Accidentally unfreezing yeast

[geobotsar]

I have been frrezing washed yeast with glycerin for a couple of years. Last week my freezer was accidentally turned off, and by the time i found out, the temp in the freezer was around refrigerator temps(maybe around 7 c), as also my stored yeast vials.
I imedieddly turned the freezer on. What i am wondering is, is it ok to use those yeast vials, or because they were unfrozen, and then frozen again, its most likely that the have turned bad.

 

[IslandLizard]

Those are the scenarios where a temperature monitor/alarm would come in damn handy.

I think you have to swirl them a few times during the refreezing process, like you would do normally, to keep the glycerine distributed.

I yield to more knowledgeable minds on survival rate.

 

[geobotsar]

Thanks, unfortunately i didnt think about swirling the vials before refreezing them, guess i will make a starter with one of the vials and see how it goes. For how long have you been keeping your yeast in the freezer? Is there a maximum amount of time?

 

[IslandLizard]

Strange no-one else chimed in on your questions.

It maybe just fine. The swirling is a bit of a mystery anyway, as the glycerin may separate out well before it gets solid enough. Haven't really tested that though. I've read a max of 1 year freezer storage is recommended before rewaking, regrowing, and refreezing, unless you can store them at much colder temps (far below -4°F - 0°F). -4°F may not really freeze them solid with the glycerin addition.

 

[PoppinCaps]

This exact thing happened to my stocks last month. I took that opportunity to regrow and make fresh stocks as they were 3+ years old. Mine were at room temp for at least 2 days in glycerol, but still came back strong, just needed a small stepper before an 800ml starter then aliquot and freeze again.

I would do the same if I were you, just to be sure they're fresh the next time you need them.

 

[geobotsar]

Thanks guys, i am impressed to hear that they can last 3 years in the freezer poppincaps.are you guys putting the vials in isopropyl alchohol, or just plastic containers?

 

[PoppinCaps]

I put the vials with liquid level submerged in alcohol for 24 hours to control freezing time, then move them to a styrofoam holder after that. The old stocks were in a styrofoam box with cold packs since it was a self-defrost freezer, but the new ones are just out in the open in a deep freezer.