So I harvested my yeast for the first time (WLP566 Saison II), but I left the fridge temp mega low by mistake and it froze overnight. I have immediately thawed it out, but I am wondering if it now waste of jar space or could it still be viable?

2 Answers 2


The viability will have been seriously affected you may have some OK cells in there, but the formation of ice crystals with in the cells will have ruptured the majority of the cells. You may be able to make a starter from it.


Make a starter ASAP. That is the only way to know if anything survived. Chances are slim as the frozen cells rapture when frozen. If the starter picks up, then step it up and harvest from that.

If you want to freeze your yeast you need special "anti-freeze" so that the cells do not rapture.

  • 1
    The anti-freeze is 30% glycerine 70% water solution.
    – mdma
    Commented Jul 9, 2015 at 2:34

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