How hot can liquid yeast survive?

I have an order coming in today from AHS, and in this part of Cali we're currently experiencing some hotter than normal weather, which makes me wonder how hot that liquid yeast can survive in those UPS trucks? Has anyone ever received dead yeast ordering online simply due to the heat experienced during shipment? I ordered it with an ice pack, but I doubt that'd help it much beyond 24 hours.

I'm definitely planning on making a starter for this batch, but having never done one before, I'm wondering- should I use the DME from the kit? I have no precise way of measuring out how much to put in, and by precise I mean a scale. I'm thinking of going and getting something pre-measured from the LHBS to use with my starter. What you guys think?

I thought they died around 120-125* or so. Hopefully someone can answer more definitively for you...

At low temperatures (0-10 C) yeast will not grow, but not die either. At temperatures 10-37 C yeast will grow and multiply, faster at higher temperatures with an optimal growth at 30 or 37 C (that depends on the species). At higher temperature the cells become stressed, meaning that their content becomes damaged and which can be repaired to some degree. At high temperatures (>50 C) the cells die.

If you make a starter for a liquid yeast that has been overheated then cells that lived can make more cells and bring it back to strength. You should see activity in the flask or container for ales and to a lesser degree for Lager yeasts. If you get good activity then it is OK.

It depends on the strain, but it's very difficult to kill all of the yeast - a starter will usually bring even the most abused vials and smack packs back to life.

i'm headed out of town this weekend and i'm leaving when i get off work tonight at 5.


i received my order wednesday and immediately brewed my bavarian dunkelweizen from AHS. Right now it feels like this entire country is experiencing a heat wave and my box was delivered to me feeling a bit hot. the yeast came to me with a melted ice pack.

i was impulsive and did not make a starter before i pitched the yeast. i'm pretty sure the yeast is dead. the problem is i can't wait out the full 36-72 hours because i'm leaving in like 10 hours.

i just said forget it and i pitched some nottingham dry yeast. hopefully things work out alright...

Goatey said:

i just said forget it and i pitched some nottingham dry yeast. hopefully things work out alright...

Click to expand...

Their "the backup plan" advertisement is sure a damn good one.

I ordered from the Flanders brown from them about a month and a half ago. Yes, mid July from Texas to Georgia.... the entire box was warm to the touch when UPS handed it to me. Hoped for the best and pitched the yeast with out a starter and off it went after about 48 hours.
Now I dont plan on doing that again. Going to start buying any liquid yeast locally from here on it. But it didnt seem to kill enough of them to make a difference.

I got a dead yeast pack from AHS a while back.. I called them up, and after a bit of trouble shooting/ arguing ("yes, i made a starter over 36 hours ago", "yes, i cooled my wort first", etc) they gave me a credit for the yeast (not for the ice pack though).

I would recommend getting yeast locally, at least during the summer (and in my case the winter as well).