Author Topic: Amount of water and IBU's  (Read 1648 times)

flbrewer

• Brewmaster General
• Posts: 2161
Amount of water and IBU's
« on: June 03, 2013, 12:56:34 PM »
I believe I read that IBU's can rise when you use more than x amount of water in an extract boil. How is this?

dzlater

• Brewmaster
• Posts: 518
• Dan S. New Jersey
Re: Amount of water and IBU's
« Reply #1 on: June 03, 2013, 01:05:24 PM »
The theory is that higher gravity wort will have a lower level of hop utilazation.
So the thinner the wort the more bitterness one would get from the same amount of hops.
« Last Edit: June 03, 2013, 01:08:05 PM by dzlater »
Dan S. from NJ

hubie

• Assistant Brewer
• Posts: 234
Re: Amount of water and IBU's
« Reply #2 on: June 04, 2013, 07:40:40 AM »
John Palmer has a nice table (Table 7) that shows hop utilization percentage as a function of boil time and wort gravity:  http://www.howtobrew.com/section1/chapter5-5.html

Pick a boil time, say 60 minutes.  You get about 28% utilization from your hops if boiling in a 1.030 solution whereas you only get about 18% if you were boiling in a 1.080 solution.  This isn't all that big a deal for people who do full-boils, but if you're doing partial boils using extract, this could become an effect you'd want to compensate for (in this example, you'd want to increase your 60-minute hops by about 50%).

a10t2

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Re: Amount of water and IBU's
« Reply #3 on: June 04, 2013, 07:59:48 AM »
The other thing to keep in mind is that the solubility limit for alpha acids is around 100 IBU. So if you're doing a 3 gal boil and diluting to 5.5 gal, for example, you can never exceed 100*3/5.5 = 55 IBU, give or take. If you've developed a recipe that takes advantage of that without realizing it, switching it to a less dilute concentrated boil could result in increased bitterness.
« Last Edit: June 04, 2013, 08:19:36 AM by a10t2 »
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morticaixavier

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• Underhill VT
Re: Amount of water and IBU's
« Reply #4 on: June 04, 2013, 08:01:25 AM »
The other thing to keep in mind is that the solubility limit for alpha acids is around 100 IBU. So if you're doing a 3 gal boil and diluting to 5.5 gal, for example, you can never exceed 100*3/5.5 = 55 IBU, give or take. If you've developed a recipe that takes advantage of that without realizing it, switching it to a lessmore-dilute boil could result in increased bitterness.

fixed that for you. but the concept is there. if you dilute less post boil you will get better hop utilization
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a10t2

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Re: Amount of water and IBU's
« Reply #5 on: June 04, 2013, 08:19:58 AM »
Yeah, that. I've had coffee now.
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saintpierre

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• Augusta, ME
Re: Amount of water and IBU's
« Reply #6 on: June 04, 2013, 08:35:57 AM »
This is one of the reasons extract brewers tend to add a majority of the extract with 5 or so minutes left in the boil to get a better hop utilization.
Mike St. Pierre, P.E.
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flbrewer

• Brewmaster General
• Posts: 2161
Amount of water and IBU's
« Reply #7 on: June 04, 2013, 09:53:08 AM »
This is one of the reasons extract brewers tend to add a majority of the extract with 5 or so minutes left in the boil to get a better hop utilization.
I've never done that, what am I missing?