HOMEBREW Digest #4624 Sun 10 October 2004

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  Atteunation, yeast vs wort (was Re: Cider and "low attenuation" yeast) ("Fredrik")
  Re: Cider and "low attenuation" yeast ("-S")
  Re: low-attenuating yeast (Fred Johnson)
  Info needed on Brewpubs in New York State (marty)

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---------------------------------------------------------------------- Date: Sat, 9 Oct 2004 09:43:33 +0200 From: "Fredrik" <carlsbergerensis at hotmail.com> Subject: Atteunation, yeast vs wort (was Re: Cider and "low attenuation" yeast) Whoa, n'th post-attempt after cutting lines n-1 times, sending this to the wrong address etc! This is driving me nuts :o) Hope the short lines doesn't make this unreadable. > Date: Thu, 7 Oct 2004 07:26:57 -0400 > From: Fred Johnson <FLJohnson at portbridge.com> > Subject: Re: Cider and "low attenuation" yeast Fred Johnsson wrote that atteunation *mainly* (not only) depends on the wort, and that the attenuation ranges posted by the yeast manufacturers apply to some undefined standardworts, fermented using some standard pitching rates, and under otherwise standard conditions. I agree completeley with this. Since this came up I thought I could post some of my thoughts on this subject, showing some ballpark estiamtes I have been using until I've got a full model running. Certainly the exact attenuation depends on the full set of variables, ranging from yeast, wort and fermentor and ambient variables. But for practical purposes, in order to at least be able to do a little bit better ballpark estimates than the standard attenuation ranges posted on the yeast manufacturers page I have decomposed the problem into two parts. Assumptions used in this ballpark estimate 1. The most relevant ferementables in beer wort are glucose, fructose, sucrose, maltose and maltotriose. 2. Under at least "reasonable conditions, picthing rates" most strains(there might be some exceptions) fully deplete everything except maltotriose. Definitions. I have attempted to parametrise the wort sugars by ... RDFW = Real Degree of Fermentabilit of Wort (=glucose+ fructose+sucrose+maltose; % of extract) MTW = MaltoTriose contents of Wort (% of extract) RDF = Real Defree of Fermentability (in actual fermentation) MTD = MaltoTrioseDepletion (% of maltotriose depleted) This in this simplified variable set one would arrive at this relation RDF = RDFW - (1-MTD)*MTW Thus the upper limit of fermentability is totally determined by the wort (RDFW). There is no hard lower limit but for "most strains" and for "reasonable" conditions I would assume that the lower limit is approximately RDFW - MTW. What remains is to estimate MTD and MTW. If you are using DME hopefully there are datasheets. I think muntons light DME has something like MTW = 10.4% (could be a little lower maybe) RDFW = 65% I am still working on getting control over my mashing. But eventuelly I belive that MTW as well a RDFW could be at least roughly estimated from the mash scheduele, by means of modelling the mash. I started this project but has had time to work on it as much as I'd hoped. But evenetully I figure it will fall into place. I think the hard parts is not enzyme modelling, the hardest parts seems to be modelling the liquification of grains and starch, but I am still working on it. Until then I rely on basic empricial formulas. Fix suggests some simple relations between MTW and RDFW if you are using a fixed scheduele. Otherwise I figure you can do some attenuation testing using low and high strains to pinpoint roughly the wort parameters. I have transformed this into another rough formula directly involving FG. There may be some minor errors in thte constants from the fitting, since it depends on alot of things. FG = (a*OG + b) ( RDFW - MTW*(1-MTD)) + (c*OG +d) a = -1,180875689 b = 1,179398127 c = 0,993948859 d = 0,006096669 To estimate the MTD. I have made an assumption of this "standar wort" they must be using, And translated their apparent attenuation ranges into MTD ranges. It's admittedly a bit foggy, but I figured it's the best you can do at the moment and better than nothing. Until there is a better model. I emailed wyest on this standard wort issue, but they didn't respond. My wild assumption is that the standard is something like 1.040-1.045, RDFW=64-65%, MTW = 10.5%, pitching rate = 1 million/ml/P and otherwise normal fermentation. Eventually I hopeto be able to find a better estimate for MTD that also includes some starvation and ethanol inhibiation issues and pitching rate. For example if you fermented cider I assume MTW would be practically 0% and all strains should have pretty similar and full attenuation, unless it runs out of some other nutritons. That is the next step to find out. I am still tuning the fermentation model. Right now I am trying to invent some conditions to regulate transition from active to dormancy. I am working on energy stress model, where I translate all stress factors into energy equivalents, and the idea is that at the point where the stress factors are more costly than the energy production do to hard digestible or low concentration of sugars, the cells will go dormant. So I think of stress as a king of energy thief/leakage. The the accumulated weigthed stress is what I will try to trig on. So far I think the idea looks promising. One objection to this is that estimates MTD and MTW aren't easy. But I think it can be done good enough, to allow far better FG estimates that the figures put on the yeast companies webpage that seem based on undefined standards. I have only brewed for 1.5 years so I do not have alot of experience, but so far I have found my estimates using this accurate enough, within the measurement errors. I have made some receips from scratch, and the only times I have had major deviations from my estimates is when have done AG. The problems is that I yet do not have a reproducable procedure that I can model. /Fredrik Return to table of contents
