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	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
		Digest Janitor: pbabcock at hbd.org


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Contents:
  IIPA IBUs (Kevin Eggemeyer)
  Iso-alpha acid solubility (fljohnson52)
  Re: IIPA IBUs (Joe Walts)
  Re:  IIPA IBUs ("jeff_ri")


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Date: Mon, 27 Sep 2010 22:58:33 -0500
From: Kevin Eggemeyer <keggbrewer at gmail.com>
Subject: IIPA IBUs

In addition to the limit of how many IBU's you can get into a beer, there is
also a limit to the sensory perception of bitterness.  I have heard this
limit stated as 65 IBUs, but have not tested this myself and had always
believed the limit to be higher.  Of course, this is only the perception
limit for bitterness, not hop flavor/aroma.

Kevin
St. Charles, MO



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Date: Tue, 28 Sep 2010 7:11:27 -0400
From: <fljohnson52 at nc.rr.com>
Subject: Iso-alpha acid solubility

The maximum solubility of iso-alpha acids is not dependent on 
the maximum percent utilization of iso-alpha acids. If the maximum 
solubility is 90%, which I am not questioning, then one should 
be able to achieve this regardless of the efficiency of utilization. 
And it doesn't matter how one performs the additions. It is dependent 
on the properties of the solvent, temperature, and perhaps the 
concentration of other solutes. This list of factors is not
exhaustive, but it doesn't include percent utilization.
 
- --
Fred L Johnson
Apex, North Carolina, USA


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Date: Tue, 28 Sep 2010 15:30:38 -0500
From: Joe Walts <jwalts at gmail.com>
Subject: Re: IIPA IBUs

For what it's worth, I built a saturation limit into my recipe
spreadsheet.  I don't have access to my formulas right now (I'm still
in on a hospital computer, so I can't download anything), but you can
view them here if you know how to trace formulas in Excel:

https://sites.google.com/site/republicbrewpub/

The name of the file is Recipe_Gallons.xls.  I believe my formulas
follow the Tinseth model below 65 IBUs (modified to allow positive
bitterness contributions of late kettle and whirlpool hops), and then
linearly decrease the effectiveness of alpha acid additions so the
projection passes near one of the Deschutes data points (80ish actual
IBUs for a calculated 240ish IBUs?).  I don't remember if I included a
max IBU limiter, but the amount of hops needed to get to the Deschutes
example would be absurd.  I also did something with the Sierra Nevada
hop school results that were printed in Zymurgy or BYO a short while
back, but it may have just been a spot check of my calculations.
Considering the massive dependence of hop utilization on brewing
equipment and procedures, as well as the fact that perceived
bitterness is only loosely correlated with IBUs (and has its own
saturation limits), I'm comfortable with ballpark accuracy until it
can be improved upon by better experimental data.

Joe
Madison, WI


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Date: Tue, 28 Sep 2010 20:10:47 -0400
From: "jeff_ri" <jeff_ri at cox.net>
Subject: Re:  IIPA IBUs

Hi All,

  Interesting discussion in the last few HBDs about IBUs and solubility 
limits of alpha and iso-alpha acids.

  I've heard many times that the limit is "about 100 IBUs".  I'm not sure of 
the source for this and definitely don't have references to back it up.

  However, I made an American barleywine many years ago that had a predicted 
207 IBUs (Tinseth formula).  It measured at 115 IBUs using the ASBC method 
and a 1:1 dilution with distilled water.  The measurement was made about 13 
months after pitching the yeast.

  FWIW, YMMV.

Jeff McNally
Tiverton, RI
(652.2 miles, 90.0 deg) A.R.
www.southshorebrewclub.org



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