HOMEBREW Digest #4328 Thu 21 August 2003

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  Aluminum vs Steel tanks (John Palmer)
  flashlights and beer (Bob Devine)
  Re: Do levels (Cairns Jim MTPROUS)
  Sanitizers and Septic (rickdude02)
  Gump and knowing it all ("Dave Burley")
  How much priming sugar per bottle (Bob Pelletier)
  Re: Dried Hops ("Jerry Zeidler")
  Exploding CO2 tanks ("Keith Lemcke")
  Re: Sanitizers and Septic ("Rob Dewhirst")
  Starter Strategies ("Martin Brungard")
  RE: anti-foam (Brian Lundeen)
  Re: Munton's Wheat DME (Robert Sandefer)
  Dr. Cone Responds-Conical Fermenters & Harvesting Yeast- Bob Fawbush ("Rob Moline")
  Dr. Cone Responds-Metabolism (follow up)-Fredrik ("Rob Moline")
  Dr. Cone Responds - Aerobic yeast starters- Fred L Johnson ("Rob Moline")
  Dr. Cone Responds - Attenuation- Dave ("Rob Moline")
  CO2 Tanks ("Tanksalot")
  Re: The reason for the seemingly excessive oxygen requirements? ("-S")

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * The HBD Logo Store is now open! * * http://www.hbd.org/store.html * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Beer is our obsession and we're late for therapy! * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * IN PROGRESS! * * * * * * * * * Dr. Clayton Cone Fortnight of Yeast * * 8/11/03 - 8/22/03 Yeast Questions Answered * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Send articles for __publication_only__ to post@hbd.org If your e-mail account is being deleted, please unsubscribe first!! To SUBSCRIBE or UNSUBSCRIBE send an e-mail message with the word "subscribe" or "unsubscribe" to request@hbd.org FROM THE E-MAIL ACCOUNT YOU WISH TO HAVE SUBSCRIBED OR UNSUBSCRIBED!!!** IF YOU HAVE SPAM-PROOFED your e-mail address, you cannot subscribe to the digest as we cannot reach you. We will not correct your address for the automation - that's your job. HAVING TROUBLE posting, subscribing or unsusubscribing? See the HBD FAQ at http://hbd.org. The HBD is a copyrighted document. The compilation is copyright HBD.ORG. Individual postings are copyright by their authors. ASK before reproducing and you'll rarely have trouble. Digest content cannot be reproduced by any means for sale or profit. More information is available by sending the word "info" to req at hbd.org or read the HBD FAQ at http://hbd.org. JANITOR on duty: Pat Babcock (janitor@hbd.org)
---------------------------------------------------------------------- Date: Tue, 19 Aug 2003 21:56:58 -0700 From: John Palmer <jjpalmer at altrionet.com> Subject: Aluminum vs Steel tanks Sorry, I missed the earlier question, just saw Rama's reply today. The thought seems to be that aluminum tanks are more dangerous or prone to failure than steel tanks, and the reason given was that aluminum was more brittle than steel. Mostly true. This is a bit of a trick question, it's like picking any dog to fight any cat, ie. the outcome is going to depend on the breed. Same with the aluminum and steel alloys. Pure aluminum is much more ductile than iron or steel, but it is much weaker too. To make a tank out of aluminum, you have to alloy it with magnesium, silicon, mangenese, etc. to bring the strength up, and in the forming process you cold work it a lot to raise the strength even more, and yes it does get more brittle. Meanwhile, plain carbon steel is so cheap that you can afford to make a heavy tank out of it. I should also mention that tanks are designed to Leak-before-Burst, i.e., they shouldn't fail catastrophically if they develop a crack. Of course if you shoot one with a bullet then all bets are off. Carbon steel's perceived ductility and fatigue resistance has more to do with the lack of alloying elements than the presence of carbon. Aluminum, to achieve useful strengths, has more alloying elements to stiffen the crystal structure, with the net result being that it work hardens faster than carbon steel. I am just scratching the surface here, but I have a feeling that I would post more than anyone really cares about. One final thought is that the fracture toughness of steel is higher than that of most aluminum alloys, so that steel tanks can take more abuse than aluminum tanks without failure. John Palmer john at howtobrew.com www.realbeer.com/jjpalmer www.howtobrew.com - the free online book of homebrewing Return to table of contents
