HOMEBREW Digest #5743 Mon 27 September 2010

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  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 Return to table of contents
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 Return to table of contents
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 Return to table of contents
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