Splitting Yeast Packs - Home Brew Forums

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09-07-2011, 04:42 PM   #1
huge1s
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Jul 2011
Monument, CO
Posts: 238
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I would like to take a smack pack, split it into two and save the other for a batch to be made later (at which time...would like to split it again). Here is my plan:

-make a 1 liter starter
-split into two
-with one of the 1/2 liters, cool, decant and make another 1 liter starter to pitch
-with the other 1/2 liter, decant and save for the next batch.

my questions are:
1) is 1 liter enough to split into two?
2) will a 1 liter starter result in double the amount of yeast?
3) can I decant enough to use a white labs vial to store the yeast that I plan to save for the next batch, or should I find a mason jar or similar?

09-07-2011, 06:20 PM   #2
BBL_Brewer

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Feb 2011
Kokomo, IN
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Quote:
 Originally Posted by huge1s my questions are: 1) is 1 liter enough to split into two? 2) will a 1 liter starter result in double the amount of yeast? 3) can I decant enough to use a white labs vial to store the yeast that I plan to save for the next batch, or should I find a mason jar or similar?

Well it depends. I use the Wyeast pitching rate calculator to figure out such things. http://www.wyeastlab.com/hb_pitchrate.cfm A lot of people use Mr. Malty. http://www.mrmalty.com/calc/calc.html

Questions 1 & 2. Depends on whether you use a stir plate or not and what the original gravity of the wort will be. The recommended pitching rate for ales is .75 million cells x ml wort x degrees plato. Degrees plato = gravity of wort (whole number) divided by 4. There are 3785 ml in one gallon. So, lets say your original gravity is 1.060 and you have 5 gallons of wort. Degrees plato = 60/4 = 15. The recommended pitching rate would be 750,000 x 18,925 ml x 15 = ~213 Billion cells. An activator smack pack is supposed to contain 100 Billion cells. If you make a 1 liter starter without a stir plate you should end up with about 184 billion cells. Split into 2 would be 92 billion cells. Run the 92 billion cells through a another 1 liter starter and you should end up with about 164 billion cells which is enough yeast to pitch to a ~1.045 gravity beer.

If you use a stir plate for the 1 liter starter with a smack pack, you should end up with about 259 billion cells. Split into 2 would be 129 billion. Put that through another 1 liter starter and you end up with about 277 billion cells which is enough yeast to pitch to a ~ 1.077 gravity wort. So you see, there is no yes or no answer to your question but hopefully this will help you figure out what you need to do.

Question 3. You will most likely need a sanitized mason jar.
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09-07-2011, 07:23 PM   #3
huge1s
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Jul 2011
Monument, CO
Posts: 238
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Quote:
 Originally Posted by BBL_Brewer Well it depends. I use the Wyeast pitching rate calculator to figure out such things. http://www.wyeastlab.com/hb_pitchrate.cfm A lot of people use Mr. Malty. http://www.mrmalty.com/calc/calc.html Questions 1 & 2. Depends on whether you use a stir plate or not and what the original gravity of the wort will be. The recommended pitching rate for ales is .75 million cells x ml wort x degrees plato. Degrees plato = gravity of wort (whole number) divided by 4. There are 3785 ml in one gallon. So, lets say your original gravity is 1.060 and you have 5 gallons of wort. Degrees plato = 60/4 = 15. The recommended pitching rate would be 750,000 x 18,925 ml x 15 = ~213 Billion cells. An activator smack pack is supposed to contain 100 Billion cells. If you make a 1 liter starter without a stir plate you should end up with about 184 billion cells. Split into 2 would be 92 billion cells. Run the 92 billion cells through a another 1 liter starter and you should end up with about 164 billion cells which is enough yeast to pitch to a ~1.045 gravity beer. If you use a stir plate for the 1 liter starter with a smack pack, you should end up with about 259 billion cells. Split into 2 would be 129 billion. Put that through another 1 liter starter and you end up with about 277 billion cells which is enough yeast to pitch to a ~ 1.077 gravity wort. So you see, there is no yes or no answer to your question but hopefully this will help you figure out what you need to do. Question 3. You will most likely need a sanitized mason jar.
This helps a lot actually. I would assume I could make a larger starter (not using a stir plate) to get two batches of 100 million cells (original amount of smack pack). From there I could store one and use the other to make a new starter for pitching.

09-07-2011, 07:53 PM   #4
scottland
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May 2010
Chandler, AZ
Posts: 2,116
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1 & 2. Depends on your starter methods.

According to Mr. Malty a 1L starter will yield about 150 billion cells, which is only a 50% increase. If you used a stir plate, a 1L starter will yeild about 230 billion cells.

If no stir plate (simple starter) -- You'll want around a 1.8L starter to get 200 billion cells, which doubles what you started with.

02-05-2013, 06:31 PM   #5
PtreeCreekBrew
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Nov 2012
Posts: 68

According to Mr. Malty, if I take 1 smack pack, create a 1.16L starter at 1.055, I can generate ~200B cells, or double the pack.

If I then pitch half of that into a batch and package the other half, how long can I expect it to remain viable?

Do I simply re-calculate and do a new starter? And, if so, do I consider the production date (for viability purposes) as the date the yeast was originally manufactured, or the date that I did the original starter?

Thanks!

02-05-2013, 06:38 PM   #6
PtreeCreekBrew
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Nov 2012
Posts: 68

Also...I'm confused.

Mr. Malty shows that the maximum 5 gal batch that can be made with a single smack pack and no starter is 1.028.

That seems a little strange, then, that Wyeast would advertise that a pack is enough for up to 5 gals at 1.060. If this is underpitching (which...I can't say that I've ever had an issue with 1 pack in 5 gals of 1.050), why would they list it as adequate. Wouldn't they be more than happy to sell you more yeast?

02-05-2013, 07:24 PM   #7
BBL_Brewer

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Feb 2011
Kokomo, IN
Posts: 3,702
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Quote:
 Originally Posted by PtreeCreekBrew Also...I'm confused. Mr. Malty shows that the maximum 5 gal batch that can be made with a single smack pack and no starter is 1.028. That seems a little strange, then, that Wyeast would advertise that a pack is enough for up to 5 gals at 1.060. If this is underpitching (which...I can't say that I've ever had an issue with 1 pack in 5 gals of 1.050), why would they list it as adequate. Wouldn't they be more than happy to sell you more yeast?
They would love to sell you more yeast, but most people won't pitch \$16 wort of yeast for a 5 gallon batch. And 1 pack will work for a 1.060 brew, but it's not optimal. Why they advertise that is beyond me. It's been kicked around many times here on HBT. The rule of thumb for ales is .75 million cells per ml per degree plato.
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