Date: Tue, 19 Aug 2003 23:40:53 -0600 From: Bob Devine <bob.devine at worldnet.att.net> Subject: flashlights and beer Eric <edahlber at rochester.rr.com> asks: > Also, I know the phenomenon we call beer skunking is a result > of light and hop oils reacting, but I am wondering if my nightly > ritual of shining a flashlight into the carboy may be having any > negative effect on my yeast? Photosensitive yeast? Ahhh, the old Heisenbeer Uncertainty Principle. All homebrewers go through this phase of checking on their beer to an, almost, obsessive level. After all, if you aren't checking on the beer, maybe it is not doing anything! Seriously, the skunking effect comes from ultraviolet light hitting and breaking isohumulones which, when combined with hydrogen sulphide or other thiols, creates an organic compound, mercaptan, that is detectable in the parts-per-billion level. Unless your flashlight produces a lot of light in the ultra-violet range (fluorescent lights do cause skunking), you should be safe. But even if your flashlight produces only visible light, the violet portion may cause skunking if a "sensitizer" such as riboflavin causes more of the thiols to be formed. Check back through the HBD archives for a paper reference. Best to keep the fermenting beer in a dark spot. Bob Devine Return to table of contents
Date: Wed, 20 Aug 2003 09:53:19 -0400 From: Cairns Jim MTPROUS <Jim.Cairns at mt.com> Subject: Re: Do levels Date: Tue, 19 Aug 2003 12:20:27 +0000 From: "A.J. deLange" <ajdel at cox.net> Subject: DO Levels AJ wrote: I never really fully accepted the thesis that DO levels attainable at a particular partial pressure were a strong function of the strength of the solution Finally! A subject I know well. Lol All DO meters measure O2 differently. However, the majority of them use a Clark Polarographic cell and base the measurement on Henrys Law of Pressure. Basically, Henries law states that the partial pressure of O2 in air should be the same as in a liquid. But, it's a little more complicated than that. There are many other factors that have to be accounted for to really determine DO content. Temperature, salinity, membrane permeability, the medium just to name a few. Plus, to cloud the measurement up just a little more, all meters use the concentration curve of pure water. Keep in mind most of these factors are for determining the concentration.(PPM/PPB) Concentration is very difficult to determine. Saturation (0%-100%) measurements are much more forgiving. Soooo...having said that, you're right. There are a lot of factors that have to be taken into account in order to make an accurate DO measurement. So many, that using this method is not a practical way for determining the DO concentration of any given medium. Sincerely, Jim C. jim.cairns at mt.com Return to table of contents
Date: Wed, 20 Aug 2003 06:44:42 -0400 (GMT) From: rickdude02 at earthlink.net Subject: Sanitizers and Septic Not to worry-- two factors prevent your use of sanitizers from blocking proper operation of your septic tank. The first is simply the sheer volume of water and waste that goes into your tank as compared to the amount of sanitizer. IOW, the sanitizer is too dilute to have an impact. The second is that soil (sewage, waste, etc.) deactivates just about any sanitizer, which is why you should always sanitize clean items rather than dirty. (Acid based sanitizers can withstand the deactivation, they just aren't that effective in penetrating soil.) Rick Theiner LOGIC, Inc. Return to table of contents
Date: Wed, 20 Aug 2003 10:00:32 -0400 From: "Dave Burley" <Dave_Burley at charter.net> Subject: Gump and knowing it all Brewsters: Gump says he refuses to call me to inform me that he doesn't know it all. At least that's what I think he meant. {8< ) Keep on Brewin' Dave Burley Return to table of contents
Date: Wed, 20 Aug 2003 10:13:22 -0400 From: Bob Pelletier <rp at ihrsa.org> Subject: How much priming sugar per bottle I keg most of my beer but I need to bottle a few entries soon and was wondering how much sugar I should add to each 12oz bottle. The beers are a porter, a kolsch and a wheat. TIA, Bob Return to table of contents
Date: Wed, 20 Aug 2003 13:31:51 -0400 From: "Jerry Zeidler" <gjzeidler at suscom.net> Subject: Re: Dried Hops David King wonders how others dry, package and store their homegrown hops. When I harvest my hops, I lay the cones on a screen, which I lay on a tabletop in a well-ventilated room with the shades drawn. It's not really dark in there, but there's no direct sunlight hitting the cones. I allow the hops to dry at ambient temperature for 24-36 hours, then turn them and air-dry them for another 12-24 hours, or until the stems in the cones are beginning to get brittle. Once dry, I stuff 2 oz. into a sandwich-sized zipper-close baggie (takes some squashing and cramming). I seal the baggie most of the way across, then set the bag on a countertop and squash it further with a book or other large, flat surface, then close the zipper seal with the weight still bearing on the bag. This is to purge as much air out of the bag as possible. Once sealed, I wrap the baggie in freezer wrap to prevent light exposure. This double-wrapped package is then labeled with the type of hops and the date packed, then placed in the chest freezer until brewing day. I know that my method of "purging" air from the bags is imperfect, but I have not had any reason to go to any further effort or expense, since my I have always used my hops (or given them away) before they have had a chance to go stale. Jerry Zeidler Williamsport, PA Return to table of contents
