HOMEBREW Digest #4951 Mon 13 February 2006

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  yeast oxygenation/stir plates (ALAN K MEEKER)
  Re: metallic taste in reconditioned keg (Dylan Tack)
  Big Beer Efficiency problem? Or no problem? ("Michael Eyre")
  wooden casks for homebrewing; use furniture legs (Raj B Apte)
  Re: Hop Isomerization ("Greg 'groggy' Lehey")
  Growing hops (Bill Velek)

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---------------------------------------------------------------------- Date: Sun, 12 Feb 2006 22:57:48 -0500 From: ALAN K MEEKER <ameeker at mail.jhmi.edu> Subject: yeast oxygenation/stir plates John Peed asked about the role of oxygenation and stir plate usage during yeast starter prep. Basicaly, oxygen is required for the synthesis of certain components of the cell membrane (not the cell wall which surrounds the cell membrane). During the actual fermentation, where oxygen is (hopefully!) excluded, the concentration of these compounds limits the number of cell divisions that can take place since the compounds are divided up between the mother cell and the daughter cells. Once the lower limit required for membrane function is reached, cell division ceases. In addition to limiting the expansion potential of the yeast population, depeltion of these membrane compounds can lead to less healthy and robust yeast which can negatively affect the fermentation, particularly if it is a stressful one (e.g. high gravity). How does a stir plate speed starter growth? The mixing action of magnetic stirrers promote starter growth in a couple of ways. For one, it helps aerate the starter wort, which allows the yeast to maintain healthy membranes and continue dividing during the starter growth. Of course this does depend on having air or oxygen input to starter. Continuous mixing also helps to remove CO2 generated by the yeast and keeps the yeast cells suspended and mixed well with the nutrients in the wort, all of which encourages healthy and rapid yeast growth. Is there risk of oxidation by pitching the whole starter? Well, there's no risk of oxidizing the main wort by addition of the starter as this is the stage in whgich you want to aerate the wort anyway. However, one would think that the starter wort itself should be highly oxidized and that you woudn't want to add this to your main wort at pitching. I thought this myself, but I've heard from enough people who do this (even had some of their beers) who say it does not hurt the finished beer, that I now believe it doesn't adversely affect the final quality. Why this is, is not exactly clear to me. It may be that the compounds generated during the starter growth are metabolized by the yeast during the several days of primary fermentation, or, if volatile enough, may be "scrubbed out" by all of the CO2 generated. Alan Meeker, Baltimore MD Return to table of contents
Date: Mon, 13 Feb 2006 10:07:32 -0600 From: Dylan Tack <dylan at io.com> Subject: Re: metallic taste in reconditioned keg > Date: Sun, 12 Feb 2006 19:37:08 -0500 (EST) > From: Aaron Martin Linder <lindera at umich.edu> > > I don't know what the residue was. Perhaps a layer of metal oxide > leached off of the keg after SABCO's processing. > I'm not sure exactly how Sabco reconditions them. But it's possible that there is some raw metal exposed. Normal stainless still has a thin, invisible layer of chromium oxide, which is what gives it its corrosion-resistant properties. You might try "passivation", which is basically washing it with weak nitric acid to encourage the formation of this layer. It will form spontaneously without your help, but there may be advantages to using the acid (such as removing iron compounds from the surface). -Dylan Return to table of contents
Date: Sun, 12 Feb 2006 11:45:43 -0800 From: "Michael Eyre" <meyre at sbcglobal.net> Subject: Big Beer Efficiency problem? Or no problem? Hey all. Brewed up a larger than normal beer (than our usual) this weekend. About 32 lbs total if memory serves. 25lbs of Pale 2row, a pound and a half of Roasted Barley and Dark crystal 120L and a bit less than the above of chocolate malt too. A couple lbs of Wheat and Flaked Barley rounded it out. A 10.5 gallon batch it turned out to be at 1.076, when we were shooting for 1.085. We're usually right on the nose accurate with our smaller brews (within' a point or three...) so we were wondering why this one fell so short of what we had hoped to get. Is there anything about bigger beers and an efficiency curve? We mash in a 1/2bbl keg with a slotted pipe manifold, FWIW. Like I said, we're usually right on the money, but really fell short this time. We did have a bit of a stuck mash, but we figured that out after about 1/2 hour to 45 minutes or so... really slow runoff after that. Batch sparge too, if that matters. Our efficiency numbers are usually 80-83%, and this time it was more like 71% efficient. Anything I mentioned here strike a chord with any one??? As a side note, this beer was pitched onto the yeast slurry from a Safale US-56 dry stout of 1.045O.G. that I was asking about last week. Fermentation went of like a bomb in the primary! Thanks for the suggestions to use it, for all that responded. We'll let you know how she tastes in a while. Mike Return to table of contents
