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HOMEBREW Digest #2707
HOMEBREW Digest #2707 Thu 07 May 1998
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
Digest Janitor: janitor@hbd.org
Many thanks to the Observer & Eccentric Newspapers of
Livonia, Michigan for sponsoring the Homebrew Digest.
URL: http://www.oeonline.com
Contents:
1.035 IPA's, Boil Roll and Evaporation Rate (Tony Barnsley)
I did a pretty silly thing... ("Kris Jacobs")
Re: Starters ("Timothy Green")
Stout/Porter (Mark Garthwaite)
Hop spacing (Matthew Arnold)
RE:Boil Roll and Evaporation Rate (Charles Burns)
Delta-T and External RIMS Heat Sources (KennyEddy)
SS conical fermentors ("Frank E. Kalcic")
Big 10/20 ("Philip J Wilcox")
Alcohol/Aldehyde or Redox Redux I ("A. J. deLange")
Alcohol/Aldehyde or Redox Redux II ("A. J. deLange")
Boil Roll and Evaporation Rate (Troy Hager)
chocolate Porter (good head) ("Taber, Bruce")
kettle evap rates (dbgrowler)
RE: Confusion over delta T (LaBorde, Ronald)
AHA Nationals ("Capt. Marc Battreall")
BURP's Spirit of Free Beer competition is June 6-7 and entry information
is available by contacting Jay Adams (adams@burp.org).
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----------------------------------------------------------------------
Date: Wed, 6 May 1998 09:37:54 +0100
From: Tony Barnsley <Tony.Barnsley@riva-group.com>
Subject: 1.035 IPA's, Boil Roll and Evaporation Rate
Al K Wrote
>when British brewers create 1.035 beers and call them
>"IPAs" then the brewer needs a little perspective adjustment.
Way to go Al! I'm right with you on this one. I get fed up of the mega
breweries over here brewing piss water and trying to pass it off as
something else. I used to work for a large independent that got taken
over by S&N (As Was), we had a couple of really good pilsner type lagers
that consistently won prizes at the GBBF. The new MD was given the task
to kill demand for these lagers and push McUrines, which was done very
successfully. It's somewhat sad to note that the Matthew Brown name is
now being killed having been associated with brewing for 150 years. S&N
were only interested in the Theakstons products anyway.
Troy Hager Wrote
>3. Cover the kettle partially to allow a more rolling boil and to lower
the
>evaporation rate to 10%. BTW, isn't this essetially what the pros do?
Their
>kettles are partially covered with a vent tube to carry off the
>evaporations, aren't they? To simmulate this design, how about
something
>like a wok top with a hole cut in it to allow a limited evaporation? I
have
>heard so much about "NEVER cover the boil!" I personally don't see
>anything wrong if you partially cover your boil and hit about 10%
>evaporation rates. This would be enough to drive off the DMS - correct?
I have an electric 10 Gallon boil kettle with two 3KW heaters in the
bottom.
Now A 1KW Heater will evaporate about 1.6 Litres per hour so I figure
that a 3KW will get rid off 4.5 litres or 1 UK Gallon, about 10%! so far
so good, however its 20% when I brew a 5 gallon batch (plus I boil for
90 minutes anyway). One of the heaters is fitted with a simmerstat (TM)
so I can turn it down but then lose the rolling boil. So my solution was
to fit the lid and lift the front so that some steam and DMS can escape.
This causes boil overs however when the full 6KW are going to get to the
initial boil.
Another solution would be to add boiling water to the kettle to keep the
wort level at the desired level. i.e. 5.5 Gallon initial vol. then add
boiling water when the level drops below 5 Gallons.
Wassail!
Tony, M.I.B (Mashing In Blackpool, Lancashire, UK)
------------------------------
Date: Wed, 6 May 1998 08:36:42 +0000
From: "Kris Jacobs" <jtsnake@mail.net-link.net>
Subject: I did a pretty silly thing...
Last weekend I kegged up two batches of beer. I had never dry hopped
before, so I figured I would try it. I have read multitudes about
it, so I know better than what I did... perhaps I had consumed one
too many hydrometer samples.... Hehe
I dropped two EKG plugs into each keg. Now, of course, I
get hop particles out my tap into my glass. I don't really care to
drink it like this, and have been wondering how to remedy the
situation. Here's a possibility: I have a third clean keg empty, and
a hose with just a flare fitting on one end, and some muslin grain
bags left over from when I steeped grains in extract. Purge the
empty keg, fill it with CO2. Tie on a muslin bag over the open end
of the hose. Attach the hose to the liquid out of the affected beer.
