HOMEBREW Digest #4845 Mon 12 September 2005

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  photodecomposition of beer ("Peter A. Ensminger")
  Hops ("William Frazier")
  Source of Chlorophenols in my Beer? ("Eric R. Theiner")
  Using chest freezer with dorm fridge attached (Aaron Martin Linder)
  more esters, and also acids (Matt)

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---------------------------------------------------------------------- Date: Mon, 12 Sep 2005 00:00:49 -0400 From: "Peter A. Ensminger" <ensmingr at twcny.rr.com> Subject: photodecomposition of beer For all you beer geeks out there ... A recent review article entitled: 'Shining Light on the Photodecomposition of Beer' by Kevin Huvaere & Denis De Keukeleire (Ghent University, Belgium) has been published in "The Spectrum". The full text is here: www.bgsu.edu/departments/photochem/research/summer2005spectrum.pdf This new review article discusses recent research on the mechanism of the flavin-mediated light-struck reaction, which leads to formation of 'skunky' mercaptans following exposure of beer to blue light. Cheerio! Peter A. Ensminger Syracuse, NY http://hbd.org/ensmingr/ Return to table of contents
Date: Mon, 12 Sep 2005 00:27:37 -0500 From: "William Frazier" <billfrazier at worldnet.att.net> Subject: Hops I've spotted some wild hops growing near my house. When are hops ready to pick? What are signs of hop flower maturity? Thanks. Bill Frazier Olathe, Kansas USA Return to table of contents
Date: Mon, 12 Sep 2005 9:01:53 -0500 From: "Eric R. Theiner" <rickdude at tds.net> Subject: Source of Chlorophenols in my Beer? Hey brewpeople, I've got a chlorophenol problem that I'm trying to track down and I think I might have got it limited to one of two sources... and I think I know which one, but I'm going to put it to the group. The first possibility is the water-- I'm in Madison, WI using the local water after it goes through my ion-exchange softener (strips out Mg & Ca and replaces with Na, then goes the other way with a brine regeneration). The water here is pretty alkaline, so I pre-boiled with extra calcium added via calcium chloride to precipitate out a bit of the carbonate, and then blended in fresh water that had not been pre-boiled. I still had to use a good bit of acid blend to get my mash pH right, though. Anyway, I understand that the chlorine content in my water will hit a top end of 4-5 ppm, and this is through hypochlorite, not through chloramines. The second potential source would be my drinking water grade hose-- I think. I never had a "green hose" flavor from this hose before ('cos it's white, after all). But I ran some hot water through it here and there, and only later learned that you're not supposed to do that. Recently, I ran some water through it and caught it in a glass and that water was vile! Not infected or moldy or anything, but very "hosey." Being as all of my brewing water moves through this hose, could that be the initial source of my chlorophenols? Thoughts are appreciated! Rick Return to table of contents
Date: Mon, 12 Sep 2005 12:04:02 -0400 (EDT) From: Aaron Martin Linder <lindera at umich.edu> Subject: Using chest freezer with dorm fridge attached Hi all, I have a question about using an old chest freezer that I have. The freezer does not work, the compressor runs, but it must have a freon leak, as it runs for awhile then shuts the compressor off. Anyway, I have been told it is not worth fixing it. So, I was wondering if anyone has any practical experience with connecting a dorm fridge or other cooling device to a chest freezer to use as a fermentation chamber? I have an approximately 1.5-2 ft^3 dorm fridge. I was thinking about cutting two 4 inch holes in the side of the chest freezer and inserting one/two duct fans (had them lying around anyway) blowing in opposite directions into and out of the chest freezer cavity as well as the dorm fridge, which would be sealed against the side of the chest freezer. I would then connect the two duct fans and the refrigerator into a power strip that would connect into a temperature controller with its probe in the chest freezer. This way I can use the insulating capacity of the chest freezer without throwing it out and also use my dorm fridge. Do you have any advice on the design? Is the dorm fridge going to be able to handle the task? I want to be able to at least go down to 60 degrees F for some ales or maybe hit 32 F for a lager now and again with my ambient basement being around 70-75 in the summer. Would it be more efficient to just buy a used chest freezer or fridge and use that instead? I also thought about just putting a heating unit of some sort in the freezer and using it in my <= 20 degree F garage in the winter. Would this be more efficient? Thanks for any help you can offer. Aaron - -------------------------------------------- Aaron Linder Research Laboratory Specialist Associate The University of Michigan School of Public Health I 109 S. Observatory, Rm. 3610 Ann Arbor, MI 48109 734-764-4399 lindera at umich.edu - -------------------------------------------- Return to table of contents
Date: Mon, 12 Sep 2005 10:05:03 -0700 (PDT) From: Matt <baumssl27 at yahoo.com> Subject: more esters, and also acids Thanks to everyone who took the time to explain some things about ester formation (and hose problems). Among other things, Steve explains how "stuck ferments" (shortage of some growth factor other than sugar causes yeast to stop growing) are likely to lead to increased acetate esters in practice. Unless the production of Acetyl-CoA (primarily from sugar) is halted at the same time that growth is halted, idle hands can make the Devil's work with the large surplus of Acetyl-CoA. Perhaps more the Duvel's than the Devil's in some happy cases. In the interesting theory reported by John Palmer, an increase in total growth leads to the production of more AAT enzymes, thus to more esters produced "after the growth phase." It seems that this could even provide an amplifying effect, in that acetate esters would be increased more than proportionally to the total growth. BUT, wouldn't any post-growth-phase production of acetate esters have to utilize acetyl-CoA that was produced before the sugar ran out, and now is just hanging around in the yeast cells (or possibly the beer)? Some points and questions: 1. I think pitching rate affects total growth ONLY because of the small amount of energy required for (non-growth-related) background maintenance of the cells. Posts (I recall some by Steve) in the archives suggest that this is a pretty small amount of energy and hence total growth should not change dramatically with pitching rate. But if there is a pool of Acetyl CoA laying around after growth stops, and AAT enzymes were produced in proportion to growth, then depending on reaction and denaturing rates, etc, small amounts if increased growth could lead to disproportionately large increases of acetate esters. 2. IS there a pool of Acetyl CoA lying around after growth stops? 3. Do fatty acids ever leave the cell walls and if so what is their fate? 4. More practically--can I increase the iso-amyl acetate in my beer, without increasing (and in fact reducing) isoamyl alcohol levels, by simply adding acetic acid to the wort? I assume not, because how would it get into the yeast cells and how would it get transformed to Acetyl-CoA... but who knows? Matt Return to table of contents
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