Date: Thu, 21 Aug 2003 00:46:49 -0600 From: "Keith Lemcke" <klemcke at siebelinstitute.com> Subject: Exploding CO2 tanks Great thread on CO2 tank safety. I hope any & all service establishments who change CO2 tanks frequently will eventually move to bulk CO2 storage, which uses a lower pressure stationary CO2 tank that is filled from a bulk truck right at the service environment. This completely eliminates the need to move tanks, which aside from the rare explosive incident, saves tank handlers from injury. Watching big CO2 bottles get moved around, especially up and down stairs, has always been an uncomfortable thing, and I am sure there are a lot of injuries attributable to CO2 bottle handling every year. Keith Lemcke Draught Beer Guild Return to table of contents
Date: Wed, 20 Aug 2003 13:23:23 -0500 From: "Rob Dewhirst" <rob at hairydogbrewery.com> Subject: Re: Sanitizers and Septic >Does anyone have information on using > sanitizers and it's effect on the septic system? I'm hoping that the > relatively small amounts I use for five gallon batches once a month or so > shouldn't be too detrimental. I do not have some sort of authoritative study where people threw iodophor in their septic system and studied the results, but it's pretty easy to see the scope without even crunching the real numbers. If you are mixing iodophor to taste-free sanitizing levels, and then pouring that dilution into a septic tank of several hundred gallons, you are again diluting this so low that the few organisms you might kills off will regenerate within minutes, if not seconds. Same applies for bleach. Just use common sense and don't go overboard. Return to table of contents
Date: Wed, 20 Aug 2003 14:50:30 -0400 From: "Martin Brungard" <Martin.Brungard at trow.com> Subject: Starter Strategies The responses to the question of how to best grow yeast starters were encouraging. The guidance was welcome and it has created more thought on my part. It seems fairly clear that constant wort feeding is preferable to incremental feeding in order to avoid the Crabtree Effect. It took a little digging to figure what the Crabtree Effect was, but it seems that it's the phenomena of the yeast producing alcohol, regardless of wort oxygen content, when the glucose level exceeds 0.4 percent. Steve Alexander indicated that using a 7P or lower malt wort will keep the starter below 0.4 percent. I'm pretty sure that White Labs said they use a 5P malt wort for their production. Steve suggested that if you set up a starter with constant wort feeding, you would need to avoid overfeeding and underfeeding the starter, matching the dosage with the yeast growth. Steve suggests that you would have to monitor the CO2 and ethanol production to gauge the dosage rate. I did a little research and found a reference in Vol 62, #2, of the ASBC Journal that suggests that yeast do OK in an aerobic condition even when nutrients are limited. So it seems that the only thing we really need to watch is overfeeding. This may substantially reduce the sensitivity of the dosage rate. I'm sure some smart person can probably calculate a dosage rate with respect to initial cell concentration and wort strength. It's not me! Jeremy Bergsman brought up another interesting idea for wort starters, oxygenating the wort by storing it in an oxygen-filled pressure vessel. He suggested creating a PVC or other type of container, but the obvious container is a corny keg. As I understand it, this is similar to a Zahm and Nagel tank that George Fix used to mention. Jeremy hypothesized that the added wort would be thoroughly oxygenated as its added to the starter, but I don't think that the minor volume of oxygenated wort dosed into the starter would be sufficient to keep the starter aerated. So, continuous aeration would still be needed. But, his idea does have several merits. The pressurized wort would make it easy to meter wort into the starter with a needle valve. The use of a corny keg also means that you could