Ice crystals in yeast packet

[twbalding]

I'm planning to brew a NB dry Irish stout extract next weekend but the yeast pack I bought has been in the fridge for a week and there are some ice crystals that formed in it. Is it ruined or should I still try to make a starter? I just got the equipment for a started but have not done one yet. I also have a chinook IPA in secondary that I could try and harvest yeast from but it's wyeast northern ale... not like the 1084 Irish ale I'm supposed to use.
Any thoughts on this?

 

[Qhrumphf]

Hmmm...I've never had that happen. I'd say there's probably some viability loss, but if you make a starter you would probably still be good to go.

 

[KurtB]

With a starting gravity of 1.042 a starter may not be completely necessary, but I would make one. If there is ever a question about the quality of yeast you are going to pitch, making a starter is the best way to make sure it is viable.

 

[Calder]

I don't know what to say. You will need to make a starter to see if there is any viable yeast in there as much of it will be dead. If liquid yeast freezes, the water in the yeast cells forms crystals that rupture the cell walls and kill the yeast.

Fortunately, if some of the yeast is alive, you will be able to build up the population relatively quickly.