HOMEBREW Digest #2812 Mon 31 August 1998

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  Alkalinity/Modes and Nodes/Tannin in Cyser/Stirring (AJ)
  yeast models/amino acids/sterol - health concern. ("Steve Alexander")
  Pitching Rates (Amber/Bruce Carpenter)
  Cylindro-conical Plastic Fermenters ("Eric L. Peters")
  Refrigerating beer / constant aeration of starer / survival rates of stored yeast / Hot Side Aeration ("George De Piro")
  Stirring starters (Domenick Venezia)
  Oatmeal Stout ("charles beaver")
  Hop growing question (Denis Barsalo)
  glass carboy ("Darren Robey")

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---------------------------------------------------------------------- Date: Sat, 29 Aug 1998 09:12:40 -0400 From: AJ <ajdel at mindspring.com> Subject: Alkalinity/Modes and Nodes/Tannin in Cyser/Stirring >From Lou: Heavner >if you are not going to explain them, it might be easier to >just say "multiply the alkalinity by 1.22." Ah yes. Good point. Alkalinity in ppm as CaCO3 is 50 times the alkalinity in milliequivalents per liter, i.e. the number of milliequivalents of strong acid, required to bring a liter of the water to pH 4.3. One milliequivalent of acid is required for each milliequivalent of bicarbonate present (H+ + HCO3- --> H2CO3). The equivalent weight of bicarbonate is 61 mg/mEq. * * * * * * * * * * * * * * * * * * * * * * * Not that it really matters that much to brewers but I think Mark T A Nesdoly may be confusing "nodes" and "modes". A node is a place where the E-field is 0 (or nearly so). Where the nodes occur depends on the configuration of the cavity which determines the mode of propagation within it. The purpose of the mode stirrer is to change this configuration thus changing the mode and moving the nulls (nodes) around. * * * * * * * * * * * * * * * * * * * * * * * * * Jebbly suggests adding raisins to mead musts to obtain a tannin taste. I guess I'm confused as to why anyone would want to do this though I've seen it suggested that grape tannin be added to meads. I've got a cyser with polyphenols at 90 mg per liter and a sack at 16 (these represent the totallity of my mead making BTW). These were made at the same time (back in Jan) from the same honey. No tannin was added. The cyser is just plain phenolic rough! The sack is lovely. Will the cyser mellow with time? Is the mellowing the same as in beer, i.e. complexing and precipitation of the polyphenols? If so, why put it in in the first place? * * * * * * * * * * * * * * * * * * * * * * * * * * Stir plates benefit growth in starters by keeping the yeast in suspension and thus bathed in the nutrients of the broth. This is so whether they are in growth or fermentation phase. Clearly, external oxygen must be supplied or, as the other posters have observed, the broth will simply become blanketed with CO2. Mark Bayer asked how yeast would grow if an airstone supplying air or O2 were in the broth and the broth on a stir plate. The answer here is that the froth formed by the airstone would make a horrible mess. The oxygen or air needs to be supplied periodically in order to allow the foam to subside or an anti-foaming agent must be used. Dreamers may consult the Cole - Parmer caltalog under "Fermenters" where devices costing as much as a good used car are touted. These consist of a vessel with a stirrer equipped with pH, DO and foam sensors connected to devices which meter O2, buffers and antifoam into the vesses as required. This obviously represents the ultimate but I expect the innovative could kluge up arrangements equally as effective. My thoughts along these lines have been to use a small inverted carboy (they used to sell or perhaps still do a doodad that caps them upside down) with an airstone connected to an O2 bottle hooked to a timer and valve that would provide multiple short bursts of O2 every 10 minutes or so. I think that the agitation produced by the gas bursts might be enough to keep the cells in suspension to the point that a stir-plate wouldn't be necessary. Another thought is to use a stir plate with a flask hooked to an aquarium pump in such a way that the air stream does not pass through the broth but just sweeps out the CO2 released. In this case exchange through the surface of the liquid would be enhanced by the stirring. Return to table of contents
