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Old 05-05-2013, 05:58 PM   #1
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Default Pitching a yeast starter into already fermenting beer?

Hi all! Beginning brewer here.

I brewed this Imperial Red Ale last Wednesday:

http://www.midwestsupplies.com/fulton-s-libertine-imperial-red-ale.html

The OG was 1.070 and the recipe calls for 8% ABV.

Friday, I had seen no visible signs of fermentation (no bubbles in the airlock). The Wyeast that came with the kit sat in my fridge for 4 months before using it, AND I think I didn't give it enough time to come back to life... or something. So I assumed there was something wrong with the yeast.

So I went to the homebrew store, picked up some new yeast (a White Labs California Ale this time) and at the recommendation of the storekeeper, got a yeast starter kit, which he recommended for such a high gravity beer.

I wake up Saturday and, lo and behold, bubbles are happening in the airlock. So apparently the yeast just took a couple days to get movin' and shakin'.

My question: Should I still make a yeast starter for this batch? If I do, should I only pitch some of it? Is there danger in adding too much yeast to this recipe, especially because now they'd be two different types of yeast?

Thanks all for your input!

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Old 05-05-2013, 06:14 PM   #2
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Don't bother making a starter for this batch and adding it.

If you're seeing airlock activity now, you either have huge temperature swings (doubtful) or the yeast are already multiplying. Any off-flavors you are going to get from this big of an underpitch (yes, you will get off flavors) are already a done deal. You won't be able to create a big enough starter fast enough to combat it.

Sit back and RDWHAHB.

Edit: For reference, you pitched 25-50 billion cells. For 5 gallons of 1.070, your target pitch was 242 billion cells.

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Old 05-05-2013, 06:27 PM   #3
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What thadius said. Save your yeast for your next batch, this one's already underway. I've underpitched a couple times (not on purpose) and have not been overwhelmed with any off flavors/smells, so YMMV.

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Old 05-05-2013, 08:01 PM   #4
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ok, thanks for the advice. Will the ABV end up lower because of the underpitching?

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Old 05-05-2013, 09:01 PM   #5
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No, the underpitch just means they need to multiply extra generations before they get to work. You'll probably get the same ABV as long as they're not too strained. You'll just get the ester profile from all that multiplication. Usually we decant some of those esters off In the spent starter wort before pitching.

If youve never made this recipe before, arent very familiar with a clone, or have a well trained palette, you probably wont be able to tell the difference.

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Old 05-06-2013, 02:47 AM   #6
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Awesome, thanks for the info!

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Old 05-06-2013, 04:37 AM   #7
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Well... technically if you underpitch the yeast has to reproduce to reach that needed critical mass. They need resources to reproduce and the only resource around is your precious sugary wort.

So yes, they consume sugars to reproduce and there's going to be less of it for fermentation. You do the math...

To which extent, I don't know...

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Old 05-06-2013, 04:59 AM   #8
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Actually, if I wanted to guess, I'd calculate how much less abv you'll have by those simple steps:

-Use MrMalty to calculate how much DME you would have needed for a proper starter considering how old was your yeast. This is in theory how much fermentables your yeast would consume to reproduce in your wort.
-Let's say you are using Beersmith, add as much DME into your beer recipe. Your OG will go higher than your true OG was.
-Bring your OG back down to your real OG by removing just enough of your real fermentables (2row, other DME, whatever).
-Now that you're back to your original OG, check the estimated ABV which should be the same as before or very very close. Remove the DME you added relating to propagation. Note the new ABV.

I'm guessing that last ABV is going to be closer to the one you'll actually end up with. Now I just imagined that so I don't even know how it will end up. Might not even be a lot less, but it's still interesting... ;-)

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Old 05-06-2013, 11:48 PM   #9
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For fun, if anybody cares:

Made a 19 liters batch (5 gals) in BeerSmith.

6kg 2row up to 1.070 OG and 8% estimated ABV.

