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Old 12-27-2011, 05:05 AM   #1
Brak23
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Default Two Questions - IBU & Half-Boil

So in using a new Beer program on the iPad I came across two questions that I would like to know.

1) I am going to be making an extract brew from Northern Brewer. It is an Imperial Stout (7.99%). It uses Summit Hops for the full 60 minute boil and gets an estimated IBU of 81.93. Is that high for a stout? I always was under the assumption that ~50 is the upper end for a stout. But does the fact that its imperial make having an 80+IBU ok?

2) In playing with some numbers in the beer program I saw that when I did a 5 gal full boil (accounting for boil off), that I got an IBU of 81.93. But when I adjusted the boil to 3 Gal (assuming that I will top of 2 gal at the end to make it 5gal total), I get an IBU of around 43. Why the large difference? Is this accurate? or is this just confusion on the brew software? I only have the ability to do partial boils with my 5gal stock pot right now, so I'm wondering why the numbers are showing the way they are right now.

Thanks guys and gals!


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Old 12-27-2011, 05:25 AM   #2
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1) Imperial stout should be 50-90+ IBU per style guidelines
2) the software is correct, partial boils mean higher gravity wort which will greatly affect hop utilization

cheers!


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Old 12-27-2011, 05:28 AM   #3
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one other thing, if the software allows play around with adding a portion of the extract late like 15 min to go. Among other reasons to do this (search) it will increase your hop utilization.
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Old 12-27-2011, 05:40 AM   #4
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Quote:
Originally Posted by chickypad View Post
one other thing, if the software allows play around with adding a portion of the extract late like 15 min to go. Among other reasons to do this (search) it will increase your hop utilization.
Current it 6 LBS of Dark Malt Syrup for 60 minutes and 6 LBS of Dark Malt Syrup for the last 15 minutes. However, when I played around with it (such as adding 1 Lb for the first 60 and the rest at the end) I'm still getting the same hop utilization. Ill do some searching though, because I've heard late extract helps.
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Old 12-27-2011, 05:46 AM   #5
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^^^^ ehhhh... Some of that stuff about high gravity wort causing less utilization is beginning to get debunked by even a few of those who at once might have touted it.... The reason partial boils provide less ibus is due to the dilution of the wort when topping up. If in theory as a homebrewer, you could get 100 ibus into a 2.5 gallon batch of wort, and then diluted to 5 gallons, it would stand to reason that the finished beer could only be 50 ibus.... Ibus on the homebrew level ain't perfect, but NB has it right with trying to get 50 ibu or so In that beer by dilution. Also, I'm not in the camp that late extract additions do much of anything for utilization.. It may be a percieved difference..They do however offer less carmelization and a truer color of the finished beer.
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Old 12-27-2011, 06:05 AM   #6
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hmm, maybe it's not as much of an effect with all extract. when I plug my partial mash batches into Beersmith and add all the extract at flameout vs 60 min it seems to calculate about 15-18% higher IBU.
I would check out the arguments for late extract though, I do think it helped my lighter beers.
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Old 12-27-2011, 06:06 AM   #7
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Quote:
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^^^^ ehhhh... Some of that stuff about high gravity wort causing less utilization is beginning to get debunked by even a few of those who at once might have touted it.... .
well there you go. didn't know it was one of the myths!
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Old 12-27-2011, 05:03 PM   #8
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^^^ I'm not saying its a myth just yet, it's that lately, guys like Palmer have been saying that more and more lately wort gravity appears to be unrelated to AA utilization. I agree with it because I can't taste a difference. Where I taste a difference is when doing a late extract addition and the wort doesn't suffer from carmelization.
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Old 12-27-2011, 05:07 PM   #9
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What program is it?
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Old 12-27-2011, 05:15 PM   #10
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Quote:
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What program is it?
iBrewMaster on iPad.


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