Put the end of the hose with the "filter" on it into the bottom the
empty keg. Push the beer from one keg into the other, hoping to
catch all the loose hops in the "filter". Repeat for second batch.
Does this seem like a viable solution? Is there an easier way? Am I
overlooking something?
TIA,
Kris Jacobs
Galesburg, MI
------------------------------
Date: Wed, 6 May 1998 09:36:31 -0400
From: "Timothy Green" <TimGreen@ix.netcom.com>
Subject: Re: Starters
Michael Lausin writes:
>it now appears that the initial ferment is over, time to add the champagne
>yeast. how do i do a starter for the champagne yeast or is it better to
>just pitch a pack into each carboy?
I have been using champagne yeast for a number of years for my mead making
efforts. The easiest way I know to make a starter is to mix 1 pt of boiling
water with 1/4 cup honey, 1/4 DME,3 tbsp sugar and 1/2 tsp yeast nutrent.
Put this liquid in a 1/2 gallon jar, seal it and shake until all is
dissolved. Cool to pitching temp and pitch the yeast and shake well.
I take a paper towel folded in quarters and rubberband it to the top of the
bottle. I tried a drilled cork of the proper size with an airlock, but the
yeast takes off so fast, it blew the airlock right off. If your paper towel
filter becomes fouled, you can just replace it with another.
You should be able to build a reasonable starter in about 24-36 hours.
Tim Green
------------------------------
Date: Wed, 6 May 1998 09:07:26 -0500 (CDT)
From: Mark Garthwaite <mgarth@primate.wisc.edu>
Subject: Stout/Porter
I agree with Spencer re: stout preceeding porter. I seem to
remember reading that the term "porter" was derrived from the person who
served the ale to the patron. Perhaps the thirsty customer would call
out to what we call a waiter/waitress and order " A stout, porter.",
similar to how I might order " A beer, waiter." Maybe the two words became
connected as such. Don't know how they would have separated though.
------------------------------
Date: Wed, 06 May 1998 14:28:50 GMT
From: marnold@netnet.net (Matthew Arnold)
Subject: Hop spacing
I'm about to plant some hop rhizomes and have been trying to read up on as much
as I can. The things I've read say that the same variety should be planted at
least three feet apart, dissimilar varieties five feet. Is this because of the
root systems or is it more of a practical consideration, perhaps to keep the
bines from two different types from growing together and intertwining? Will it
really matter if I plant one type four feet away from another?
Any thoughts?
Matt
- -----
Webmaster, Green Bay Rackers Homebrewers' Club
http://www.rackers.org info@rackers.org
------------------------------
Date: Wed, 6 May 98 08:06 PDT
From: cburns@egusd.k12.ca.us (Charles Burns)
Subject: RE:Boil Roll and Evaporation Rate
Troy Hager <thager@bsd.k12.ca.us> makes an excellent post in HBD#2706:
<snip> In all of the literature I have read, the recommended
rate of evaporation is 10% of your starting volume
<snip>
They (Fix) state
as guidelines that "The best general recommendation is an evaporation rate
of 9-11%. In all cases, avoid evaporation rates in excess of 15%" and that
"also striking is the number of times the negative effects from (excess
evaporation) are incorrectly identified as problems in fermentation."
[charley] I'd like to hear more discussion on this. What's the big deal
about evaporation? Why would that affect the beer negatively? It increases
concentration (OG) but other than that what is the real effect on the wort?
[troy]Well, with my setup, a moderately rolling boil will evaporate about 1 gal
per hour. I brew 5 gal batches and usually start with about 7 gal in the
kettle and at the end of the 90 min boil I am left with 5.5 gal. 1.5/7 =
21.4% evaporation rate - way over the recommended 10%
[charley] this too is my experience. I use the 8.3 gallon pot and lose 20%
every time. Sometimes I sparge a little extra and add the final runnings in
later in the boil to keep up the volume. I have always been somewhat suspect
of this procedure and feel it may be more detrimental to the beer than
overboiling. What is the concensus on this?
<snip>
[troy]3. Cover the kettle partially to allow a more rolling boil and to
lower the
evaporation rate to 10%. BTW, isn't this essetially what the pros do? Their
kettles are partially covered with a vent tube to carry off the
evaporations, aren't they? To simmulate this design, how about something
like a wok top with a hole cut in it to allow a limited evaporation? I have
heard so much about "NEVER cover the boil!" I personally don't see
anything wrong if you partially cover your boil and hit about 10%
evaporation rates. This would be enough to drive off the DMS - correct?
[charley] what a great idea (wok top). What says the experts on this forum
about this?
