Dry Yeast in freezer

[topfuelbt]

Last night when I got home from Brew Store I through a packet of Safale US-05 in the freezer with my hops is it dead.

[spiderwrangler]

It's 'probably' ok. Only one way to know for sure, but dry yeast shouldn't be affected by freezing, baker's yeast is commonly stored in the freezer.

[brewinhard]

I believe the process of making the yeast involves freeze dry packaging, although I could be wrong. As spider said, the yeast probably is not dead, but you might have lost some viability of the cells. Good thing is it wasnt in the freezer for an extended period of time. Those dry yeast packages have tons of yeast in them too, so at least some will wake up and be okay I am sure.

[Ozwald]

Yup, the drying process is similar to flash freezing, like the bag of individually frozen chicken breasts found in almost every supermarket. The problem with freezing anything with a cellular structure is water. It turns to ice crystals & the sharp edges will destroy cells. Flash freezing is much more gentle on cell walls. An unopened package of dry yeast has already been through the process & contains next to no water. I wouldn't even expect much of a drop in cell viability although I've not personally tried it & examined the results. I would allow the yeast to return to room temp before rehydrating to prevent unnecessary temp shock. If you're really worried about it, you could also do a small starter after rehydrating.

[topfuelbt]

Thanks for info everyone.