Cold crash killed my yeast

[dlester]

I've been working on harvesting yeast, but it appears that when I cold crash beer to force the yeast to settle out, the yeast don't survive.

I am assuming from what I have read, yeast don't like extreme temperature changes? Has anyone else had this problem.


Cheers,

 

[helibrewer]

Temperatures above freezing should not kill yeast. Bottle conditioning after cold crashing is common practice. How are you determining that your yeast are dead?

 

[Yooper]

If the yeast isn't frozen, it isn't dead. What makes you say your yeast is dead?

 

[dlester]

I tried re-using the yeast, and nothing happened. I assumed dead.


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[Yooper]

I tried re-using the yeast, and nothing happened. I assumed dead.


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How old was it, and how much did you use? I have successfully used yeast in my fridge for months and months after saving it, but of course I used a small starter to get it going again.

When pitching fresh slurry (say, within a week of brewday), I check mrmalty.com's yeast pitching calculator to ensure I don't overpitch. I have a batch sitting here next to me using saved yeast from a week before and it started fermenting within 12 hours after pitching.

You still want to use a calculator, to make sure you don't underpitch or overpitch, but reusing yeast has saved me a ton of $$$$ just this year alone.

 

[AnOldUR]

Cold crashing before harvesting is a good way to help get some of the less flocculent yeast. As said, if you don't freeze them, they'll be fine as they are when you store a new pack or vial of yeast in a refrigerator.


edit:
My avatar is 10th generation harvested yeast.

 

[normzone]

Ah, I love you guys. This is EXACTLY the issue that made me sign in for the first time in months to research.

I've been burning my wallet up with storebought Pizza Port Mongo, so we finally re-opened the brewing pipeline this weekend.

We want to rinse-and-repeat with our yeast to keep costs down, and I'd experimented with saving the dropout from the cold crash, and waking it up with a starter as the most convenient method of re-using yeast.

It had worked for me in the past and I was wondering what the consensus was. Now I know.

Thanks again folks -
Norman aka normzone

 

[dlester]

Well, Ok I might have accidentally froze the yeast. I guess that's the answer.


Thank you for everyone's help,

 

[Yooper]

Well, Ok I might have accidentally froze the yeast. I guess that's the answer.


Thank you for everyone's help,

Yes, freezing will kill them. Well, that's not strictly correct. Freezing doesn't kill them- the thawing does.

When they thaw, the ice crystals in the yeast will rupture the yeast cells. If you want to get into yeast ranching, you can freeze yeast in agar, and then they will be fine.

 

[flars]

I've been working on harvesting yeast, but it appears that when I cold crash beer to force the yeast to settle out, the yeast don't survive.

I am assuming from what I have read, yeast don't like extreme temperature changes? Has anyone else had this problem.


Cheers,

Yeast, during fermentation, react negatively to sudden temperature changes. The yeast will recover, given sufficient time, to continue fermentation when the wort is warmed to the yeasts optimum fermentation temperature.
Cold crashing will not freeze the yeast unless the beer is frozen. Cold crashing will only cause the yeast to become dormant.
You will lose 10% viability for each freeze thaw cycle it the yeast is truly frozen.
Yeast harvested after cold crashing needs to be handled gently. Dumping the harvested yeast into a to hot starter wort of to high OG will further stress the yeast and cause more cell wall ruptures. Some yeast cells will survive, but the total number of viable cells has been reduced.
Give your starters time. Starter size should be at least 1 liter. OG of the starter should be less than 1.040. Your yeast will propagate new cells. A step up starter would most likely be needed if the harvested yeast has suffered multiple stresses.