Author Topic: Under-attenuated Imperial Stout  (Read 5720 times)

therobot

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Under-attenuated Imperial Stout
« on: November 07, 2010, 03:07:55 PM »
Usually have 60% efficiency.  Calculated for a 1.097 OG.  Efficiency jumped up to 80%.  First time I did water chemistry changes.  Guess it helped. :P  Got the ferment temperature controlled, and it's stuck at 1.042, holding at 71 degrees.  Dropped from 1.044 to 1.042 in a week and a half, so it's still moving, but real slow.  Was thinking about getting my stir plate going, and pitching a bunch more US-05 to try and punch it through and down to 1.034ish.  It's still just a little too sweet, and I plan on bottling so I'm afraid of bottle bombs.  At the moment, the apparent attenuation is only 63%.  Here's the recipe:

Quote
Domer's Imperial Stout
Imperial Stout

Type: All Grain
Date: 12/28/2009
Batch Size: 5.00 gal
Brewer: 103rd St Brewery
Boil Size: 7.18 gal Asst Brewer: 
Boil Time: 90 min  Equipment: My Equipment - 5 Gal Batches 
Taste Rating(out of 50): 35.0  Brewhouse Efficiency: 80.00
Taste Notes: 
 
Ingredients
 
Amount Item Type % or IBU
3.00 lb DME Golden Light (Briess) (4.0 SRM) Dry Extract 15.00 %
10.00 lb Pale Malt (2 Row) US (2.0 SRM) Grain 50.00 %
2.50 lb Caramel Malt - 80L 6-Row (Briess) (80.0 SRM) Grain 12.50 %
1.50 lb Black Malt - 2-Row (Briess) (500.0 SRM) Grain 7.50 %
1.50 lb Chocolate (Briess) (350.0 SRM) Grain 7.50 %
1.50 lb Roasted Barley (300.0 SRM) Grain 7.50 %
1.50 oz Chinook [12.80 %] (60 min) Hops 42.0 IBU
1.00 oz Williamette [5.50 %] (15 min) Hops 6.0 IBU
 
Mash Profile
 
Mash Name: Single Infusion, Medium Body Total Grain Weight: 17.00 lb
Sparge Water: 4.71 gal Grain Temperature: 55.0 F
Sparge Temperature: 168.0 F TunTemperature: 55.0 F
Adjust Temp for Equipment: TRUE Mash PH: 5.4 PH
 
Single Infusion, Medium Body Step Time Name Description Step Temp
60 min Mash In Add 21.25 qt of water at 170.2 F 152.0 F
10 min Mash Out Decoct 7.34 qt of mash and boil it 168.0 F

Suggestions?

Offline JABrews

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Re: Under-attenuated Imperial Stout
« Reply #1 on: November 08, 2010, 08:41:18 AM »
I have found with some of my stuck ferments, just racking into another carboy sometimes jostles it enough to kick start it again.
Maybe try stirring it but then I would be worried about Oxidation or contamination issues if too much air gets in it etc.

Offline BobBrews

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Re: Under-attenuated Imperial Stout
« Reply #2 on: November 09, 2010, 05:35:12 AM »
How well did you oxygenate the wort when you started? I use pure oxygen when I start my primary fermentation. I try to give it a good minute or so while stirring with my wand. If your wort in not properly oxygenated it will only ferment until the oxygen runs out and then it chokes. Maybe you could take off the airlock and shake the poop out of it to get it going?
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therobot

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Re: Under-attenuated Imperial Stout
« Reply #3 on: November 11, 2010, 11:10:38 AM »
I used pure oxygen as well.  Really just afraid of incorperating any more oxygen because I don't want to risk oxidization.  If push comes to shove, I might actually try the olive oil trick to see if I could get a bit more 'oomph' into the wort.

Offline MaltLicker

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Re: Under-attenuated Imperial Stout
« Reply #4 on: November 12, 2010, 05:47:51 PM »
The only thing I've read that works at this stage is create a new starter and pitch it when it is at high kraeusen and actively feeding.  The hope is it survives the alcohol level and keeps eating the wort. 

therobot

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Re: Under-attenuated Imperial Stout
« Reply #5 on: November 21, 2010, 12:12:51 AM »
I know it's a newer thing as well, but I was thinking of maybe trying the olive oil trick with the new starter I was gonna make, in an attempt to make up for the fact that there's likely next to no oxygen left in the brew, and I can't oxygenate at this stage.  Any thoughts?  Since I started this, it's dropped another .002, so it's moving, just /slow./

Offline MaltLicker

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Re: Under-attenuated Imperial Stout
« Reply #6 on: November 22, 2010, 07:43:57 PM »
Worth a shot.  Adding the active yeast and transferring it carefully may revive the fermentation. 

 

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