Charley
------------------------------
Date: Wed, 6 May 1998 11:29:29 EDT
From: KennyEddy <KennyEddy@aol.com>
Subject: Delta-T and External RIMS Heat Sources
Matt Harper considers using an external RIMS heater chamber heat source and
asks for our experiences:
"I've been contemplating a non-standard heating chamber using an
external mounted (wrapped) heat source (tape or ceramic) that
gets wrapped around the pipe. However, some of these beasties
have pretty high temps. A good flow rate would help reduce the
(proposed) risk, but I dunno. Has anyone tried this method?"
While I have not (yet) test-driven this kind of equipment, I have looked
pretty closely at it and in fact have a boiler/mash-tun with a heater
installed, but which I have not gotten around to trying out just yet. Here's
what I *can* tell you.
What I've looked at are the silicone flexible heater "blankets" sold by a
number of suppliers, Omega (www.omega.com) and McMaster-Carr
(www.mcmaster.com) coming to mind (I bought mine from McMaster). These
heaters are made by sandwiching a metal foil or wire heater between two thin
layers of silicone rubber. They are usually available with and without a
pressure-sensitive adhesive to attach it (I got mine with).
They are available in different watt densities, meaning they generate a given
amount of power per square inch of area. Total power is then watt-density
times area; the bigger the heater, the more power. The models sold by Omega
and McMaster come in 2.5, 5, and 10 watt per square inch densities. Obviously
the watt density is the critical factor in pushing a certain amount of heat
through a certain fixed area such as the surface of a pipe.
Let's say you want to make a 1500W heater chamber using 1-1/2" diameter copper
pipe and a 10W/sq-in heater. the circumference of the pipe is just under 4",
so a 3" wide heater would be all you could use. You need 1500W and the heater
generates 10W/sq-in, therefore you need 150 square inches. Thus the heater
(and therefore the pipe) needs to be 50" long (just over 4 feet). By
extension of this reasoning, a 5W/sq-n unit would have to be 100" long while a
2.5W/sq-in unit would have to be 200" (almost 17 feet!!).
Some time ago, "Mr RIMS" Dion Hollenbeck indicated that his specified heater
cartridge generated 14 W/sq-in (if memory serves), without scorching or
overheating, so it would seem reasonable that a 10W/sq-in flexible heater
should do the trick. Problem is, the literature for the flexible heaters
indicates that the 10W/sq-in units can overheat beyond the melting point of
silicone, so that some external temeprature control is required. (Although
the implication is that the lower watt-density models do not pose this risk, I
would assume otherwise and follow all precautions).
Now, in a system where the heater is in close contact with the transfer
surface (pipe), with a constant turbulent flow of wort on the other side of
the surface (inside the pipe), it would seem that most of the heat should be
sucked into the wort and help limit the temperature rise. I intend to test
this soon, though my configuration is a disk-shaped heater stuck to the bottom
of an aluminum pot. I'll attach a thermocouple to the heater pad and add some
water to the pot, turn on the heater, and see whether the aluminum and water
will sink enough heat to prevent overheating. Chances are, it won't,
especially in the kettle application where the water isn't moving (so heat
transfer is not as efficient).
Another consideration is personal safety. Even if the heater is happily
dumping heat to the load as fast as it can make it and not overheating, the
heater will still reach temperatures which could badly burn you. I would wrap
the pipe with fiberglass or other insulation to protect yourself. This also
has the advantage of directing more heat into the wort instead of heating your
basement air. For the kettle application, I'll simply set the thing down on a
layer of fiberglass or welding pad.
Both the safety factor as well as the potential for overheating still need
consideration (what if you ran the unit without wort by mistake, or the pump
failed while you and Jack Schmidling were off watching a football game during
a RIMS mash?). I would strongly advise adding some sort of temperature-
sensing system regardless of the heater or configuration. A thermistor bridge
sensor could be used. High-temperature thermal snap-switches set to all sorts
of temperatures are available from electronics suppliers, or you could even
rip one out of an old hair dryer. Use this switch to control the coil of a
relay (solid-state preferably) which carries the main heater power. Be sure
the trip temperature is above your expected maximum temperature but below the
meltdown point of the heater (450F for silicone). Something like 250F to 300F
is probably about right.
Flexible heaters are available in different materials (Kapton being one) and
shapes (square, rectangular, round, tape) which may offer their own advantages
depending on the application. In any case, the giudelines I have offerred
here should still apply.
*****
Ken Schwartz
El Paso, TX
KennyEddy@aol.com
http://members.aol.com/kennyeddy
------------------------------
Date: Wed, 06 May 98 09:03:31 -0700
From: "Frank E. Kalcic" <fkalcic@flash.net>
Subject: SS conical fermentors
Jim- saw your posting on the HBD today. I went around in circles with the
same problem last December. Conicorn is out of business. Believe it or
not, not enough market demand and he wasn't making any money at it.