just pour the freshly boiled wort without cooling into the corny and seal, hopefully offering less infection risk. The most important merit I see is the toxic effect against infection that superoxygenation could provide the stored and pressurized wort. Does anyone know what oxygen concentration would be needed to create a condition lethal to most spoilage organisms? I think A.J. DeLange and George Fix did studies of oxygen concentration in wort, but those apparently were at atmospheric pressure. We could use some information on equilibrium oxygen concentrations under various pressures and wort gravities. Anyone up for that? Another drawback may be the effect of long-term oxygenation on raw wort. Would it degrade somehow? Wow, think of what a time savings you could get if you could keg a batch of starter wort and have it keep for several months without infection. Is it possible? I have to say that there are some interesting and potentially practical starter strategies forming here. What are your thoughts? Martin Brungard Tallahassee, FL Return to table of contents
Date: Wed, 20 Aug 2003 10:54:39 -0500 From: Brian Lundeen <BLundeen at rrc.mb.ca> Subject: RE: anti-foam > Date: Tue, 19 Aug 2003 06:08:43 -0400 > From: "Kevin Kutskill" <beer-geek at comcast.net> > Subject: Re: Room enough for 10 gallons? > > > Like Jeff Renner mentioned, there is a product called Foam > Control, sold by Hop Tech (no affiliation, yada, yada, yada). > You use 1 tsp. for every 5 gallons, and works like a dream. Hop Tech must love you if you are using it up at that rate. I found 1/4 tsp of their product was lots, sometimes all it took was a few drops. It depends largely on the wort and yeast. I've switched to FermCap now. Picked up a lifetime supply from a defunct brew pub for a pittance. That does remind me of a question. Being a commercial brewery product, one can assume FermCap is used largely in enclosed, vented kettles. Are there any safety issues with having this stuff boiling in a homebrew kettle that is filling up the air in your house or garage with the steam? I've noticed I get a bit of a headache during the boils now, and wonder if it's from some volatiles coming off from this stuff? Cheers Brian, brewing in Winnipeg Return to table of contents
Date: Wed, 20 Aug 2003 16:45:46 -0400 From: Robert Sandefer <melamor at vzavenue.net> Subject: Re: Munton's Wheat DME David, My supplier has told me that Munton's wheat dme is a 60:40 wheat:barley blend, if my memory serves. Hope this helps. Robert Sandefer Arlington, VA Return to table of contents
Date: Wed, 20 Aug 2003 21:08:03 -0500 From: "Rob Moline" <jethrogump at mchsi.com> Subject: Dr. Cone Responds-Conical Fermenters & Harvesting Yeast- Bob Fawbush Dr. Cone Responds-Conical Fermenters & Harvesting Yeast- Bob Fawbush Hi Dr. Cone, Recently many homebrewers have purchased or fabricated conical fermenters that employ 60 deg sloped sides & a bottom dump port. My questions are as follows: 1)Assuming normal yeast fermentation temperatures are employed - How many days of fermentation should occur before a brewer dumps yeast for reuse ? 2)Will the pressure that builds up on the condensed yeast cake at the bottom of the conical fermenter over the fermentation cycle damage or harm future harvested yeast? If so how ? Thank you for taking the time to answer my questions. Cheers! Bob Fawbush Bob Fawbush, The conical bottom fermenters are neat. (1)Attenuation time depends on yeast strain, yeast health, wort gravity, mashing protocol and fermentation temperature. The yeast should not be settling appreciably until the end of the fermentation when all the sugar has been used up (attenuation). Then it begins to flocculate and settle out. The rate of settling is strain dependent, final gravity and how long and well you have stored the re-pitched yeast. You should note the fermentation activity, CO2 bubbling. When the CO2 bubbling dramatically slows down and you are near or at final gravity the yeast begins to settle; three to five days depending on the temperature of fermentation; three days at 80F, five plus days at 60F. These are very broad suggestions. Be guided by the turbidity of the wort. If you can refrigerate the mash, the yeast will settle faster and you can begin to remove the settled yeast. Refrigeration places less stress on the yeast to be used for the next pitching. Some beer makers will remove and discard the bottom 1/3 of the settled to get rid of most of the trub to minimize the carry over in the next re-pitching. The remainder should be removed ASAP and refrigerated at <4C. if possible. I wish there was a more definitive answer. (2) CO2 should present no problem in the fermenter size that the average home brewer would use: CO2 at 0.2 atmospheres pressure stimulates yeast growth. CO2 at 0.5 atmospheres pressure begins to exert a negative effect on yeast growth. CO2 at 3.0 atmospheres pressure stops growth CO2 at 3.0 atmospheres pressure does not stop fermentation-alcohol production. 10 ft. height fermenter = 0.3 atmospheres. Clayton Cone - --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.512 / Virus Database: 309 - Release Date: 8/19/2003 Return to table of contents
