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Old 10-04-2012, 07:40 PM   #1
billy66
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Default Not enough O2?

I just bottled a batch today from my secondary, and my gravity was a little high compared to where I expected. I had an OG of 1.052 and was expecting a FG of around 1.012. I got a FG of 1.020

I forgot to stir up the wort really good prior to pitching the yeast. I had the beer in the primary for 8 days (2 days longer than I normally do), so I figured no use checking gravity then (which I wish I did now). I had the beer in the secondary for 18 days.

Is it possible the lack of O2 in the wort caused the beer to not ferment all the way?

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Old 10-05-2012, 04:24 PM   #2
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Possible, but not very likely. There are lots of folks who don't aerate very well that get good attenuation. Most likely something else going on.

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Old 10-05-2012, 05:47 PM   #3
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Insufficient oxygen is but one cause of an incomplete fermentation - so maybe.

Others:
-Not enough yeast cells. Assuming you did 5 gallons, mrmalty shows you need 1.7B yeast cells, more than you get out of a normal smack pack - sounds like you didn't do a starter. That said, I've certainly had ~1.052 beers finish without a starter.
-Temperature got away from ideal range.
-If you did all-grain, high mash temps lead to more unfermentable sugars which leads to lower attenuation.

sorry man, hate it when beers don't finish up. Hope it still tastes ok @4.2%

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Old 10-05-2012, 09:45 PM   #4
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I think that the problem has more to do with only keeping it in primary for 8 days. Why did you transfer to secondary?

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Old 10-06-2012, 05:52 PM   #5
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Thanks for all the feedback.

- I transferred to secondary like I always do. Usually in less time, so I'd thought I'd be safe. (Next time I'll check my gravity).

- I did not do a starter, nor have I ever. Is this a big help in this area?

- Temperature was controlled by my basement, which stays at 65F this time of year. I even checked it a few times.

- I'll have to watch my mash temps better. This might be part of the issue. Thanks for the tip.

Thanks again.

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Old 10-07-2012, 06:48 PM   #6
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After I started using pure O2 my attenuation when up. I haven't had the 1.020 curse since....

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Old 10-07-2012, 07:00 PM   #7
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Just pitching a vial and not aerating, is very likely your problem. A low yeast count to begin with, and conditions not favorable for reproduction.

If you can keep it in the fermenter, you can make another beer and then move this onto the cake of that one when it is done.

Quote:
Originally Posted by danielbt View Post
I think that the problem has more to do with only keeping it in primary for 8 days. Why did you transfer to secondary?
Unless the temperature went low enough to drop the yeast, this will not be a problem. The yeast that is doing the work is still in suspension. I believe the yeast in the cake are still good to reduce diecetyl, and clean up some off flavors, but it is not making any alcohol.

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Originally Posted by michael.berta View Post
After I started using pure O2 my attenuation when up. I haven't had the 1.020 curse since....
I've never used O2, and have never had the 1.020 curse.
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Old 10-08-2012, 12:52 PM   #8
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Thanks for all the advice and input. I've already bottle this, so I'll just roll with it. We tasted it prior and it didn't taste bad... it was a test batch anyway (used some wild hops we found).

One other quick question. We brewed this batch to try and see how the hops perform. If the beer didn't ferment all the way, am I right to think that it will have more sugar, so more sweet... therefore less bitter flavoring from hops will show through?

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Old 10-08-2012, 07:02 PM   #9
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A couple of thoughts regarding this-

Which yeast was it?
What was the grain bill? Mash temp?

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Old 10-09-2012, 05:09 PM   #10
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Yeast vitality is just as important as cell count. A starter will help the yeast gain needed glycogen and trehalose (in addition to viable cell count) which will help compensate, to some degree, for lower O2 levels of the wort.

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