Author Topic: Old yeast slurry  (Read 1128 times)

Offline bboy9000

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Old yeast slurry
« on: February 18, 2015, 04:37:56 AM »
I have 800mL of thick yeast slurry that went from the fermentor from a 1.060 OG beer into sanitized mason jars the have now been in the fridge for nine months.  Mr. Malty shows I need 550-610mL of this to pitch into a 1.058 wort.  Would you recommend pitching the slurry? Would you recommend I do a starter with part of the slurry?  Do you think should just do a starter from fresh yeast? The slurry is Pacman I harvested from a few Rogue bombers and stepped twice then fermented a 1.060 wort with.

Edit:  The original beer from which  I harvested the yeast had an OG of 1.068.
« Last Edit: February 18, 2015, 04:47:03 AM by bboy9000 »
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Offline mainebrewer

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Re: Old yeast slurry
« Reply #1 on: February 18, 2015, 11:33:23 AM »
Does the yeast smell OK?
If it does, I would use a table spoon of it and make a starter.
Using Mr. Malty to determine starter size use a production date that matches the age of the yeast to see what size starter is recommended.
This should get you in the ballpark, you can adjust up or down based on your past experience.
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Offline leejoreilly

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Re: Old yeast slurry
« Reply #2 on: February 18, 2015, 02:57:42 PM »
I had some Vermont IPA yeast that I harvested from a batch of 1.080 FG IIPA about seven months ago. I wasn't too confident that it was still viable, but I wanted to use that particular yeast in a smaller (1.060) IPA this week. So I made a starter Sunday, got a nice krausen by Monday, crashed it and pitched it yesterday, and it was bubbling happily within about eight hours.

I did give the sample and the starter a serious sniff test, and I had some freshly harvested 1056 standing by just in case. But it seems to have come through OK. The proof will be in the tasting.

Offline Joe Sr.

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Re: Old yeast slurry
« Reply #3 on: February 18, 2015, 04:01:22 PM »
I store my slurries the same way as you have described.  Make a starter and you should be fine.  This is my standard MO.  I have two batches fermenting right now with yeast from old slurries.

I wouldn't pitch the whole slurry and hope for the best.  I think that is less likely to be successful.
It's all in the reflexes. - Jack Burton

Offline bboy9000

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Old yeast slurry
« Reply #4 on: February 19, 2015, 12:08:10 AM »
I store my slurries the same way as you have described.  Make a starter and you should be fine. 
How much of the slurry would you put into a 2L starter?  I have almost a liter of slurry.   Edit:  should I pitch just 100mL of slurry into the starter or the whole 800ml?  Remember it's 9 months old.
« Last Edit: February 19, 2015, 01:47:29 AM by bboy9000 »
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Offline Joe Sr.

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Re: Old yeast slurry
« Reply #5 on: February 19, 2015, 03:18:13 AM »
I think 100ml would be more than enough.  You might could go with a little bit more for a 2L starter, but I certainly wouldn't do the entire 800ml.

There are other threads where people get deeper into the right amount of cells to pitch in order to have optimal growth, but in my experience 100ml should be fine.  You want to grow new yeast, not just wake up the slurry.
It's all in the reflexes. - Jack Burton

Offline bboy9000

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Old yeast slurry
« Reply #6 on: February 19, 2015, 03:38:43 AM »
Thanks.  I did find a thread where somebody used 2 year old yeast.
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Re: Old yeast slurry
« Reply #7 on: February 19, 2015, 04:08:19 AM »
I like to separate the break and dead yeast cells from the viable cells when using an old slurry.  I wait until the starter hits high krausen before swirling, allowing the starter to settle for a few minutes, and then carefully decanting the liquid fraction into a sanitized container.  You can crash cool the liquid fraction or pitch it directly.     

Offline bboy9000

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Re: Old yeast slurry
« Reply #8 on: February 19, 2015, 04:11:13 AM »
Thanks for the tip.  Dead yeast was definitely a concern I had.  Do you think one starter is enough or will it need stepped up?
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Re: Old yeast slurry
« Reply #9 on: February 19, 2015, 02:49:38 PM »
If the starter is well aerated, 1L that is pitched at high krausen will be enough (i.e., a non-oxygenated stirred starter is not well aerated). The viable cells are in suspension at high krausen.  Carefully decanting the liquid fraction into a sanitized container at high krausen will give you the opportunity to cold crash the viable cells that are in suspension without having to worry about pitching a large number of dead cells and decayed organic matter. 

I have been using this technique to separate the viable cells from the dead cells and break material for a very long time.  In fact, I used it last weekend to separate the viable cells from the dead cells and break material from a two-month-old Saccharomyces cerevisiae crop last weekend.  The 600ml starter made from that crop was pitched into 3.5 gallons of wort on Saturday at 5:00 pm.  The yeast was fermenting strongly with a 1" head by the time that I checked on it at 6:30 am on Sunday morning.  My basement was at 56F due to the cold snap; therefore, I was quite surprised to discover that fermentation was well underway.