Date: Sun, 10 Oct 2004 00:32:36 -0400 From: "-S" <-s at adelphia.net> Subject: Re: Cider and "low attenuation" yeast On low attenuating yeast, Fred Johnson wrote .... >Certainly >this is a reasonable question considering that the yeast companies >describe their yeasts in terms of their level of attenuation, and one >would assume that the figures for attenuation for the yeast are tell >you what the yeast will do. Such was also my assumption until I >repeated discovered that the figures often don't really apply. [...] I agree with Fred's comments. Not only do brewing yeast companies but also yeast banks like NCYC characterize yeasts on the degree and rate of attenuation, *BUT* those figures only have meaning when the media(wort), the yeast handling and the growth conditions are standardized. Common brewing results could be entirely different. One thing that is very puzzling wrt attenuation is that different yeasts do 'give up' sooner than others, yet we can say with confidence that all brewing yeasts ferment all major fermentable wort sugars - Maltose, Glucose, maltotriose and residual sucrose, to some extent. Let's put some numbers to this. Some typical 12P(1.048) wort may achieve a 75% attenuation under forced fermentation conditions. 75% attenuation requires the conversion of about 61% of the extract into ethanol or fermentation of 7.3 Plato of sugar. [Yes, only ~60% of extract is fermentable in a typical wort !] In similar worts the mass breakdown of fermentables is roughly: 62% maltose 19% maltotriose 13.5% glucose 5.5% sucrose (actually 90% sucrose w/ minor amounts of others) As the wort attenuates and gravity readings drop from 1.048 to 1.012, the 36 gravity degree change is nearly proportional to the fermentable sugar mass converted to ethanol. So of the 36 degrees lost, about 62% of that is attributable to maltose fermentation and so on. This gives the attenuation contribution as: 22.3 grav.degree, maltose 6.8 grav.degree, maltotriose 4.9 grav.degree, glucose 2.0 grav.degree, sucrose et al We know from studies that most (certainly not all) healthy brewing yeasts will completely ferment out glucose, sucrose, maltose in wort and that the amount of maltotriose unfermented is among the more variable portion of what is fermented. This means that 29.2 degrees of attenuation(81% of expected attenuation) is 'given' in any reasonable fermentation of this wort. We fully expect that the 1.048 wort must drop to 1.018.8 for nearly any reasonable yeast. The question is how much of the remaining 6.8 degrees of maltotriose attenuation materialize. Looking down Wyeast's lists of apparent attenuation ranges expected from various yeasts we see values given a += 2 or 3% attenuation range. Considering the center point of this range and ignoring the high and low extreme yeasts we find that typical results for low attenuating yeasts give around 69% attenuation and high attenuating ones about 75% under Wyeasts conditions. This means a low attenuating yeast must typically consume 92% of the extract as a high attenuating ones. The 8% delta corresponds to low attenuatnig yeast capable of fermenting all the maltose, glucose, sucrose and about HALF of the maltotriose in quantity. A few rare yeasts may turn up their noses at sucrose or fail to finish the maltose or whatever but it's a fair generality to say that the difference between high and low attenuating yeasts is how they handle the LAST HALF of the maltotriose. Here's the puzzle - why do low attenuating yeast stop fermenting when there is still plenty of food on the table ? Obviously these yeasts have the metabolic mechanisms to consume maltotriose - so why not finish the meal ? More questions than answers this time, -Steve Return to table of contents
Date: Sun, 10 Oct 2004 06:10:11 -0400 From: Fred Johnson <FLJohnson at portbridge.com> Subject: Re: low-attenuating yeast Many thanks to Steve Alexander for his thoughts and comments on differences between low- and high-attenuating yeasts. After careful consideration of the various sugars and their proportions in wort, Steve poses the reasonable question (paraphrasing), "So why do these different yeasts leave behind different amounts of maltotriose?" This makes me wonder, "Are all maltotrioses the same? And is there room here for some subclassification of these sugars, in which case a particular yeast can transport and metabolize certain maltotrioses but not other maltotrioses? Or perhaps there is a difference between yeasts in the kinetics in the uptake or metabolism of maltotriose (and for other sugars also), such that the transporter(s) on some yeast strains simply do not transport appreciably when the concentrations of the substrate gets below a certain level. Perhaps we should pose this and related questions to the yeast experts in the Fortnight of Yeast, 2004. I'll start this ball rolling and post a question to Drs. Fischborn and Waldrop tomorrow. Fred L Johnson Apex, North Carolina, USA Return to table of contents
Date: Sun, 10 Oct 2004 14:04:10 -0400 From: marty <bigbrewdude at optonline.net> Subject: Info needed on Brewpubs in New York State Hello all, I'm new to the HBD, so I don't know if this has been discussed already... One of my buddies is buying a pub and he asked be to get all the information I could about what hoops the government want brewpub owners to jump through. Any ideas who to contact? Any help would be appreciated. Return to table of contents
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