With yeastcalc.com, it says I need to do a 9.4 liters starter using 949g DME (33.4gal).

Added this amount of DME into BeerSmith (upped ABV to 10.1%).

To get it back down to 1.070/8%, I had to scale down the 2row from 6 kg to 4.45kg.

Assuming the yeast will grow to the same amount of yeast compared to a healthy starter and then start the fermentation, I remove all the DME from the recipe. That might not be right. It's a definite possibility that the yeast will grow to a lower mass before starting the fermentation.

So let's say I remove:

100% of the DME (yeast mass=yeast mass from a healthy starter):
1.052 of OG left for fermentation, ABV=5.8%

75% of the DME (yeast mass=75% of yeast mass from a healthy starter):
1.056 of OG left for fermentation, ABV=6.4%

50% of the DME (yeast mass=50% of yeast mass from a healthy starter):
1.061 of OG left for fermentation, ABV=6.9%

25% of the DME (yeast mass=25% of yeast mass from a healthy starter):
1.066 of OG left for fermentation, ABV=7.4%

I'd be surprised if the yeast was propagating as much as in a healthy starter, but I'm thinking 50% isn't unrealistic. In this case, you'd lose a big 1% ABV, which isn't negligeable at all...

Any thoughts?

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Old 05-07-2013, 02:48 AM   #10
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Okay, there's some math errors in here that are really throwing you off. Let's go line by line.

For starters (pun intended), you would want to cold crash for 24-36 hours to preserve the less flocculant, more attenuative yeast from being decanted off. Then, you pour off the liquid, leaving only the yeast to pitch to the beer. Thus, the DME or AG used in the starter does not add appreciably to ABV because almost all of the alcohol went down the sink drain.

Quote:
Originally Posted by atreid View Post
For fun, if anybody cares:

Made a 19 liters batch (5 gals) in BeerSmith.

6kg 2row up to 1.070 OG and 8% estimated ABV.

With yeastcalc.com, it says I need to do a 9.4 liters starter using 949g DME (33.4gal).
We already have some odd errors going on here. For 5 gallons of 1.070, you want to pitch 242 billion cells. This can be done on a stir plate using Brau Kaiser's (K. Troester's) growth model, which gives a starter of 1.1 liters (assuming 1.040 starter wort). That's about 110g of DME in 1.1 liters of water, for reference, using the off-the-cuff magical 10:1 ratio. YeastCalc gives a more precise 4.22 oz, which is 119g of DME.

Quote:
Originally Posted by atreid View Post
Added this amount of DME into BeerSmith (upped ABV to 10.1%).
As said above, you don't get any appreciable addition to ABV from a starter. The point is to grow yeast cells fast, not make beer, so the spent starter wort will negatively affect your beer if pitched.

Quote:
Originally Posted by atreid View Post
To get it back down to 1.070/8%, I had to scale down the 2row from 6 kg to 4.45kg.

Assuming the yeast will grow to the same amount of yeast compared to a healthy starter and then start the fermentation, I remove all the DME from the recipe. That might not be right. It's a definite possibility that the yeast will grow to a lower mass before starting the fermentation.

So let's say I remove:

100% of the DME (yeast mass=yeast mass from a healthy starter):
1.052 of OG left for fermentation, ABV=5.8%

75% of the DME (yeast mass=75% of yeast mass from a healthy starter):
1.056 of OG left for fermentation, ABV=6.4%

50% of the DME (yeast mass=50% of yeast mass from a healthy starter):
1.061 of OG left for fermentation, ABV=6.9%

25% of the DME (yeast mass=25% of yeast mass from a healthy starter):
1.066 of OG left for fermentation, ABV=7.4%

I'd be surprised if the yeast was propagating as much as in a healthy starter, but I'm thinking 50% isn't unrealistic. In this case, you'd lose a big 1% ABV, which isn't negligeable at all...

Any thoughts?
This whole section no longer applies.
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