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Old 06-05-2012, 02:28 PM   #1
Robusto
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Hi all. As I am moving from brewing other people’s tried and true recipes to experimenting with my own recipes, I find myself wondering if you can over pitch yeast. I know that you can under-pitch, and that can cause problems- particularly with lagers, but what about adding too much yeast? I ask because I have been making my test batches in 2 gal batches, that way if they are bad I only have 12-16 beers instead of 40 (16oz bottles) So, within reason, can you pitch too much yeast? If you do, what are the negative effects on the beer?

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Old 06-05-2012, 02:33 PM   #2
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Yes, you can.

It's probably not easy to do on a homebrew scale, but it's possible! Maybe pitching a small-ish beer on a yeast cake would get you to overpitching levels.

If overpitched, the yeast would not go through their "growth cycle" that they normally do if pitched in the proper amount. This results in few new yeast cells, and this can result in underattenuation as well as have a flavor impact.

I think it's more likely to underpitch than overpitch, but brewers should be aware of the possibility.


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Old 06-05-2012, 02:38 PM   #3
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Quote:
Originally Posted by Yooper View Post
I think it's more likely to underpitch than overpitch, but brewers should be aware of the possibility.
This.

If you are using an entire yeast cake for another beer of the same volume and same gravity, that is over pitching, and you will likely see less yeast character in the beer.

Using about one third to one fifth of a yeast cake again for the same beer (same volume and gravity) is about right. You can more or less scale up from their linearly. (That is, if you are brewing twice as much, use twice as much yeast, etc.)

 
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Old 06-05-2012, 02:39 PM   #4
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You can get off flavors from over pitching. Most homebrewers under pitch. Since you are making 2 gallons it is a little easier to over pitch than a 5 gallon batch but I would bet you won't over pitch. Use Mr malty to figure out how much to use based on OG and the type of yeast you use.
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Old 06-06-2012, 02:33 AM   #5
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I'm making a 2.5 gallon match of my Oatmeal Stout. When I did 5.5 gallons I used a starter for wlp002. Can I just pitch the whole vial for a half batch in lieu of a starter or is that over-pitching?

 
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Old 06-06-2012, 11:02 AM   #6
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Run a starter to make sure the yeast are happy. Just not a big one. I had a smack pack that took a week and half to swell up. Then it was good to go

 
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Old 06-06-2012, 02:25 PM   #7
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I'm not sure I even have enough dme for a starter, but should be enough to wake the yeasties up

 
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Old 06-06-2012, 03:00 PM   #8
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Quote:
Originally Posted by johnbrain View Post
I'm not sure I even have enough dme for a starter, but should be enough to wake the yeasties up
I'm going to dissent here. The only reason to make a starter for a batch that small is to check and see if the yeast are viable. If the vial is fresh (they have dates on them), then it WILL be viable and there is no need to make a starter for a 2.5G batch.

Yes, you can pitch the whole vial. No. It is not overpitching. I do no have your recipe and can run it through mr. malty, but sometimes we overthink this stuff. Making a weak starter without enough dme is not a good alternative to just pitching the vial after giving it a couple hours to rise to pitching temp. Just make sure IT rises to pitch temp and your wort COOLs to pitch temp and you'll be just fine.
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Old 06-06-2012, 04:00 PM   #9
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Mr Malty doesn't suggest starters <1L. Following this with a stirred starter may create almost double the yeast necessary for a 2.5 gallon batch. This site (http://yeastcalc.com/) gives a little more information and allows the user to input the volume.

I do 3.5 gallon (end-of-boil) batches and have never made a stirred starter <1L. I either just accept overpitching 25%-50% (and haven't regretted that yet) or decanted & shaken up the starter really well and poured in the portion I need based on http://yeastcalc.com/. If you pre-weight your container and stirplate you can use weight to very accurately pitch a portion of a well stirred-up starter.

Sometimes a 0.5L-0.75L stirred starter would produce the required growth for a small batch. Does anyone have insight about if that small of a starter (innoculation rate>100 million/ml) is a better option (yeast health) than just using a porition of a 1L starter?

 
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Old 06-06-2012, 07:31 PM   #10
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Meh. I respect Yooper's opinion but I'm in the camp that unless you are doing a specialty style that depends upon slight-underpitching for esters, etc, it's basically impossible to overpitch.

I've never seen it yet, and I'll throw tons of yeast into a batch. As long as it's HEALTHY yeast I would RDWHAHB.



 
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