 with yeast 1/4 with sterile water and 1/4 with Glycerine. I put it in the freezer and it froze! My understanding was that the Glycerine was suppose to make it so that the yeast would not freeze. Is this true or will it freeze and not puncture cell walls. Got any advice? Thanks

Revvy

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My understanding is that the glycerine prevents the explosion of the cell walls...NOT the yeast bank from freezing...It is called a FROZEN yeast bank afterall!

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Chriso

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Yep! Everything is as it should be, no worries mate.

Did you read the bit about a defrosting freezer? If you have one, you should invest in a small cooler and some ice packs to line the sides with. The Defrost cycle on the average-Joe freezer will kill your yeast.

Congrats on building your bank up!

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Bruiz54

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See here is where I am confused "Yeast can recover from sub-zero temperatures, but frozen water can kill them. Frozen water crystallizes and can puncture yeast cell walls, but two things can be done to prevent this. First, use a small volume of water (hence the small vials) and leave a bit of room for expansion. Second, a bit of glycerine, also known as glycerol (but NOT glycol!!) helps prevent freeze damage." So frozen water kills them, but glycerine prevents freezze damage. So one sugests not to let anything freeze and the other suggest that it will be frozen, but the glycerine will prevent damage. So what is correct? Also have you had them frozen then maqde a starter that was ok?

Bruiz54

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Well i just stuck it in the freezer, hmmm my freezer will automatically defrost? I dunno its a pretty new fridge like 2 years old. Thanks for letting me know and I am looking forward to haveing diffrent starins on hand when I need them. LOL my mad science experiment grows all the time lol

jfrizzell

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They will be fine. The glycerin keeps crystals from forming which puncture the cell walls of the yeast. It still freezes.

Donasay

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any fridge built in the last 10 to 15 years has auto defrost, get a cooler.

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Bruiz54

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Darn, Ill have to buy another stupid cooler. So I just line it with cool gel packs that have been frozen that will keep it frozen?

Chriso

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Go back to the "Start your own Frozen Yeast Bank" thread and there's a picture somewhere inline in there that shows. But yep, a small-ish cooler with just enough room for your yeast bank, and the cool gel packs along the side.

I would re-read that thread in its entirety, a couple of times. I found, personally, there was SO much information there that it's taken a couple of re-visits to fully digest and understand.

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Bruiz54

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Thank you guys so much. Will do. It is gonna be nice to have a bank