Date: Wed, 20 Aug 2003 21:08:05 -0500 From: "Rob Moline" <jethrogump at mchsi.com> Subject: Dr. Cone Responds-Metabolism (follow up)-Fredrik Dr. Cone Responds-Metabolism (follow up)-Fredrik Dear Dr.Cone and Tobias! Thank you very very much for answering all the questions!! :) :) Your answers gave me some very valuable ideas how I need to revise and extend my thinking on these topics! I sure hope I am not beeing rude by asking too many questions considering the limited bandwidth!? But If there is still space left at the end of this two week period , I do have a couple of follow up questions. (Lage phase and glycogen) 1) If there is basically no matebolic activity during the lag phase - is the glycogen level not an issue during the lag phase? I had the impression that low glycogen levels (like in stored yeast?) would cause an extended lag due to some "free energy limitation"? I thought that until yeast start to uptake and metabolise sugars, glycogen (and some others) was the energy supply for whatever activites that is going on at this time? It this wrong? Are all the adaptations in the lag phase of passive nature, like equalizing gradients? requiring no metabolic energy to be spent? I understand that choice of strain may impact the lag time, but for any given strain, what would be the most important factors and variables be that determines the length of the lag? (sugar utilization) 2) From your answer about sugar utilization, to make sure I got it right, did I understand things correct if I think there is no regulation of sucrose uptake and invertase activity due to external glucose? so they would both start at the same time and go on in parallell? If, as like I would guess(?) that glucose uptake is alot quicker than sucrose uptake, would it be possible to observe a small dip in CO2 production activity at the point where the external glucose is consumed or reached soem treshold? I did observer such a dip in a test I did. It sure is possible that ambient conditions cause this, but in this case for some reason I think not, and the dip coincidently occured at about 6% depletion of fermentables. I would like to ask you about your opinon if you think that detecting such a dip (about 1.5 hours long and the "dip" was lowering the CO2 rate by some 15%) is possible? Or do you think I should rule this explanation out and start looking for another explanation of the dip? /Fredrik Fredrik, Thanks for probing a little further into my reply to your question. (1) You are correct in your impressions. Perhaps I overstated the lack of metabolic activity during the lag phase. While it is acclimating itself to its new environment, it is still very much alive and requires energy. This energy does come from the glycogen and trehalose reserve present in the yeast from the last fermentation cycle and left over from the refrigerated storage period. If this carbohydrate reserve has been consumed during poor and or extended storage, there will be an extended lag phase. (2) Perhaps I should explain the sucrose step a little better. Sucrose itself does not pass through the cell wall. Invertase is an external enzyme that is present at the beginning of the fermentation. It begins immediately to convert sucrose to glucose which joins with the initial glucose and inters through the cell wall together via glucose permease. There is no separate stage in which the initial glucose is used up, then the invertase begins to convert the sucrose to glucose. Glucose is a maltose inhibitor. Neither the permeases or the maltase are produced in the presence of >0.4% glucose. There is probably a short period before these enzymes get into full production. Also, the maltose inters the cell at a slower rate than glucose, so you would probably note a noticeable slowing down or dip in CO2 production for a short period of time. Yeast strain, wort composition, and fermentation temperature can effect this transition period. You were very observant. Keep in touch with future observations. Clayton Cone - --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.512 / Virus Database: 309 - Release Date: 8/19/2003 Return to table of contents