>From the photos, this looked like a real quality product. The Sabco
looks OK in its construction, but not as nice as Brewers Warehouse
(BITOA). The $1,400 to $1,800 price tag is a bit much for the average
guy. I know the prices listed for these SS conicals seem pricey, but
believe me pricing a custom job locally would run the same amount.
A few suggestions:
1) do you really need the conical feature? You will appreciate its
function if you are harvesting your yeast. Otherwise a racking arm
will do a better job of removing the clear beer from the trub.
2) A closed fermentor with an "IN" CO2 fitting combined with a
racking arm will allow you to transfer under pressure (allowing f
iltering if you wish) and preventing infections or oxidation through
exposure to air.
3) once you have a conical you now have to find a way to keep
the temp at the correct level during fermentation. It can be done,
but walk in coolers or glycol jackets and pumps are not inexpensive.
Better to stick with something that will fit in a fridge or chest freezer.
FYI I stayed away from the conicals available on the market and
opted to have SABCO modify their 1/2 Bbl keg fermentor as follows:
*1.5" TC flange welded to the side of the keg just below the lower
strengthening ring. (this is the racking arm port)
*get rid of the plumbing and fittings that run from the bottom of
the keg to the top & the temp gauge
*use one of the Cornelius fitting on the top for a pressure release
valve with a pressure gauge. The other CO2 fitting will be used
for a blow off tube during initial fermentation and then a CO2 in when
racking.
One can also carbonate naturally with this system if desired.
Just remove the blow off tube near the end of the ferment and
set the pressure release at the desired level.
The biggest drawback with a racking arm is that you will have
to invest in a TC valve ($135 - $150)and a few TC fittings. This
TC clamp allow fairy good seal while the arm is rotated to lower
the liquid inlet.
Lastly one can look at surplus dairy locations for misc. equipment,
but note the conical slope should be 60 Deg. Anything less and
you will have too much yeast and trub sticking to the cone.
Check out http://www.capecod.net/~mduffley/fpage2.htm for some
good photos on a racking arm and what I consider a really
nice/ functional fermentor.
Good Luck
Frank E. Kalcic
Sunnyvale, CA
<`)))>>< <`)))>><
<`)))>>< <`)))>>< <`)))>><
------------------------------
Date: Wed, 6 May 1998 14:01:18 -0400
From: "Philip J Wilcox"<pjwilcox@cmsenergy.com>
From: Philip J Wilcox@CMS on 05/06/98 02:01 PM
From: Philip J Wilcox on 05/06/98 11:57 AM
To: homebrew@hbd.org
cc:
Subject: Corn Stuck Mashes /Burners / Kettle Evaporation
Hi all,
David Bradley (whose email provider bounced my attempts all day
yesterday...) was bemoaning stuck mashes using boiled flaked maize....Faked
maize is already gelatinized in the flaking process. You do not need to do
a Cereal mash with it. By doing so my guess is that you created a lot of
beta-gluten gums that tended to set like concrete. The cereal mash would be
necessary if you were using grits, cornmeal, or rice.
Phil --
(Living 30 miles from Jeff Renner has its advantages....)
- ---------------
I am very happy with the 3 $14.75 (each) burners I have from Metal Fusion
of Louisiana. Of course you have to make you own stand...but for 2-tier 1/2
Barrel that's an inherent part of the system. I have found prices going
down on these things this spring compared to what I was shopping for just
last spring when I purchased a damaged off brand Cajun Cooker from a Home
Depot in Traverse City Mi. List was $85 bucks and it came with cheap Alum 4
gal pot and fryer. These were badly damaged and the burner stand had a dent
in the outer ring also. I asked for half-price, the Manager wrinkled his
brow and said he didn't think he could do that seeing that everything was
20% off for the grand opening--how about 50 bucks he said? I grinned
quietly to myself and said sure! ;<) This year prices have been lower, $63
at Lowe's, $55 at other places. I resold my old one for $40. The most
valuable part was the regulator it was 0-17 PSI 2 more PSI than the
replacement part I ordered from Cajun cooker. My 2-tier system uses the 17
PSI regulator and the old burner got the new regulator...
