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CDS

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I'm doing a 5.5 gallon batch of Oatmeal Stout this weekend. The recipe recommended Wyeast London Ale III, so I have a pack waiting in the fridge. I've never pitched liquid yeast before, and I have a couple concerns/questions.

The OG of the stout is 1.047. The instructions say one package will be sufficient for up to 5 gallons. Since I'm actually doing 5.5 gallons, I punched in the numbers on Brewfather, and the resulting recommendation is 182 Billion cells will be required to do the job (1 pack of Wyeast contains 100 Billion). Even worse, using Brewfathers Yeast Viability calculator indicates that only 5% of the yeast in this packet would be viable (manufactured June 4, 2020.

Questions:
1) Am I better off just pitching TWO packages (i.e.: 200 billion cells)? How precise does this need to be?
2) Any experienced users of Wyeast and/or Brewfather - how accurate are those viability calculations? Does Wyeast really degrade to that degree (Wyeast advises using it within 6 months)?
 

McKnuckle

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If you pitch two packs of yeast manufactured five months ago, that's only marginally better than one. Your better option, short of obtaining some recently packaged yeast, is to make a starter, assuming you have some DME on hand. Since today is Tuesday, you have just enough time to get one going, have it finish, then put it in the fridge so the yeast can drop out.

The Brewer's Friend yeast calculator thinks you have zero viability. So it could be worse. :) In reality, there are likely some cells in there. But it's not a slam dunk, and you could be frustrated. I recently pitched a package of Wyeast 1469 dated six months ago, and it literally did nothing. I had to pitch another yeast to save my batch.
 

Alex4mula

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I bet you will be more than fine. What I don’t like about it is that the internal yeast nutrition package is very hard to break. I just pitched one on a pilsner this weekend and it started in just 4hrs. Expiration was Jan 2021. No starter.
 
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Dgallo

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You should make a starter. A Healthy fermentation is the most critical step in making good beer. Very simple to do. Boil a liter of water and use a 1/2 cup of dme. Cool to pitching temps, pitch the pack and let go for 24/48 hours and then pitch it into the beer.
 
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jddevinn

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To check the Brew father estimates, the typical pitch rate is calculated as

Ales Yeast Cells Required = (0.75 million) X (milliliters of wort) X (degrees Plato of the wort)
Lagers = (1.5 million) X (milliliters of wort) X (degrees Plato of the wort)

That would be 282 billion cells required.

Quite a different models for viability. I get 33% from 6/4/20 to today.

That would be about a 1.25L 1.037 SG starter on a stir plate
Or
A 1.25L followed by a 3L 1.037 SG starter with no agitation.

Of course all estimates. I would do a starter for best results.
 
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CDS

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I bet you will be more than fine. What I don’t like about it is that the internal yeast nutrition package is very hard to break. I just pitched one on a pilsner this weekend and it started in just 4hrs. Expiration was Jan 2021. No starter.
Thanks for the reply. Just an FYI - I found out that Wyeast very recently changed their packaging from displaying the "Manufacture Date" to "Best if Used by" date. I guess I got the older packaging.
 
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CDS

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You should make a starter. A Healthy fermentation is the most critical step in making good beer. Very simple to do. Boil a liter of water and use a 1/2 cup of dme. Cool to pitching temps, pitch the pack and let go for 24/48 hours and then pitch it into the beer.
Thanks! Sounds dead simple. Will the yeast eventually settle to the bottom so you can drain off excess liquid? I assume you don't pitch the entire litre into the wort...?
 

VikeMan

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Thanks! Sounds dead simple. Will the yeast eventually settle to the bottom so you can drain off excess liquid? I assume you don't pitch the entire litre into the wort...?
Some people pitch the whole thing. Some cold crash and decant. I prefer the latter.
 
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CDS

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To check the Brew father estimates, the typical pitch rate is calculated as

Ales Yeast Cells Required = (0.75 million) X (milliliters of wort) X (degrees Plato of the wort)
Lagers = (1.5 million) X (milliliters of wort) X (degrees Plato of the wort)

That would be 282 billion cells required.

Quite a different models for viability. I get 33% from 6/4/20 to today.

That would be about a 1.25L 1.037 SG starter on a stir plate
Or
A 1.25L followed by a 3L 1.037 SG starter with no agitation.

Of course all estimates. I would do a starter for best results.
Thanks! Just a related note: While searching around for more info in the forums here, I came across something I found interesting re: viability calculators - Wyeast advises to totally disregard them. There was a response from a Wyeast rep stating:
"We are familiar with the homebrew calculators that factor in the manufacturing dates, but these do not correctly reflect the quality of our yeast. Because many if not all are based on other suppliers’ information, and were not consulted or developed with Wyeast, I would like to offer the assurance that our yeast products will perform reliably following our product instructions and guarantee. When viability is incorrectly factored in and a larger than needed started is made, you can end up with too much yeast growth, too rapid of a fermentation, and negative influences on your beer."
 

Dgallo

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Thanks! Sounds dead simple. Will the yeast eventually settle to the bottom so you can drain off excess liquid? I assume you don't pitch the entire litre into the wort...?
You can certainly decant off the starter. To do this stick your starter into the fridge in the coldest spot but not to where it will freeze. Let it sit there for about 36 hours and then pour off about 2/3 of the liquid. It will only be about 1/75 of your entire beer volume at that point and will help you swirl the flocced yeast of the bottom of the container
 
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VikeMan

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Thanks! Just a related note: While searching around for more info in the forums here, I came across something I found interesting re: viability calculators - Wyeast advises to totally disregard them. There was a response from a Wyeast rep stating:
"We are familiar with the homebrew calculators that factor in the manufacturing dates, but these do not correctly reflect the quality of our yeast. Because many if not all are based on other suppliers’ information, and were not consulted or developed with Wyeast, I would like to offer the assurance that our yeast products will perform reliably following our product instructions and guarantee. When viability is incorrectly factored in and a larger than needed started is made, you can end up with too much yeast growth, too rapid of a fermentation, and negative influences on your beer."
There's virtually no way, using defaults in any of the popular calculators, to make so much yeast that it has "negative influences on your beer," regardless of how low a viability is assumed, i.e. that the "quality of our yeast" is ignored. Anyone who understands inoculation and growth rates would know that. Whoever at Wyeast wrote that paragraph should know better.
 
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jddevinn

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Unless you want to get equipment to count yeast cells in a sample and extrapolate total yeast count you have to trust someone. Yeast vitality calculators use estimates measured from different sources. The 33% I quoted above is based on 20% loss per month, stated by White Labs and verified as a good estimate for some calculators.

I'll admit that I overbuild starters and then reuse yeast for several generations. If the way Wyeast packs allows for a higher vitality then simple storage then I overpitch the first generation but not the subsequent ones.

Underpitching is worse than overpitching. Underpitching certain styles and yeast have greater effects then others.

I tend to try to do everything reasonable to get the best quality results. I find that starters, even multi stage starters, are reasonable for me.
 
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mannye

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I can only tell you my own experience. I had a kit that was way out of date and a Wyeast smak pak that was similarly passed its “use by” date.

I smacked the pak and it took a little longer to swell up than usual, but it did and I pitched it into the very out of date beer kit. This was a very long time ago and I believe it was a Pilsner kit.

it turned out fine. I kNow it’s not the same investment in time and money compared to making an all-grain oatmeal stout, but sometimes we worry so much about these things we take the fun out of it.

if you are truly worried, get a fresh smack pack and go from there. Maybe save the old one for something less expensive?
 
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