HOMEBREW Digest #4848 Thu 15 September 2005

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  Re: esters, acids, and practical ideas for fermenting beer ("-S")
  Binchoise ("Dave Burley")
  Binchoise Blonde ("Dave Burley")
  hops (yawn..) and sleepiness (snore) (bob.devine)

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---------------------------------------------------------------------- Date: Thu, 15 Sep 2005 04:14:56 -0400 From: "-S" <-s at adelphia.net> Subject: Re: esters, acids, and practical ideas for fermenting beer Matt says, > Anyway, I understand very well that in cases where some growth factor > other than sugar causes yeast growth to slow, we get a big spike in > ester production. I am tempted to call this a "stuck ferment ester > spike," and then ignore it because even when I want lots of esters I > plan to avoid sticking my ferments. It's not just a stuck fermentation spike. The yeast cells in our fermenters are in various states as fermentation comes to a close. Normally a "race" as to whether oxygen product, amino-acids or sugars will be the critical limit to growth. Many "normal" fements slow or even dawdle near the finish line yet attenuate well enough. Here part of the yeast population lacks growth conditions ! Perhaps sufficient O2 product (sterols and UFAs) are missing. Perhaps the amino synthesis capability of part of the yeast population is inadequate to induce maltotriose. Certainly some cells have less capable membranes than others and will halt earlier for energetic reasons. A stuck fermentation occurs when essentially all cells are growth inhibited (and produces a clear spike of esters). That's an abnormal case. In a dwindling fermentation some part of the yeast population has growth limitation and this fraction will produce the excess esters we are talking about. If your fermentation finishes powerfully and you only observe flocculation very near final attenuation, then you've probably minimized these "growth cessation" esters. BTW yeast only flocculate after they have ceased to grow, so the extent of flocculation is a very good indication of the growth-cessation condition. > BUT... maybe I'm going too far, > because maybe an ester spike happens even in healthy, sugar-limited > ferments as well. I suspect so, though probably smaller in magnitude as the acetylCoA supply dwindles. > This was really why I > asked whether there are still pools of Acetyl-CoA available after > growth stops--but I forgot to specify that I am most interested in the > case where growth stops *because the sugar runs out*. Any thoughts on > that? The three primary sources of acetylCoA in brewery yeast are the sugar catabolism path, the amino catabolism path and the fat beta-oxidation path. You have stated the sugar is gone, and normal beer has low amino levels. Beta-oxidation: yeast have the capacity for beta-oxidation, but it probably only occurs in essentially "starvation conditions". There are very few practical brewing studies on beta-oxidation in yeast. My hunch is that yeast in the bottom of your fementer, even a week after attenuation, are living in a low energy dormant state and fermenting the low concentrations of fermentables left, not burning fat. They are producing minimal levels of acetaldehyde which is primarily being converted to ethanol. In a previous post I mentioned that AAT is probably not available equally throughout fermentation, but may spike as growth ceases. I also would suspect that it's level falls off rapidly as cells flocculate. I wouldn't expect the flocculated yeast cake to become significant ester producers > An > acetaldehyde molecule has one less oxygen than an acetic acid molecule. > Where does the oxygen come from to make this reaction happen? Most texts just point to the pyruvate and the pyruvate dehydrogenase which together with a CoASH directly produce acetylCoA (actually it's a 3 enzyme, 3 step process). We know that doesn't happen in anaerobic yeast based on recent studies, the enzyme is absent. It appears that all the acetylCoA comes from pyruate -> acetaldehyde -> acetate (the acetic acid anion) -> acetylCoA, but most books supply few details. The first step is the same as the direct mechanism, applying pyruvate decarboxylase(EC4.1.1.1) in removing the carboxyl group of pyruvate which yields acetaldehyde. The next step applies an aldehyde dehydrogenase to the acetaldehyde. There are "aceylating aldehyde dehydrogenase" enzymes (EC1.2.1.10) which can produce acetylCoA directly from CoASH and aetaldehyde, but these don't occur in yeast. Instead yeast apply an EC1.2.1.3(or EC1.2.1.4, EC1.2.1.5) aldehyde dehydrogenase enzyme to the acetaldehyde and produce the acetic ion plus a little energy. The difference in these three classes of enzymes are whether the energy collection is via NAD+, NAD(P)+ or NADP+ - I don't know or greatly care which. Here is the reactions: acetaldehyde + NAD+ + H2O = acetic acid + NADH + H+ *** Note that the oxygen comes from water.