How cold to kill yeast?

[Shred]

I recently brewed an IPA and pitched WLP001 (1 liter starter on stir plate into 1.068 wort).

I have plans to experiment with adding grapefruit juice when kegging. I'd also like to cold crash prior to dry hopping in an effort to prevent the yeast from pulling aroma out of the beer when it chills.

While I'm pretty certain I won't have much yeast activity at 38-40F, I want to know for sure I've killed my little buddies and they won't start munching on the fermentables in the juice.

Would the beer need to be frozen in order to accomplish this or is near freezing cold enough?

 

[JDGator]

that cold will not kill the yeast, it only slows them down.

You would need to add Campden tablets. i'm not a pro on this so hopefully someone else can chime in with a better answer.

 

[j1n]

The yeast will go into hibernation and it will stop the fermentation but it wont kill them. you have to freeze them to kill them cause the ice crystals puncture the cell walls and they die.

 

[Shred]

That's more or less what I thought. Should I worry about any fermentation activity over the course of 2 weeks or so at temps below 40F?

 

[Hello]

I think you'll be okay. It's an IPA so you'll likely drink it fresh. You're cold crashing then kegging and at that point you're adding the juice. There will be less yeast in suspension when you keg and add the juice. I think the yeast will lie fairly dormant and you won't see much of a difference while the beer is in the keg at 40F.