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HOMEBREW Digest #4955
HOMEBREW Digest #4955 Sun 19 February 2006
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
Digest Janitor: pbabcock at hbd.org
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Contents:
diacetyl anyone ? ("steve.alexander")
AHA National Homebrew Competition Comes To Philadelphia ("David Houseman")
compost (Glyn Crossno)
Hogmanay Het Pint? (Alexandre Enkerli)
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Date: Sat, 18 Feb 2006 08:36:11 -0500
From: "steve.alexander" <steve-alexander at adelphia.net>
Subject: diacetyl anyone ?
Chad Stevens & /Fredrik discuss the VDK vs ferment temp issue
which I have doubts about. Here's an outline for the viewers at home:
Yeast need to make the amino acid valine and to do so they divert some
pyruvate first converting it to alpha-acetolactate(AAL). A considerable
amount of AAL escapes into the wort.
The AAL in the wort is converted to diacetyl by a non-enzymatic process.
This conversion rate is very dependent on pH, going faster at lower pH.
Yeast have a very strong capability to take diacetyl and convert it to
acetoin
and then perhaps to 2,3,butanediol. This is a good thing for brewers since
these latter two have little impact on flavor compared to the very
potent diacetyl.
Throughout fermentation the levels of wort AAL is much higher than diacetyl
level. (3X or 4X higher). Note that to have a flavor stable beer we
have to
remove enough of the diacetyl AND the AAL so that objectionble levels of
diacetyl do not appear in the bottle or keg after yeast separation.
Chad says ...
>I'm not sure why. Anecdotally, I know that the only ferments in which I
>experience residual diacetyl, are those which were conducted entirely in
>cold environs.
That makes sense to me. Cold fermentation causes less FAN uptake
so I'd expect a marginal decline in AAL release into wort (<20% I'd expect).
But cold fermentation also causes wort to acidify less and more slowly so
the AAL -> diacetyl conversion rate is down significantly. Also yeast
remove diacetyl much more slowly with lower temp. In all I'd expect low
temps to increase the AAL and diacetyl pools. Even if you get the diacetyl
level low before yeast separation you may still have enough AAL hanging
around to make too much diacetyl in the bottle.
Actually Chad's anecdote matches diacetyl curves in Kunze where it
takes much longer to resolve diacetyl after a cold-only ferment & lager.
>I think the non-enzymatic decarboxylation reaction is dependent upon heat;
>the greater the temp, the more rapid the reaction.
Right, certainly but that doesn't help. All that means is that there is
less
diacetyl for the yeast to convert to acetoin and more remains as AAT
which later converts to diacetyl in the bottle.
If we had some special sauce we could add to the fermenter which
would instantly convert all the AAL to diacetyl we would definitely use
it. Not because we want more diacetyl, but because we want the yeast to
deal with all diacetyl *and* the precursor AAL before yeast separation.
Yeast can only deal w/ diacetyl so we want as much AAT converted in
the fermenter as possible. Cold is the enemy in this respect. Actually
such a special sauce is available in the form of bacterial AAL decarboxylase
enzyme and sold as a brewing aid. There is also work underway to
introduce this gene for this enzyme into the yeast genome for brewing.
Hmmm GMO beer !
>But there again, everything in yeast metabolism occurs at
>a more rapid rate at warmer temps. So I think there may be some face validity
>to the notion that allowing the ferment to free rise to a warmer temp will
>result in a quicker 'driving off' of diacetyl.
>
>
Right but it's not the rate, but the total product what we care about.
That is the total
AAL produced minus the amount of diacetyl removed. Cold ferment causes
a bit less
mass growth and less FAN use. Perhaps it's because the protein turnover
is lower at
lower temps. So we'd expect the total AAL spill to be a bit less but
also the diacetyl
removal to be less or at least much slower.
/Fredrik writes ...
>The way I
>understand that part, the diacetyl production is related
>to the amino acid uptake sequence and the
>amino acid balance vs de novo synthesis pathways. And
>as long as high preference (group A) amino sources are available
>the inhouse biosynthesis of valine and leucine
>stimulate acetolactate production.
>
>
I see that high levels of valine & isoleucine (class B aminos) also prevents
AAL production (and alpha-acetohydroxbutarate/2,3pentanedione for
isoleucine).
>But set aside other more complex possibilities, they way
>this is currently encoded in my head the
>non-enzymatic oxidation of alpha-acetolactate
>to diacetyl outside the cell is favoured by a higher temperature.
>And this step seems to be the bottleneck
>(which is probably why diacetyl sometimes tend to
>appear again out of nowhere in keg or bottle), so the sooner
>all the "potential diacetyl" (alpha-acetolactate) is converted to
>free diacetyl, the sooner can it be reassimilated and reduced
>by yeast to acetoin and butandiol.
>
>
This makes sense and argues that a warmer ferment (or at least a VDK rest)
favors the VDK removal.
