HOMEBREW Digest #4626 Tue 12 October 2004

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  Artificial & other sweeteners: an overview (David Radwin)
  Fortnight Of Yeast, 2004 - stress vs biomassyield ("Fredrik")
  Kinetics and Thermodynamics, CCFC in Tazzie ("Dave Burley")
  Re: Pump Mounting ("Martin Brungard")
  Re: Curve Fitting (Christopher Swingley)
  FOY, 2004 -Response- Published attenuation levels for various yeasts- Fred Johnson ("Rob Moline")

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---------------------------------------------------------------------- Date: Mon, 11 Oct 2004 19:47:15 -0700 (PDT) From: David Radwin <dradwin at yahoo.com> Subject: Artificial & other sweeteners: an overview Related to some recent discussion, this article might be useful for anyone considering using Splenda, stevia, or various other sweeteners for beer or cider. It's informative but not especially detailed or technical. http://tinyurl.com/6p6fe or http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicl e/archive/2004/09/15/FDGA58M7L21.DTL David Return to table of contents
Date: Tue, 12 Oct 2004 06:51:28 +0200 From: "Fredrik" <carlsbergerensis at hotmail.com> Subject: Fortnight Of Yeast, 2004 - stress vs biomassyield Dr. Fischborn and Dr.Waldrop, thank you very much for hosting another fortnight of yeast! This is like Xmas for us. First I'm sorry to post so "long" and not very distinct questions but if I just made it short there may be misunderstandings, so I try to explain some of the motives and elaborate the questions. Your and everyone elses comments on these issues are much wanted!! I have some questions regarding yeast that just to set them in proper context are related to my attempt to understand yeast and make a computer simulation of a beer fermentation. I am currently modelling the states, active dormant and dead. And the transitions are considered by transition probabilites (statistically that is), and the transition functions are suppsoed to be state functions of yeast, wort and fermentor variables. The below question all relate to stress and biomassyield and to an extent the transition probabilites between states. I hope to decompose the stress into some principal stresses, and find how the depress the biomass yield (but also how they case damage and death, which is another side of it) Q1 -------------------------------------------------------------- Tracing back to Balling, many formulas in brewing, including alcohol/FG/OG formulas tend to assume a fixed biomass yield of some 5%. As I understand this is an empirically determined value, that I assume is an effective average under "typical conditions". But as far as I understand the biomass should be a dynamic and in an extended dynamic treatment I doesn't seem valid to treat the biomass yield as a constant? Stirplates in starters are but one example. Note: I am aware that respiration levels does increase the biomass yield too, but that is not what I am after here. I am trying to understand stress depression of the yield. Considering the biomass yield vs time, during a batch fermentation. Since stresses build up, and especially external sugars drop in the very end I am assuming that the biomass yield must drop during fermentation. For example, as the sugar concentration is low the rate of energy production drops. Actual Q1) How low is the cellwise biomass yield at EOF, just before the cells start to tend to go dormant? What do you think about the idea that the biomass yield drops to close to zero? What about correlating the transition from active to dormant with the biomass yield drop? The idea I have is that the biomass yield in turn would depend on the free energy balance. Incomes - expenses. Expenses also including possible stress factors, transport costs etc. If you feel this still is a dim question perhaps you can elaborate about the topics of dynamic biomass yield and biomass - stress correlation? Q2--------------------------------------------------------------- Actual Q2) In a normal batch fermentation, how would you rate these different factors that depress the biomass yield? : CO2, alcohol, concentration gradients on culture, UFA/sterol drop When using a stirplate but *not* aerate, what factor is most important beeing responsible for the increased biomass yield? i.e I want to if possible put numbers on how much the CO2 supersaturation depresses the biomasyield. etc. Have these things been quantified, and isolated from other stress factors? What if you stirr in an pressure gas chamber of high CO2 pressure, would the benefit from removal of gradient be significant still? Or is it some mechanical excitation of the cells? Q3 ------------------------------------------------------------ As alcohol tolerance are supposed to relate to pitching rates, sterol levels and also other add-on stress factors, I wonder what the conditions are for the alcohol tolerance numbers that you sometimes find for strain descriptions? It seems clear that there has to be a limit, but it also seems that the limit can be stretched? (ie it's not fixed) so the question is thus Actual Q3) How does yeast companies typically *define* the alcohol tolerance limit? ie. what is the exact experimental setup/conditions and numerial procedure used to arrive at the alcohol tolerance numbers? - ----------------------------------------------------------------- /Fredrik Return to table of contents
Date: Tue, 12 Oct 2004 10:54:23 -0400 From: "Dave Burley" <Dave_Burley at charter.net> Subject: Kinetics and Thermodynamics, CCFC in Tazzie Brewsters: /Fredrik is postulating that it is an energetic relationship as to why the maltotriose is the "last to be consumed". I doubt that and suspect it is a kinetic phenomenon, as are many of the cell wall transport phenomena and enzyme reactions. Perhaps part of the problem is /Fredrik's concept that somehow the yeast take in and consume carbohydrates serially. Not so. All the carbs are being processed in parallel. Some just more slowly than others. - -------------------- Stuart Grant is contemplating a CCF chiller to be used to withdraw his hot wort to his fermenter and worries if it will work by gravity. As far as working by gravity mine does just fine with a meter of height difference, but you may get some grief with the pelleted hops as I have in the past. Even with a Choreboy filter, the finely divided hops in combination with a high OG wort can slow down or even stop as it cools. Surely it is possible even in the Outback of Tazzie to mailorder some leaf hops to use as part of your hop charge. These leaf hops will act as a filter bed for the pelleted hops. Otherwise, I'd forget the idea based on my experience, unless you use a large diameter inner tube ( I think mine is 1/4 or 3/8 inch) on your CCF chiller. This will reduce your chilling capacity unless you use a longer tube to get the same total inner surface area as the smaller inner tube I use. Then again that cold tap water from near the South pole may do the job just fine with a larger diameter inner tube. Keep on Brewin' Dave Burley Return to table of contents