Date: Sat, 29 Aug 1998 09:40:53 -0400 From: "Steve Alexander" <steve-alexander at worldnet.att.net> Subject: yeast models/amino acids/sterol - health concern. Jim Liddel wrote ... >The Ramirez articles in >JIB and B and B read this way. "maximum alcohol in minimum time", >"industrial brewing". And they used 16 P wort. I have access to the JIB article only at the moment, they do not spec the SG anywhere in the article. The abstract of "A FLAVOUR MODEL FOR BEER FERMENTATION" reads: " A new beer fermentation model is developed based on fundamental knowledge of biochemical pathways. The model can be subdivided into a growth model, an amino acid model and a flavour/aroma model. Experimentation allowed for accurate model parameter identification. The results demonstrate the capability to accurately accurately describe batch beer fermentation dynamics." This paper is decidely about modeling the important yeast parameters in terms of uptake and byproducts. It is not about maximum alcohol, minimum time and there is no mention of these factors. This paper is the successor to papers like Ayrapaa, Nordstrom and to 4 decades of chemostat experiments by guys like Young and others -tho it's more about modelling the fermentation and deriving valid math representations rather then uncovering new pathways. Basically they propose a set of equations to model quite a few beer parameters - sugar & amino uptake, specific esters, fusels, VDKs. They then run batch fermentations at several temps measuring these parameters and use the data to create coefficients for the model. The resulting model curves match the real data quite closely indicating that there is something right about the model equations. The coefficients only apply to the given yeast, and the other undescribed wort parameters - so the specific number aren't important. That the model works so well is important and tells us that the equations do describe, isobutanol production for example quite accurately in terms of yeast mass, yeast specific growth and valine concentrations. >My point is that this is >research that is geared, as is most beer research. towards making light >lager in 900 barrel batches 24 hours a day 7 days a week. So what ? Are you saying the model doesn't apply ? On what basis ? The biochem equation date back to Ehrlich and Ayrapaa from the 1906-1970 and have been verified in a number of ways and under many conditions. To my non-professional eye almost all of the terms derive from simple kinetic models or from the Michaelis-Menten model that described enzyme catalysed reactions. What do you propose is different in HB that invalidates the result ? As far as I'm concerned a negative finding, that the curves didn't match would indictate the the model was incorrect or incomplete. One can still argue that the discrepancies between model and data represent an imperfect model, and also measurement difficulty. Some of the VDK models for example are "weak" IMO. Still the result must be considered an impressive demonstration that certain biochem pathways have been successfully accurately modeled. >Granted some of >their stuff is valid but Ramirez, based on his CV is not a brewing >scientist. he is into modeling and process control. The authors are from the Chem.E. dept, but the model is of yeast, not an industrial fermentation operation - tho' there is clearly cross applicabilty. The model describes how yeast work. This is a necessary prereq' for process control, but that subject is not discussed in this paper. As for the "some of their stuff is valid" comment. I guess this means you have evidence to refute parts of it. Would you care to describe what is in error and give a citation ? I'm not arguing that Gee and Ramirez 1994 paper is the last word on the issue, nor that their model represents a perfect fit to the data , but the authors don't claim this either. To dump on a peer reviewed journal article, particularly one so recent, without any description of why or reference is bogus IMO. Perhaps you have a good reference refuting points - if so I'd sincerely like to hear about it. Otherwise it's you opinion versus the IoB, and I'm afraid I'll have to side with reviewed literature from a highly respected institute. Lou.Heavner at frco.com asks ... > BTW, that wouldn't be Fred Ramirez of CU in boulder, would it? Yes it is. W.Fred Ramirez and Douglas A.Gee both of UofC Boulder wrote the article in late 1993. - -- Where to get valine, leucine, isoleucine. I'm not seriously suggesting this (yet) but the idea is that at higher concentrations these can reduce levels of n-propanol, isobutyl alc., 2-methyl-1-butanol and isoamyl alc. perhaps despite underpitching. It may also reduce levels of phenyl-alcohols such as tyrosol, tho' this is not covered in the paper above. You can get these at health food stores as well as chem supply houses - not cheaply tho'. - -- IMPORANT WARNING: Jim