Date: Mon, 13 Feb 2006 11:48:27 -0800 (PST) From: Raj B Apte <raj_apte at yahoo.com> Subject: wooden casks for homebrewing; use furniture legs All, Wooden barrels may serve to modify beer in several ways: 1. oak flavour. you can get this cheaply from chips. 2. flavour of whatever was in the barrel before. 3. micro-oxygenation of the beer 3a. micro-oxygenation of the beer with Brett or other critters. For 1 and 2, you are on your own. Use some chips or chips soaked in brandy &c. For 3 and 3a, I've gone through the numbers on my site (search apte flemish sour ale). Tank Volume [L] O2 cc/L.year Burgundy barrel 300 8.5 Rodenbach tank, wood, small 12,000 0.86 Rodenbach tank, wood, large 20,000 0.53 HDPE bucket 20 220 Homebrew barrel 40 23 Glass carboy, 30cm vinyl immersion tube 20 0.31 Glass carboy, silicone stopper 20 17 Glass carboy, wood stopper 20 0.10 As you can see, if trying to reproduce Rodenbach or lambic (burgundy barrel or larger), you want 1-10 cc O2/L.year. Small barrels will give a few times more than that, and plastic barrels will give WAY too much oxygen. The solution that I use to this problem is to bung by glass carboys with oak dowels. The dowels are auto-clavable, toastable, and--with a bit of teflon tape--may seal the cask well. Don't do this if there is any chance of pressurizing the carboy!!! The dowels I use are sold for $2 for furniture legs--cheap american oak. A few days soaking removes much of the oak taste (inappropriate in sour ales to style). According to the table, they allow too little oxygen, but bungs are end-grain, which may have 5-10x more diffusivity. Actually, I suspect its more than that. I also have a few 60L oak barrels from morebeer.com. They work pretty well. Don't blame me if your carboy explodes. I have 10 bunged carboys at my place and haven't had a problem yet (some are 2 summers old). best, raj Return to table of contents
Date: Tue, 14 Feb 2006 08:31:27 +1030 From: "Greg 'groggy' Lehey" <grog at lemis.com> Subject: Re: Hop Isomerization On Saturday, 11 February 2006 at 8:35:07 -0900, Martin Brungard wrote: > > John Peed recently posted an item regarding hop isomerization that > should be expanded upon. Thanks for the information. It has answered some questions I haven't got round to asking yet. > Whole hops do require a rolling boil in order to help expose and > burst the lupulin glands. But the degree of the exposure and the > degree to which the lupulin glands were burst during harvesting and > packing will always be in question. While this is doubtless true, isn't this taken into account by the means of measurement? And doesn't it apply equally to pelletized hops? > The degree of utilization of alpha acids is very much in question > when using whole hops. Agreed, but not for the reason you state above. So: when using whole hops, should they first be shredded? I've tried putting the hops into a blender, adding some wort out of the pot, and blending them. The results are relatively inconclusive, of course, but it seems a reasonable approach. Greg - -- Finger grog at lemis.com for PGP public key. See complete headers for address and phone numbers. Return to table of contents
Date: Mon, 13 Feb 2006 18:47:37 -0600 From: Bill Velek <billvelek at alltel.net> Subject: Growing hops In reply to my inquiry about supports for growing hops, Stencil wrote in HBD#4947: > I use 20-foot masts, made of 2-1/2 and 3-inch pvc pipe - just > slip-assembled, no cement - that are socketed on re-bar pins. snip What, exactly, do you mean by "socketed". Another poster, different forum, does something similar; he has a pipe set in the ground, uses a tall pipe of the same diameter, and a length of pipe (larger diameter) as sleeve to join the two pieces. When it's time to harvest, he lifts the mast out of the larger supporting sleeve, and lowers it to the ground. I presume two people would does this together, with one on each mast. > A pair of masts supports a 30-ft spanwire of braided para cord from > which the jute bine-support lines dangle. snipped other details of design. Thanks, Stencil. Good info that I can use if I go that way. I've also been reading posts from folks who say that it isn't absolutely necessary to have the hops grow straight up, and some of them use a trellis or arbor. One fellow who does that said that he gets plenty of horizontal growth and just stands and harvests the hops from overhead. That appeals to me, too, because several people have written that it is better to not wait until the end of the season to begin harvesting. So I'm still trying to work this out, weighing all of the pros and cons. Cheers, Bill Velek Join "HomeBrewers" international grid-computing team and help mankind by donating spare computer power for medical research such as cancer; we're in the top 9%, and we beat the MillerTime team: http://tinyurl.com/b7ofs Return to table of contents
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