White Labs vial froze solid = dead yeast?

[kombat]

Yesterday I received a delivery from a mail-order Homebrew shop I use. However, the package was delivered during the day, and I didn't get home until suppertime. The temperature here yesterday was -13° F. When I opened the box, the vial of White Labs yeast (WL007 Dry English Ale) was frozen solid. I put it in my refrigerator to slowly thaw it back out.

My question is: Will having been frozen dramatically adversely affect the yeast's viability? Of course I'll still do a starter anyway, but how well do yeast typically survive being frozen in the vial like this?

 

[flars]

Chris White of White Labs had said freezing of the yeast in shipping may reduce viability by 10% due to some cells being killed.

 

[ram5ey]

Chris White of White Labs had said freezing of the yeast in shipping may reduce viability by 10% due to some cells being killed.

This exactly. Make a starter.

 

[IvanTheTerribrew]

Freezing damages/burst the yeast cell walls, the reason dry yeast can be out in the freezer is because of exactly that, it's dry. Think about if you put a glass container filled with water I'm the freezer, the ice will expand and break the container. I imagine it's the same thing with the yeast cells. I would consider making a simple starter, then if it shows activity I would wash it and that way you'll have a slurry of healthier yeast.

 

[roundhoundbrewing]

Make a starter. Even if it truely is only a 10% viability drop, you can't be sure if the vial froze and thawed a few times.

 

[ram5ey]

And the 10% rule applies to each cycle of freezing and thawing. So you have to keep that in mind.