*** Note also that this is different that the aerobic oxidation by acetic acid bacteria aerobic yeast which use free O2. > A Practical Idea: > Let's say, first of all, that we pitch an adequate amount of healthy > yeast into a sufficiently nutritious/aerated wort, so that the yeast > are still happy and healthy when the sugar runs out. Let's also say > that we want to minimize diacetyl and fusel levels. Finally let's say > that we can easily raise the ferment temp to at least the low 70s > whenever we want, just by leaving our carboy at room temperature and > letting the yeast do its thing. How do we use the ferment temp to > control esters? All of the causative factors (except he enzymes) interact, so you can't purely increase esters and also minimize fusels for example. It makes little sense to warm the ferment early when there is little alcohol, maybe little AAT, and plenty of growth to little free aceetylCoA, so warm the fermenter as the fementation declines. Also fermentation releases considerable heat and so insulating a fermenter will increase the temp connsiderably above ambient. Unfortunately the fusels are likely to be produced at the end as the amino acids dwindle. The warm active finish should pose no diacetyl problem I think a simpler approach to increasing esters is to reduce the pitching rate and oxygenation so the fermentation slows at the finish. Also modestly elevating the late fermentation final temps. >... FWIW Kunze discusses weizen beers which are highly estery ales and top sellers in Southern Germany. For these he starts with 11-12P wort, he pitches 0.3L to 1L of [slurry] per 100L {low to high pitching rate}, at 12C(54F) and allows the fermentation temp to rise to 13C-21C(56F-70F) over the 4 day fermentation. So yes he pitches cool and allows the temp to rise, perhaps considerably. > Ringwood yeast seems like another possible application. You'll never control the diactyl with that yeast !!! -S Return to table of contents
Date: Thu, 15 Sep 2005 10:01:01 -0400 From: "Dave Burley" <Dave_Burley at charter.net> Subject: Binchoise Brewsters, Chad Stevens asks about the flavor components in Binchoise' Brew. BINCHOISE BRUNE from Brasserie Binchoise is a complex artisanal Wallonian brown ale. It is flavored with aromatic hops, star anise and orange peel. It has dark brown color with reddish highlights, hoppy bite and aromatic spice character; rich and warming. Keep on Brewin' Dave Burley Return to table of contents
Date: Thu, 15 Sep 2005 10:30:48 -0400 From: "Dave Burley" <Dave_Burley at charter.net> Subject: Binchoise Blonde Brewsters: Here is some more info on Binchoise brews Chad asked about: BINCHOISE BLONDE from Brasserie Binchoise is a complex artisanal Wallonian blond ale. It is flavored with aromatic hops, coriander and a touch of Curacao. Has honey in the bouquet and peppery, dry, very appetizing finish. It has 6.5% alcohol ABV Binchoise Brune has an ABV of 8.2% Keep on Brewin' Dave Burley Return to table of contents
Date: Thu, 15 Sep 2005 17:25:38 +0000 From: bob.devine at att.net Subject: hops (yawn..) and sleepiness (snore) Jeff asked about some semi-rigorous connection between hops and sleepiness. Here are some that *sound* authoritative http://www.hort.purdue.edu/newcrop/duke_energy/Humulus_lupulus.html http://herbalgram.org/bodywise/expandedcommissione/he047.asp http://www.hbcprotocols.com/sleep/hops.html http://hops.sleeplibrary.org/ Many articles repeat the hops == soporific without providing a source. But here is a good source: http://www.uic.edu/pharmacy/research/diet/content/ scont_womens_health_hops_hlrefs.htm [Article in German] Abstract: Hops are told to promote sleep; manyfold efforts to detect the soporific principle have been unsuccessful so far. Preliminary pharmacological tests lead to the conclusion that the soporific activity of the exhalation of hops [essential oil] can be explained by its content of 2-methyl-3-butene-2-ol (1) in the volatile fraction. It was found that (1), when given to mices i.p. (800mg/kg) produces narcosis for about 8 h.; no abnormail behaviour was observed there upon. Due to its water-solubility the concentration of (1) in the essential oil obtained by steam distillation is low; contrary to that, (1), is enriched in the more volatile fraction of hops. Yeah, "mices" and "abnormail". This might be the referenced study http://www.ncbi.nlm.nih.gov/entrez/query.fcgi? cmd=Retrieve&db=PubMed&list_uids=9757514&dopt=Citation But the above study used a combination of hops + valerian. They conclude: "This study shows that the investigated hop-valerian preparation in the appropriate dose is a sensible alternative to benzodiazepine for the treatment of nonchronic and non-psychiatric sleep disorders." Bob Devine Riverton, Utah Return to table of contents
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