Date: Tue, 12 Oct 2004 07:13:39 -0800 From: "Martin Brungard" <mabrungard at hotmail.com> Subject: Re: Pump Mounting Mike O'Donnell posed a question about the mounting of a March mag pump. I work in the water and wastewater industry and deal with pumps frequently. Most motors are designed to work in a particular shaft orientation. The main reason that a motor needs to be oriented as intended is for bearing and shaft life. In the case of a horizontal motor, there is only limited provision for axial loading. Frequently, this is in the form of a couple of simple thrust washers. These washers are subjected to occassional contact with the rotor just to keep the rotor centered in the motor casing. When turned vertical, one of the thrust washers is subjected to constant loading from the rotor weight that will result in overheating and failure of the washer. In the case of a vertical shaft motor, the bearing system has been designed to support the constant axial load from the rotor weight. Usually, the motor is intended for only one vertical orientation, ie the motor can't be mounted upside down. Then the axial load would be placed on the bearing that wasn't intended to support an axial load. Its debatable if some vertical shaft motors can be used horizontally, but for the most part, they shouldn't be. I just checked the March website and confirmed that they specifically say that their pumps must be mounted horizontally. I have been into my March pump and can attest that they only have simple thrust washers at the shaft ends. They would not perform well in a vertical configuration. Martin Brungard Tallahassee, FL Return to table of contents
Date: Tue, 12 Oct 2004 12:23:32 -0800 From: Christopher Swingley <cswingle at iarc.uaf.edu> Subject: Re: Curve Fitting Greetings! * Martin Brungard <mabrungardathotmail.com> [2004-Oct-11 05:12 AKDT] * wrote: > One of the most widely known packages is Excel. Another is Grapher. > Both of these programs are commercial and somewhat expensive. Curve > fitting is not their main purpose. Neither of these programs do this > job very well. Agreed. > Fortunately, there is a cheap way to get a better solution. There is > a shareware product called CurveExpert that is specifically intended > for curve fitting. It does a very good job. Another good, and free choice is the 'R' statistical package. It is an open-source implementation of the 'S' statistical computing language, and is available for Linux, Mac System 8.6 - OS X, and Windows 95 or later. It is *certainly* more difficult to use than the program Martin mentions, but it is a full featured statistical package so it can do a lot more than just curve fitting. Consult: http://www.r-project.org/ for more information, and download locations for your platform. I've been using the program for the past year in an attempt to predict apparent attenuation using a bunch of variables (mash temperature, yeast type, starting gravity, and beer color). Here's a sample session demonstrating a linear fit to a bit of the data: > mashdata <- read.table('mash_temp_v_attenuation') > model <- lm(aa ~ sg, data=mashdata) > summary(model) Call: lm(formula = aa ~ sg, data = mashdata) Residuals: Min 1Q Median 3Q Max -7.3800 -2.1568 -0.0782 2.5637 7.9246 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 92.20718 5.05795 18.230 3.97e-12 *** sg -0.30051 0.08643 -3.477 0.00311 ** --- Signif. codes: 0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1 Residual standard error: 4.296 on 16 degrees of freedom Multiple R-Squared: 0.4304, Adjusted R-squared: 0.3948 F-statistic: 12.09 on 1 and 16 DF, p-value: 0.003113 This isn't exactly a very good fit, even if all the coefficients and the model itself are significant. So far, my brewing hasn't shown mash temperature to be important in predicting attenuation. Have fun! Chris - -- Christopher S. Swingley email: cswingle at iarc.uaf.edu (work) Intl. Arctic Research Center cswingle at gmail.com (personal) University of Alaska Fairbanks www.frontier.iarc.uaf.edu/~cswingle/ Return to table of contents
Date: Tue, 12 Oct 2004 20:36:49 -0500 From: "Rob Moline" <jethrogump at mchsi.com> Subject: FOY, 2004 -Response- Published attenuation levels for various yeasts- Fred Johnson FOY, 2004 -Response- Published attenuation levels for various yeasts- Fred Johnson Commercial yeast producers and others publish attenuation figures for each yeast. Are these figures obtained using a standard protocol within the company publishing the results? Are these figures obtained using a standard protocol across the industry? If so, how does that protocol relate to the vast array of wort compositions and fermentation conditions that are encountered in the commercial brewery and in the home brewery? I suspect that the reasons yeasts vary in the degree to which they attenuate wort are only partly known, but I would appreciate a brief summary of what is known about this. Fred L Johnson Fred, There is no standard procedure to determine the attenuation properties of yeast strains. Usually yeast producers have internal standard wort and conditions to compare the different yeast strains. But you are absolutely right that wort composition and fermentation conditions vary from brewery to brewery, which has a huge impact on attenuation. That is why we do not give definite attenuation values for each yeast strain but put each yeast strain in an attenuation group (High, medium, low) based on fermentation results with our standard wort and fermentation conditions. This way the customer is still able to select a yeast strain that suits best his beer style but they have to determine the absolute attenuation under their specific conditions for themselves. The attenuation properties of a yeast strain depend on various factors. Flocculation properties of a strain can influence attenuation; a very flocculent strain that settles before the fermentation is complete will leave more residual sugars in the beer than a strain that stays in suspension longer. Lager yeast usually attenuates relatively high whereas ale yeasts show larger differences in attenuation depending on their metabolism. One factor is the ability to use maltotriose. Regards Tobias & Forbes - --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.775 / Virus Database: 522 - Release Date: 10/8/2004 Return to table of contents
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