Yeah something is amiss here. Perhaps the cold really radically
reduces AAL
production for reasons not explained here. As Fredrik says it is a complex
issue with many competing effects adding to the whole. It just looks
wrong to
me.
-S
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Date: Sat, 18 Feb 2006 21:16:27 -0500
From: "David Houseman" <david.houseman at verizon.net>
Subject: AHA National Homebrew Competition Comes To Philadelphia
Judges, are you ready to judge the 1st Round of the 2006 AHA National
Homebrew Competition in Philadelphia? Yes, this year, the Eastern Regional
will be held in Philadelphia, at the HRIM Academic Bistro of Drexel
University on Friday night and Saturday, April 28th and 29th. All BJCP
judges are welcome.
Friday judging, for those that are local or wish to come in the night
before, will commence at 7:00pm. Pizza and beer will be available from 6:15
until 7:00.
Saturday judging will commence at 9:00am and proceed with up to three
sessions of judging. Lunch will be served as well as a beer and hors
d'oeuvre reception just after judging. The Reception will also be a BYO
affair, so feel free to bring your own homebrew to share but we'll have
plenty of other beer there as well. For those that can stay around, there
will be a hosted pub crawl by the knowledgeable George Hummel from Home
Sweet Homebrew and Mid-Atlantic Brewing News.
The Drexel University Academic Bistro is within a few minutes walk of
Philadelphia's 30th Street Station, the main hub for local commuter trains,
subways and Amtrak's Northeast Corridor trains from Boston to Washington.
Upon exiting the 30th Street Station, proceed West on Market Street to 33rd
Street. Turn Right and go to the Academic Building on the Northeast Corner
of 33rd & Arch Streets. The Academic Bistro is on the Sixth floor. There
is parking available on the street (watch time turnover and meters). Free
on-street parking is available on 32nd Street, North of Powelton. Google or
Yahoo! MAPS for driving directions to this location.
So plan to visit Philadelphia, judge some beer, drink more beer and have a
great time with old friends. For those of you from out of town, the Best
Western Center City at 22nd & Pennsylvania, next to the Parkway and the
museums, is the cheapest. Otherwise there are hotels around the University
of Pennsylvania and Drexel Campuses. Center City is also nearby. This
could make the weekend a family affair. This weekend will also see
Philadelphia host the Penn Relays, so if you want a hotel reservation, get
those in very soon. Parking will also be at a premium, so do consider
public transportation as your best option.
Contact David Houseman, judge coordinator, at david.houseman at verizon.net to
reserve your judging assignment. Let him know what categories you cannot
judge, prefer to judge and prefer not to judge. Let him know whether you
can judge Friday, Saturday or both. Contact Nancy or George at Home Sweet
Homebrew (www.homesweethomebrew.com) if you have other questions or need
help with hotels.
Of course, go to the AHA website for information on entering the AHA
National Homebrew Competition as well.
------------------------------
Date: Sun, 19 Feb 2006 05:36:51 -0800 (PST)
From: Glyn Crossno <graininfuser at yahoo.com>
Subject: compost
How do you get 31 lbs of grain dry enough to compost?
To keep the critters out I compost in a barrel that I
roll around 7 or 8 times a day. But with that much wet
grains it almost always stinks a little bit.
Does the barrel need more hole? Turn it 7 or 8 times
twice a day? Is there something I could add to the
compost to suck up some of the moisture?
Bottle gushers:
If relatively new brewer, I would blame an infection.
After 2 years of brewing I noticed the last few
bottles in the batch were "over carbonated". After
trying a few things I finally figured out in my case,
take the spigot off the bottling bucket and sanitize
first. Then put back on and do the bucket. Since then
(12 years) I have had only one batch that I could not
check the FG on (broken hydro) and had to relieve the
pressure on by cracking the lids.
Glyn
1 hour from Huntsville, AL
1 hour from Nashville, TN
1 hour from Chattanooga, TN
------------------------------
Date: Sun, 19 Feb 2006 17:14:05 -0500
From: Alexandre Enkerli <enkerli at gmail.com>
Subject: Hogmanay Het Pint?
Hmmm...
Was listening to the EatFeed.com podcast and they mentioned an ale drink
served at First Footing for Hogmanay. It was called a "het pint" and was
a mixed drink of ale, nutmeg, and whisky. (Online recipes seem to
include eggs too.) Now, we're way passed the
Kwanza/Hanukkah/Hogmanay/Christmas Holiday Season, and it's a beer drink
instead of a beer style, but did any here experiment with something
similar to this?
Couldn't find anything in the archives about it.
Cheers!
Alexandre (aka Ale-X), in Montreal
[555.1km, 62.8] Apparent Rennerian
http://enkerli.wordpress.com/
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End of HOMEBREW Digest #4955, 02/19/06
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