Liddel mentioned the addition of ergosterol as a yeast growth supplement. Ingestion of chalciferous ergosterol (vitamin D) can cause liver and CNS problems and corneal opacity at continued ingestion rates of 1mg per day. Yeast growth might require 4mg/L to replace normal O2 levels so as you can see seeding your wort with high levels of sterol might cause serious health problems to the consumer if the yeast fail to remove the sterol. This may be a useful starter technique, particularly if you (as Jim does) remove the supernantant 'beer' before pitching. Tho' as Jim pointed out privately - "air is cheap". Also sterol addition alone doesn't satisfy the UFA req of yeast. Steve Alexander Return to table of contents
Date: Sat, 29 Aug 1998 09:33:01 -0500 From: Amber/Bruce Carpenter <alaconn at arkansas.net> Subject: Pitching Rates Hello, I have a couple of questions for the group concerning pitching rates. First, a little info. My current procedure is to start with a Wyeast suited for the style of beer I plan to brew. I create a starter based on nutrient pack instructions. I then add to this starter the two small packs of dry yeast included in the beer kit I have purchased. The main reason I add the dry yeast is due to the extensive discussion about underpitching and that some believe that 1 package of Wyeast is not enough yeast. And after all, the dry yeast comes with my beer kit, so it is no extra expense. Questions: 1. Does this procedure have any striking advantages or disadvantages? 2. Am I "adulterating" my beer with 2 types of yeast and violating a purist's code? The musings of a newbie, thanks for any help. Email welcome. Bruce Return to table of contents
Date: Sat, 29 Aug 1998 09:26:42 -0500 From: "Eric L. Peters" <E-Peters at csu.edu> Subject: Cylindro-conical Plastic Fermenters Please excuse me if this topic has been discussed to death, but I am interested in upgrading my brewing setup, and I am curious about the cylindro-conical fermenters that I have seen advertised. One (the Conical II) is sold by South Bay Homebrew Supply, and the other by Mini-Brew Systems. Does anyone have experience with either (or both) of these? Are they worthwhile (I am primarily interested in them because of their apparent usefulness in trub removal and the ability to transfer without siphoning. I am less interested in harvesting yeast)? If so, any opinions on which system is better? TIA Eric Peters mailto:E-Peters at csu.edu Return to table of contents
Date: Sat, 29 Aug 98 10:49:46 PDT From: "George De Piro" <gdepiro at fcc.net> Subject: Refrigerating beer / constant aeration of starer / survival rates of stored yeast / Hot Side Aeration Hi all, Lou noted that my recent list of things that are bad for beer did not include warm storage of finished beer. I knew I forgot some important stuff. I'm sure there's much more. It is second nature for me to keep finished beer cool. It is incredibly important. Before I expanded my refrigerated space I would ice kegs for serving only. The beer got pretty bad pretty fast at >78F (25C). Over a few weeks you may be OK at summertime room temperature IF you avoided things like oxygen pickup and microbial contamination, but those are two big "ifs." Some beers do well if kept at 50-55F (10-12.7C), particularly bottle-conditoned strong beers or some of the more complex-tasting styles. That temperature range should be the maximium, though. I keep lagers at 36F (2.2C) (and most of my ales, too). The higher the temperature, the faster all the chemical reactions in beer will occur. Staling will definitely occur in a much shorter time. Note: this is another one of those rare times where the word "always" is appropriate. - --------------------------------------------------------------------- Mark (and others) ask about constant aeration and stirring of the starter. Mark specifically asks if an aquarium pump can be used to aerate the starter while stirring. Yes, it most certainly can. The use of a 0.2 micron filter will ensure sterility of the air. One warning, though: the yeast MUST have a food source during aeration or they will start to use up their glycogen. Don't constantly aerate if you can't feed them regularly. Stirring the yeast not only helps reduce CO2 levels in the liquid, it helps keep the yeast suspended. This allows them to do their work faster. - --------------------------------------------------------------------- Charley asks about how long yeast can survive in cold storage under wort. At Siebel we were told to use your yeast within a week. I checked this at home. I had two strains (Wyeast 2206 and an ale starin that I don't