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


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Contents:
  RE: Sun-dried hops? ("David Houseman")
  Re: IIPA IBUs (mossview5)
  Re:  IIPA IBUs ("Spencer W. Thomas")


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Date: Mon, 27 Sep 2010 06:58:02 -0400
From: "David Houseman" <david.houseman at verizon.net>
Subject: RE: Sun-dried hops?

Doug,

I've never dried my hops in the sun, just laid them out on old window 
screens on saw-horses (good air circulation) in the shade.   I've used these 
with great success for flavor/aroma additions.  Not for bittering since I 
don't know the alpha acid content to be able accurately calculated IBUs.  I 
did however make entire batches with fresh picked hops (Harvest Ales) and 
that worked great.   The other use for the hops was for my lambics.  Just 
left all the hops in an open grocery bag in my basement for a year or more. 
Yes, they really did smell cheesey.   That worked well also.  Good lambic 
with those hops.

David Houseman



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Date: Mon, 27 Sep 2010 14:03:00 -0400
From: mossview5 <mossview5 at gmail.com>
Subject: Re: IIPA IBUs

Many brewers use the various hop utilization formulas to estimate their
bittering level in their beer.  Many of those formulas provide acceptable
estimates of bittering (iso-alpha content in mg/L).  Unfortunately, those
formulas don't adequately address the solubility limit of alpha acids and
iso-acids in wort and water.

As has been alluded to in previous posts on this subject, there is an
alpha acid solubility limit.  AJ's post and the Deschutes Brewery blog both
provide the implication.  I can add that there are several other
peer-reviewed journal articles that specifically point out that both alpha
acids and iso-alpha acids have limits in solution.

Probably the most definitive work to date on this subject is from Malowicki
and Shellhammer.  They were conclusive in establishing that the maximum
solubility of alpha acids is about 90 mg/L.  They also established that the
maximum conversion of alpha to iso-alpha is about 75 to 85 percent of the
alpha acid content.  That points to a maximum iso-alpha content of about
80 mg/L which is equivalent to 80 IBU.  So, no matter how much hop
volume and alpha acid content you throw in a wort, the maximum IBUs will
be about 80.

Fortunately, there are other bittering components from hops and other
wort components that add to the perception of bittering.  Unfortunately,
there is little research into this area since most beers are crafted far from
the alpha acid solubilty limit.  Components like beta acids, phenols, and
tannins add to the bittering perception.  So there can be a more bitterness
perception, it just won't be from iso-alpha acid content.

So next time someone says that they bittered to some astronomic level,
you can just snicker.  If they were aiming for a super bitter beer, the way
to really get there is to reduce the gravity of the brew to enhance the
BU:GU contrast.  By definition, an IIPA is going to be less bitter than a
similarly bittered IPA or PA.

Martin Brungard
Carmel, IN


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Date: Mon, 27 Sep 2010 14:42:41 -0400
From: "Spencer W. Thomas" <hbd at spencerwthomas.com>
Subject: Re:  IIPA IBUs

[Invoking janitorial privilege to reply early...]

Martin writes that because there is a solubility limit for alpha-acids 
of 90mg/liter, and because only 75 to 85 percent of the alpha-acids are 
converted to iso-alpha acids, that IBUs are capped at about 80.

That would be true if there was a strict sequence, without overlap of
1. Dissolve alpha-acids in the wort.
2. Convert dissolved alpha-acids to iso-alpha-acids.

But that's not what happens in the brew kettle. Instead solution of 
alpha-acids overlaps with conversion of dissoved alpha-acids to 
iso-alpha-acids. Thus, the iso-alpha-acid concentration can exceed the 
limit imposed by alpha-acid solubility.

Consider this thought experiment: add enough hops to dissolve 80mg/ml of 
alpha-acids, and boil to convert 75% of these to iso-alpha-acids. There 
will now be 60mg/ml of iso-alpha-acids and 20mg/ml of alpha-acids. Now 
add more hops to bring the dissolved alpha-acid content back up to 
80mg/ml. Boil again. More iso-alpha-acids will be produced (possibly as 
much as another 60mg/ml).

There are undoubtedly other limiters in play, though. There is a 
solubility limit on iso-alpha-acids, which I had thought was about 
100mg/ml. Conversion of alpha-acids to iso-alpha-acids may be inhibited 
by the presence of iso-alpha-acids. Also, the solubility of alpha-acids 
may be depressed by the presence of iso-alpha-acids.

But I am pretty sure that the limit is not 80. I know that Stone Brewing 
claims to have measured Stone 13 to be very close to 100 IBUs (they list 
it at "90+" on the bottle). Best citation I can find online for this is 
at Stan Hieronymus's blog, Appellation Beer,
http://appellationbeer.com/blog/how-many-ibu-about-one-hundred/

There's also an interesting comment there from Stone brewmaster Mitch 
Steele about the solubility and thus the IBU level decreasing as the 
beer becomes more acidic during fermentation.

=Spencer in Ann Arbor


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