Author Topic: Is Yeast Too Old?  (Read 774 times)

Offline Bitter Alchemist

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Is Yeast Too Old?
« on: April 12, 2017, 11:43:13 PM »
Normally I buy my yeast locally, but I could not find the San Francisco Lager yeast at LHBS.  I ordered WLP810 Online and it arrived with a date of 12/22/16... nearly 4 months old.  Is this typical?  The yeast I usually buy locally is 1-2 months old. 

According to the Brewers Friend calculator, the most yeast I can produce (using 2 packs) after 6 generations is 308 Billion.  This is well below my target pitching rate for the California Common I planned to brew.

Im sure the yeast will brew beer, but probably not to its full potential. Am I worrying too much about this?

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Re: Is Yeast Too Old?
« Reply #1 on: April 12, 2017, 11:46:09 PM »
Normally I buy my yeast locally, but I could not find the San Francisco Lager yeast at LHBS.  I ordered WLP810 Online and it arrived with a date of 12/22/16... nearly 4 months old.  Is this typical?  The yeast I usually buy locally is 1-2 months old. 

According to the Brewers Friend calculator, the most yeast I can produce (using 2 packs) after 6 generations is 308 Billion.  This is well below my target pitching rate for the California Common I planned to brew.

Im sure the yeast will brew beer, but probably not to its full potential. Am I worrying too much about this?

Yeah, I think you are.  If it was me, I'd do a one qt. SNS starter and call it good.
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Offline a10t2

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Re: Is Yeast Too Old?
« Reply #2 on: April 13, 2017, 12:02:09 AM »
According to the Brewers Friend calculator, the most yeast I can produce (using 2 packs) after 6 generations is 308 Billion.

That doesn't sound right. As a rough rule of thumb, each liter of starter wort will result in 50-150 billion new cells, depending mostly on access to oxygen.
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Offline Bitter Alchemist

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Re: Is Yeast Too Old?
« Reply #3 on: April 13, 2017, 12:14:50 AM »
According to the Brewers Friend calculator, the most yeast I can produce (using 2 packs) after 6 generations is 308 Billion.

That doesn't sound right. As a rough rule of thumb, each liter of starter wort will result in 50-150 billion new cells, depending mostly on access to oxygen.

According to White Labs you lose 0.7% Viability every day. Two packs give you 200 Billion cells, but that is on the day they are produced. At 111 days you're left with only 44 Billion cells.

I thought the maximum growth factor for a starter was 6.  Therefore, the most cells you can produce are 308 Billion regardless of starter size?

Offline a10t2

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Re: Is Yeast Too Old?
« Reply #4 on: April 13, 2017, 12:28:50 AM »
I thought the maximum growth factor for a starter was 6.  Therefore, the most cells you can produce are 308 Billion regardless of starter size?

That makes no sense to me, and it isn't what my data suggest. Yeast reproduce until they run out of food, assuming nothing else stops them. Most of my propagations start with <20 billion cells and average ~120 billion per liter final cell count.
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Offline tommymorris

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Re: Is Yeast Too Old?
« Reply #5 on: April 13, 2017, 12:54:00 AM »
I think if you make a 1Q SNS starter like Denny suggests and you get a krausen the next day you are good.  If after 24 hours you don't see any signs of life you may want to report back.

My experience is yeast  lasts a lot longer than calculators predict.

Offline el_capitan

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Re: Is Yeast Too Old?
« Reply #6 on: April 13, 2017, 02:51:20 AM »
I think if you make a 1Q SNS starter like Denny suggests and you get a krausen the next day you are good.  If after 24 hours you don't see any signs of life you may want to report back.

My experience is yeast  lasts a lot longer than calculators predict.

I second that!  Yeast are pretty resilient. 

Offline Todd H.

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Re: Is Yeast Too Old?
« Reply #7 on: April 13, 2017, 02:06:53 PM »


That doesn't sound right. As a rough rule of thumb, each liter of starter wort will result in 50-150 billion new cells, depending mostly on access to oxygen.
[/quote]

a10t2 is right.  A yeast culture will saturate at around 10^8 cells/ml (aka 100 billion cells per liter).  It really shouldn't matter that you're "only" putting in 44 billion cells... they'll double twice and that's likely it, assuming a 1L starter.  (Source, just in case you care: my PhD was in a yeast genetics lab... did more cell counting than I care to remember)
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