recall). I had been keeping them both at 36F (2.2C) and feeding them fresh wort every two weeks. Staining with methylene blue showed ~50% of the cells picking up the stain after about a month. That's bad. Pitching a yeast cake in that condition will actually provide more live cells than most homebrewers pitch, but you will also be pitching many dead cells (that can give a yeasty off-flavor to the beer) and the live cells probably aren't at their best. You can pitch them (I have done this), but be aware of what the effect may be on your product. - -------------------------------------------------------------------- There has been some talk about Anchor Brewing and HSA in their process. They are not the only brewery that recognizes this as a problem for their beer. Deschutes (Bend, OR) had (in Jan. 1996) a whirlpool tank with a welding defect that caused aeration of the hot wort. The brewer told me that this was the biggest factor limiting the shelf life of their beer (I specifically asked about the shelf life of their product). As I said before, HSA is not the worst thing on the planet, but it is not good. It is also one of the single most simple things to avoid, so why design your system without taking it into consideration? I'm not saying to work in an inert atmosphere, but when faced with the question, "Should I let the hot wort drop 2 feet from the lauter tun outlet into the grant or buy some extra tubing?" the answer should be obvious! Have fun! George de Piro (Nyack, NY) Return to table of contents
Date: Sat, 29 Aug 1998 08:00:55 -0700 (PDT) From: Domenick Venezia <demonick at zgi.com> Subject: Stirring starters Riedel, Dave" <RiedelD at PAC.DFO-MPO.GC.CA> asks: >> In HBD #2807, Hugh Hoover asked: >> Stir plates. There are repeated assertions that they increase >> the available O2, which increases the health & growth of the yeast. >> Ok, but riddle me this... After fermentation starts, and a CO2 >> blanket covers the yeast, how does the stirring improve oxygenation? >> ... > So far as I've noticed, no-one responded. I'd like to know what the > consensus is on this, as I like the idea of the stir-plate as a cost > effective and simple alternative to direct oxygenation of starters. Does > the agitation encourage yeast growth? By stirring the wort, you > should create enough disturbance in the vessel to disrupt the C02 > blanket, but I would think this only applies until the point at which > the C02 has forced all of the air out of the fermenter. As the fermentation vessel (flask) is unsealed, but plugged with cotton or filter, simple diffusion would help to keep some O2 in the flask. Stirring also disrupts the CO2 blanket and increases the rate of O2 diffusion into the flask. The agitation also keeps all the yeast cells suspended and in contact with all the nutrients in the media. Without agitation local nutrient voids can be created in the media by particularly active cells. These could be voids of any rate limiting nutrient. Natural diffusion would tend to fill these voids slowly, but if the active cells are metabolizing faster than diffusion can replenish the supply the void would remain. "Starved" cells flocculate, so some cells may drop out of solution (the best and brightest) prematurely in response to purely local conditions. By stirring, these cells are always presented with what they need and can continue to grow swiftly until all the nutrient(s) in the entire flask are consumed. I would think that in this way stirring helps select for the most active yeast cells. Domenick Venezia demonick at zgi dot com Return to table of contents
Date: Sun, 30 Aug 1998 13:13:42 -0500 From: "charles beaver" <cbeav at netnitco.net> Subject: Oatmeal Stout I am contemplating making an oatmeal stout in the next few weeks. As a veteran single step infusion masher I and wondering if it is a *mandatory* that I include a protein rest. Any opinions are welcome. Thx Return to table of contents
Date: Sun, 30 Aug 1998 14:44:29 -0400 From: Denis Barsalo <denisb at cam.org> Subject: Hop growing question Hoppers, Given two vines of equal size, which one would grow larger, fatter cones? Cascade or Perle? Denis Barsalo Return to table of contents
Date: Mon, 31 Aug 1998 13:07:22 +11:00 From: "Darren Robey" <robeyd at vida.agvic.gov.au> Subject: glass carboy Dear brewfolk. I have ben given a 5 gal galss carboy, but there is 1 problem. It has a round outles in the bottom. What sort of bung would I use to stop this that wouldnt taint the beer. would ruber or cork etc be useful? Cheers Darren Return to table of contents
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