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Old 11-11-2011, 02:30 PM   #1
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Default Stuck fermentation or too efficient a mash

My recent all grain batch of AHS Fat Tire Ale clone appears to be stuck at about 1.019/1.020 (after three weeks, gr hasn't moved in two weeks). Expected fg is 1.011. Apparrent attenuation is 61% (instead of 75%). I'm usually ok with my fg being close, but this seems a bit farther than I'm comfortable with. I've started searching and reading up on how to get a stuck fermentation going again, but then I had a thought. I checked my numbers, and it appears that my expected OG was 1.047, mine was 1.050. I also noticed that expected efficiency of 75%, but my efficiency apparently was 88.5%. So now I'm wondering if I just converted to much starch and the yeast just can't handle the excess. Do I need to try to get the fermentation going again, or should I just resign myself to a slightly sweeter version of the beer. FWIW, samples taste great.

Some other info:
-I used Notty
-My readings have been adjusted for temp
-Beer is presently sitting at about 66 deg F

Thanks all

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Old 11-11-2011, 02:37 PM   #2
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What was your mash temp? This has a big effect. Its possible, maybe even likely in my opinion, that the yeast are done.

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Old 11-11-2011, 02:41 PM   #3
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I agree. It has most likely reached terminal gravity. If you want it more dry, mash at a lower temp next time like 148-150.

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Old 11-11-2011, 02:42 PM   #4
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Quote:
Originally Posted by gstrawn
What was your mash temp? This has a big effect. Its possible, maybe even likely in my opinion, that the yeast are done.
152. Stayed at that temp for the full 60 minutes.

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Old 11-11-2011, 02:56 PM   #5
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It's probably done, but you could try a warmer spot (like 70 degrees) to see if you can knock off a few more points.

Or you could just bottle it and it'll be great.

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Old 11-11-2011, 03:17 PM   #6
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Quote:
Originally Posted by TyTanium
It's probably done, but you could try a warmer spot (like 70 degrees) to see if you can knock off a few more points.

Or you could just bottle it and it'll be great.
Ok, I moved it to a warmer spot. Naturally, the move shook loose a little of the yeast cake, so maybe I'll get a little action. If nothing is different Sunday, I'll rack to the keg. If I notice a change I'll let it sit tight.

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Old 11-11-2011, 03:41 PM   #7
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Good plan. Some even suggest giving it a GENTLE swirl to resuspend some yeast, but your moving it is probably sufficient enough. If it drops a few points, great. If not, you still will have delicious beer.

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Old 11-11-2011, 06:43 PM   #8
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Quote:
Originally Posted by mhochman View Post
I checked my numbers, and it appears that my expected OG was 1.047, mine was 1.050. I also noticed that expected efficiency of 75%, but my efficiency apparently was 88.5%. So now I'm wondering if I just converted to much starch and the yeast just can't handle the excess.
where'd you get 88.5%? 50 vs 47 is only 79% efficiency

not sure what you mean by converted too much of the starch, it should always be all converted. and no, theres no yeast that couldn't handle that small of an excess anyway, esp notty. you may want to check your themometer, cuz notty shoulda tore thru that if you really mashed at 152F. hopefully the agitation and warmer temps get you the rest of the way tho
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Old 11-11-2011, 07:28 PM   #9
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where'd you get 88.5%? 50 vs 47 is only 79% efficiency

not sure what you mean by converted too much of the starch, it should always be all converted. and no, theres no yeast that couldn't handle that small of an excess anyway, esp notty. you may want to check your themometer, cuz notty shoulda tore thru that if you really mashed at 152F. hopefully the agitation and warmer temps get you the rest of the way tho
That's the number my software gave me, based on total grains and my pre-boil gravity reading. By converting too much I meant that isn't there always some starch that doesn't end up getting converted? That's why we don't all get 100% brewhouse efficiency, right? Or am I confused? I was thinking I converted more than typically gets converted for this amount of grain following the instructions I had.
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Old 11-11-2011, 07:35 PM   #10
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Quote:
Originally Posted by mhochman View Post
That's the number my software gave me, based on total grains and my pre-boil gravity reading. By converting too much I meant that isn't there always some starch that doesn't end up getting converted? That's why we don't all get 100% brewhouse efficiency, right? Or am I confused? I was thinking I converted more than typically gets converted for this amount of grain following the instructions I had.
All the efficiency is measuring is how much of the potential sugar you have released from the barley. The missing percentage is what you havent rinsed out of the mash. We don't get 100% because it is difficult to extract that last little bit without using mechanical means.
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