HOMEBREW Digest #4635 Fri 22 October 2004

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  Fortnight Of Yeast, 2004 - location of invertase action? / Philosophy and communication ("Fredrik")
  My Head Hurts (Jim Bermingham)
  Sugar utilization - Practical Phil, Intransigent Dave (ALAN K MEEKER)
  Wyeast storage time (Calvin Perilloux)
  Insulating Keg Kettles ("Mike Eyre")

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---------------------------------------------------------------------- Date: Fri, 22 Oct 2004 08:25:25 +0200 From: "Fredrik" <carlsbergerensis at hotmail.com> Subject: Fortnight Of Yeast, 2004 - location of invertase action? / Philosophy and communication I combine this post with another question to Tobias and Forbes. (The fortnight question at the bottom.) - -------------------------------------------------- I feel a bit like a nucleation site and responsible for trigging the bursts of parallell/serial issues lately. I also confess beeing a yeast philospher :) The harder questions you ask, the more important does language, terminology and the proper construction of the question become. IMO, in real life more often than not, many questions are indeed fuzzy. While a computer would simply reject it as syntax error, a human philosopher will not do so, that is too easy. Once a question is properly posed and technically well defined answering it is often principally a matter of "computing" and thus from a philosophers point of view - trivial. I find the learning *process* itself intruguing. Sometimes I find the mechanism of concluding something more interesting that then conclusion itself. Facts are like matter, while the "why" is the essence of life. My experience is that many real problems, and almost *all* of the most profound ones, are fuzzy questions, and does require a "philosophical aspect" to solve them. You can not (currently) ask a computer something like, at what point of complexity does matter turn into life? It is a fuzzy question, yet I find it quite relevant and most humans does get the basic quest, but we lack logic to deal with it. This is were a computer fails, but a philosopher will invent new logic as needed. IMO one of the differences between a computing device and real intelligence is the capabiilty to invent new logic, and not turn into syntax error halts. What I am trying to say is that some of this discussions look to me a bit like we are computers here. I think everyone agree the basic (fuzzy) question, we want to know how yeast behaves. Look at something like this (*just in principle*, beware for tyupos) x = the entire set of variables, yeast, wort and fermentor (except time!) dglucose/dt = - fg(x)*glucose*yeast_active + + 0.5 * [ - fs1(x)*sucrose*invertase_wort - fs2(x)*sucrose*invertase_surfacebound ] dfructose/dt = - ff(x)*fructose*yeast_active + + 0.5 * [ - fs1(x)*sucrose*invertase_wort - fs2(x)*sucrose*invertase_surfacebound ] dsucrose/dt = - fs1(x)*sucrose*invertase_wort - fs2(x)*sucrose*invertase_surfacebound dmaltose/dt = - fm(x)*maltose*yeast_active dmaltotriose/dt = - fmt(x)*maltotriose*yeast_active note that the equations account for the active yeast. The dormant yeast does not consume wort sugars. So once the yeast go dormant, the remaining sugars will be left as residuals. f are different regulations. Let's assume some typical enzyme kinetics (michaelis-menten) this might be something like fg(x) = ag(x) / { glucose + kg(x) } ff(x) = af(x) / { fructose + kf(x) } ..etc where ag() and kg() are further regulations to find out, so using knowledge, I will keep expanding thse regualtors, until I reach a level where it's reasonable to think thet are constants, then these will be my model parameters, and of course each parameters should be intristic to yeast, wort or fermentor. Ther must not be parameters that depend on everything. The problem would be to find these regulations. The model will be *crowded* with these regulation functions, and they must all satisfy balancing of energy, redox, carbon, nitrogen etc. So training the model is to keep tweaking the regulation *functions* and also to tune in the parameters. On thing I failed to find is if the invertase enzymes are cellbound or expelled freely into wort, or both??? I know that in theory there are both options but for brewing yeast I don't know which is relevant? I think I asked this question before on here long time ago but I got no comments. Worst case I have to account for both, like above. Any ideas? - -------------> Fortnight question to Tobias and Forbes. (As speculated above) Where is the location of action of invertase splitting sucrose? I wonder if it is all expelled into the wort, or if there is also relevant activity on the cell surface suface bound inverase? I remember reading some cells do have cellbound sucrose enzymes, what is that the case for S.C? /Fredrik Return to table of contents