Date: Wed, 20 Aug 2003 21:08:04 -0500 From: "Rob Moline" <jethrogump at mchsi.com> Subject: Dr. Cone Responds - Aerobic yeast starters- Fred L Johnson Dr. Cone Responds - Aerobic yeast starters- Fred L Johnson Dr. Cone, Some of us (or perhaps only I) are attempting to culture our yeast starters in a respiratory state (with high oxygen and low glucose concentrations). In my experience, I cannot deliver very much air to the spinner culture using an aeration stone without creating too much foam. I have made several beers with poor head retention when I've included FermCap in the starter in sufficient quantity to prevent foaming in the aerated starter, so I've tried another method that does not require FermCap. I have been pumping filtered air at 2 liters/minute into the head space of a spinner culture with vigorous stirring. Questions: 1. Can pumping air into the head space with vigorous stirring provide sufficient oxygen to the yeast to maintain them in a respiratory state during incremental infusion feeding? 2. Can FermCap be used in aerated starters without detrimental effects on the beer? Fred L Johnson Fred, If your starter culture tank is 10 feet tall the answer is probably not. If it is several inches tall and a wide surface area, the answer is yes. A sterilized cotton plug should allow enough air transfer to the surface of a stirring wort culture to provide enough O2 for the yeast. Pumping a small stream of filtered air into the head space would help. I am not familiar with the composition of FermCap. Some antifoam compounds interfere with the oxygen transfer from the air into the wort media. Stirring via a magnet stirrer should minimize or eliminate any foaming problems. Clayton Cone - --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.512 / Virus Database: 309 - Release Date: 8/19/2003 Return to table of contents
Date: Wed, 20 Aug 2003 21:08:04 -0500 From: "Rob Moline" <jethrogump at mchsi.com> Subject: Dr. Cone Responds - Attenuation- Dave Dr. Cone Responds - Attenuation- Dave Dr. Cone, I have a situation where I switched from bottled spring water to tap water filtered through the 10" carbon filter, found at http://www.morebeer.com/ (FIL32), and my beer's attenuation has suffered, seemingly, because of the change. My attenuation levels for identical recipes went from 1.013 - 1.015 to 1.018-1.019. Increasing the amount of aeration and/or oxygenation at the start has no effect on the FG. Is there maybe a third cause I am overlooking, or can filtering water through a carbon filter change the water chemistry enough to alter the amount yeast attenuates the wort. Thanks for any information you can provide, Dave Dave, Water composition has a great effect on the mashing characteristics of wort and the fermentation characteristics of the yeast. Calcium and magnesium are the two key minerals. The water should contain 50-100 mg. of Ca+++/liter and 10-15mg. Mg+++/liter. Your tap water may be softer than the spring water. I would try adding 1/6 tsp. of gypsum and about half that amount of Epsom salts per gallon of water to be used for mashing. The calcium is needed to protect the starch conversion enzymes in the malted barley. Magnesium is needed in the yeast metabolic process. Let me know if it works. Clayton Cone - --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.512 / Virus Database: 309 - Release Date: 8/19/2003 Return to table of contents
Date: Wed, 20 Aug 2003 23:10:09 -0400 From: "Tanksalot" <tanksalot at rogers.com> Subject: CO2 Tanks CO2 tanks can be dangerous. The gas is compressed (to a liquid) under pressure approaching 1000 psi. But there is (or should be) a working Safety at the Tank Valve. This allows the gas to escape safely, but very noisily in the event of a problem at the valve end of the tank. If the Safety Valve blows, all the gas escapes and the tank cannot be refilled until the problem is corrected; most gas suppliers will simply replace the whole valve assembly as it is not practical to rebuild the Safety or "pressure relief". I live in Ontario, Canada and tanks are stamped so they must be hydrostatical tested every five years before they can be refilled. Two years ago I had some 2.5# and 15# tanks refilled, and foolishly left them in the trunk of my car for a few very-hot hours. It sounded like Vietnam as the Safety Valves in turn vented all of the gas and coated the trunk lid with "dry ice" ..even the last two tanks which I tried to cool with water. In this case it was an error by the welders' supply shop where they were overfilled. Larger tanks of course would be more of a hazard, but I don't believe there would be a "rocket" flying around your brewery. CO2 is the gas used in many fire extinguishers so it's not poisonous or flammable. Anyway, it is best to treat any compressed gas with respect! Larry at Tanksalot Return to table of contents