Date: Fri, 22 Oct 2004 08:14:12 -0500 From: Jim Bermingham <JBHAM6843 at netscape.net> Subject: My Head Hurts My head hurts. I think I have an "ose" headache. With all the glucose, fructose and sucrose being batted around on the HBD and finding out that I am in the 1% minority of the HBD readers because I'm not sophisticated enough to understand Brettanomyces/Dekkera sp., my head is splitting. Here I am, just back from two weeks of lavish living in Sin City, Nevada, already feeling bad because I lost the shirt off my back and thought I would have to sell the farm just to pay my gambling debt. And instead of relaxing and settling back to enjoy catching up on all the post I missed I get this feeling that all of a sudden no one is interested in brewing beer and sharing ideas on ways to improve their brewing. " I'm smarter than anyone else about most things, and I'm going to prove it" seems to be the attitude of the day. Maybe I'm missing the point and if I was much smarter than I am I would see where all this would improve my brewing enough to beat Bev Blackwood in at least one of the brewing competitions. But I still refuse to wear a skirt like Bev does. He has better looking legs than I do. I don't know if knowledge of the "ose" or his good looking legs is the key to all his ribbons. Enjoyed all the beers from The Chicago Brewing Company and the Triple 7 Brewery while in Vegas. If anyone happens to be in Millsap Texas come on by and we will have a few beers. Iif you can't come, send money I have some debts to pay. Can't brew with two broken knee caps. Jim Bermingham Millsap, TX Return to table of contents
Date: Fri, 22 Oct 2004 09:23:52 -0400 From: ALAN K MEEKER <ameeker at mail.jhmi.edu> Subject: Sugar utilization - Practical Phil, Intransigent Dave My associate Phil Yates asks, what /practical/ use is there in discussing the details of yeast sugar utilization? Well Phil you are correct, this topic isn't likely to have much (if any) practical benefit to the average homebrewer. Rather this falls into the class of more esoteric/technical discussions that often take place here. Since the que has been short lately these posts aren't displacing any other discussions, and there are certainly folks interested in such details regardless of their potential to directly help out one's brewing practice. Remember, the PgDn key is always nearby... :) Dave Burley commented: "As I have often in the past, I will forgive what I perceive to be an arrogant tone and ask that you focus on the issue which you brought up." -What you perceived as arrogant was merely exasperation on my part. If you re-read what I posted you'll see that it focuses /entirely/ and succinctly on the one topic I brought up - that of sequential sugar use. "I commented from the beginning of my discussion ( with /Fredrik) about glucose blocking certain pathways and many other comments relating to using a kinetic and not a misunderstood "energy" approach in /Fredrik's <fermentation modelling> work." -What you ALSO said /repeatedly/ (which I cited in my last e-mail) was that the concept of sequential sugar utilization was incorrect and that this may be part of Fredrik's problem in modelling. This is what I responded to and is the only topic I have been addressing. "But as far as the discussion topic which you chose to open, about what happens in the yeast cell, as far as I know, glucose does not block the parallel assimilation of fructose or sucrose. If you have any evidence besides your opinion, I'd like to see it" -I never said glucose blocks fructose or sucrose. What I have said, and what was confirmed by Fischborn and Waldrop, is that glucose blocks maltose and maltotriose uptake. Again, pretty simple idea. -Alan Meeker Return to table of contents
Date: Fri, 22 Oct 2004 07:53:34 -0700 (PDT) From: Calvin Perilloux <calvinperilloux at yahoo.com> Subject: Wyeast storage time [Robert Zukosky asks about the state of his nearly 4-year-old Wyeast smack pack that took 6 days to expand.] Not to worry (much). If the package expanded, you're probably in good shape. You'll have FAR fewer yeast cells than in a fresh pack, though, so careful attention to starter sanitation is recommended. You might also consider a multistage starter, beginning fairly small (250 ml or even 100 ml?) before working up, since you are beginning with so few viable cells. I've used smack packs that have been in the fridge for 4 years, and I've had normal fermentations with no problems or off-flavors; this is when using at least a two-stage starter culture to get the cell count up to something reasonable. Calvin Perilloux Middletown, Maryland, USA Return to table of contents
Date: Fri, 22 Oct 2004 10:55:53 -0400 From: "Mike Eyre" <meyre at sbcglobal.net> Subject: Insulating Keg Kettles Hey all.. looking for info on good ways to insulate a keg mash kettle. Did some searching on the matter and found surprisingly little info out there. Saw some designs with a rather elaborate outside skeleton of various materials, but that bulks up the keg a lot and they're heavy enough for me to lift off the second rack of my gravity feed design. Saw some others with some sort of jacket.. curious if this is the best approach for light weight and easy access to the tun when needed.. what are you all doing? Mike Return to table of contents
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