Date: Wed, 20 Aug 2003 23:36:43 -0400 From: "-S" <-s at adelphia.net> Subject: Re: The reason for the seemingly excessive oxygen requirements? Had to abbreviate for the 8kb limit but ... Curious Fredrik writes ... >Biomass(dry) is about 1% sterols (according to George Fix) >For simplicity I assume sterols = 100% ergosterol >squalene contains 0% oxygen >ergosterol contains 4% oxygen > >[...] O2 requirements for new healthy biomass >is 0.04% > >Assuming 100% utilization this indicated that a biomass yield of 10% on a 10 >plato wort would take no more than an initial oxygen level of about 3-4 ppm. Biomass growth is 5% according to Balling ... [ 200g maltose + 1 g ammonia -> 10g yeast + 97.5g EtOH + 93.6g CO2 ] Your 10P wort would grow enough yeast to require 2ppm of O2. *BUT* in normal brewing (not starters) you pitch about 10%-25% of this amount of yeast so it's a fraction of 1ppm for sterols. O2 utilization efficiency is obviously between 50% and 100% for each oxygen in sterol. >1) maybe there are other processes competing for the oxygen? If so which >onces? I've assumed that nonenzymatic reactions are not relevant in the >timeframe considered here, like in a starter, what do you think? More oxygen is required for the formation of unsaturated fatty acids(UFAs) than sterols. UFAs are extremely importantly wrt cell membrane properties. Several sources suggest that for air saturated wort (around 7-8ppm of O2) pitched with lipid depleted yeast that 10% of the O2 is used for sterol synthesis and 15% for UFA synthesis. I can't say exactly where the other 75% of oxygen is used, but the 'haem' protein is involved in the initial oxygen uptake for most yeast oxygen pathways. Respiration is one obvious use for O2. Also fresh wort is full of reducing substances capable and ready to oxidize at the drop of a hat. Fresh wort will chemically compound O2 saturation levels (~15ppm for pure O2) in a matter of several hours. Some of the O2 is lost to wort staling in a nonenzymatic way. In the mash the enzymes can use up saturation O2 levels in minutes if not seconds. In the fermenter the non-enzymatic staling processes require hours for the asme activity. >2) The rate of oxygen uptake is the limiting factor rather than the >absolute depletion of oxygen. Due to the diffusion kinetics [...] Oxygen induction is an active process regulated by several genes, not passive diffusion. Pitching levels of yeast can remove saturation levels of O2 in a matter of 20 minutes under the right conditions so uptake rate isn't the issue. >3) there is a waste of oxygen in the synthesis of ergosterol? Very likely, but I can't say how much. Yeast, like other cells, have very strong mechanisms for handling any free oxygen radicals that might result as 'waste'. >What is the proper way to resolve this confusion? I'd start with a good book. Dr.C.Cone mentioned a few. One I like a lot is "Brewing Yeast and Fermentation" by Boulton and Quain, 2001, ISBN 0-632-05475-1 >If the wort gets really really depleted of oxygen (=0 ppm), whayt the heck >is the oxygen used for? :). It seems from my crude estimations that it can't >all go into sterol synthesis? Are my estimates flawed? No - your estimate for sterol is a very good first step, but you neglected the other oxygen ereq - UFA and then again no one seems to know exactly where all the O2 goes besides respiration. >What did I miss? help! I think you didn't express your motive. It's interesting to note that yeast seem to consume some 3 or 4 times their minimum requirement of O2 and much of the excess beyond requirements goes to unknown destinations - but SO WHAT ! Yeast metabolism includes at least several hundred thousand reactions which are certainly not all understood quanitatievlyt in relation to each other. Why not start your search for understanding by considering which factors cause significant changes in brewing behaviour (flavor, fermentation, performance, flocculation and health) rather than try to hunt down the destination of every bit of every nutrient. The first task is merely very difficult, the second is almost impossible. The quant info simply does not exist. Great questions Fredrick - but it's time to use that library card and do some hunting through the technical literature. If I can help you with specific references or details, please let me know. -Steve Alexander Return to table of contents
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