- ---------
Troy Hager <thager@bsd.k12.ca.us>
Discusses some very interesting points on evaporation rates I hadn't
considered before. My previous practice in doing 5 gal
all grain batches had me sparging to collect 6.5 gal and boiling down to
5.25 to yield 5 gal in the primary and .25 left in the
kettle and absorbed in the hops. That's 19%!! The same Raging Boil Syndrome
(RBS???;<) that Troy has. Trial and error
had gotten me to shorten my boil from 90 to 75 min to achieve a reduction
from 6.5 gal to 5.25 gal. So naturally when I
moved to 10 gal batches I plan to collect 13 gal and reduce to 10.5 gal
still doing a 75-80 min boil. I guess Ill have to
re-read Fix to see why reductions greater than 11% reductions are bad?
Does anyone else have any input on this?
What is wrong with 19%???
As long as your not over-sparging and getting tannin extraction due to low
pH, what is the harm in it?
Scottish and Scotch ales use 2 - 3 hour boils...My conversations with Rob
Moline indicated he had used longer boils to
reduce volumes and reach higher gravity's at LABCO...So what gives?
Any input from the pro's out there? Rob, you recovered yet?
Phil Wilcox
Poison Frog Home Brewery
Sec/Treas Prison City Brewers
Jackson, Michigan
------------------------------
Date: Wed, 6 May 1998 14:05:47 -0400
From: "Philip J Wilcox"<pjwilcox@cmsenergy.com>
Subject: Big 10/20
From: Philip J Wilcox@CMS on 05/06/98 02:05 PM
Hi again,
I just discovered the joy and euphoria of exceeding the 8k limit! Now I
know why Dave and Al do it so much, ITS FUN!!!! ;<)
Big Brew '98
Someone, I deleted who, was asking for more Big 12 experiences. Not ever
having drank Robs Big 12 I can't
comment on that, but what I think the intent was more news on the Big Brew
'98's ie. Big 10/20--and I did make 10 gal of
that on Saturday.
BTW Happy 20th anniversary AHA!!!!!!!!!
The Big Brew in Jackson was a hit, 5 of us from the Prison City Brewers
participated. The 6th couldn't make it. Oh well.
I easily fit 36 lbs of grain in my 1/2 Bbl. 40 would be possible but
recircing and sparging would be a real trick. Mashing
went well, at 60 min with recircing the latter half. The new $20 electronic
thermometer works much better than the cheapie $5
ones from gordon foods. Doesn't melt either. If its rated to 302F than it
should melt--right? With all of the other stuff
going-on I wasn't able to keep as good of a watch on my boil as I usually
do, I caught it "simmering" twice. As my CH4 tank
gets emptier the pressure goes down Btu's go down...I keep cranking it up
as I went....I ended up with more than 10 gals
of 1094 wort.
I did my best not to cringe in horror as I watched the newbie brewers using
funnels and cheese cloths to try to strain
out hops and spooge. I felt bad and helpless since my 6-gal easy masher pot
was at home...I didn't even have a copper
scrubby to put over my copper racking cane which I also didn't have...
The All-grainers finished up by 8:30 and we Pitched 2 cups/5gal of Fresh
yeast from the Brewery and then headed inside
the pub for Pizza and Beer! A Raspberry Lager, American Wheat, and a Bob
Lite were the 6th handles, A great
time was had by all. It was Prom night for a couple of area schools and it
was especially fun watching all the kids
coming and going all decked out in tux's and long dresses. One comment
seemed to reach agreement. Girls didn't look
like that when we went to Prom...especially that 6'8" Red Head! Yeouch!!!
Well, Rob Moline warned us that a raging fermentation was to be
expected....and the Nottingham we tapped out of tank#5
By the time we got back to our vehicles, Fermentation was IN PROGRESS!!!
and those that were driving home towards Battle
Creek were Mighty nervous about not having blowoff tubes in the car with
them!! We had a lot of fun! We all learned a
lot Some of us used grains for the first time! Others learned about the
trade off's of 10 minute sparging. We had a
great time! Sold some T-shirts for a fund-raiser and Picked up 6 new people
as potential members!
As for mine, at 4:00 AM I awoke hearing a POP! And immediately went, Oh
S)(*&T! In my exhaustion of unloading the brewery from my dads van at
Midnight by myself I barely had enough strength to carry my 6.5 and 5 gal
fermentors to the basement. I had left them there in the brewery corner
just sitting on the floor with their S-shaped airlocks still in place. I
got to the basement light switch and squinting not only from the time of
day, but from what I expected see...I turned it on and burst out
laughing!!! The Pop noise that woke me must have been a neighbor getting
shot down the street or something because both airlocks were still in
place. But, (there's always a but) The S-airlock's cap had blown off and a
3 inch geyser of foam was expelling from it! It was like Gillette came out
with a beige shaving cream can! I sanitized an orange blow off widget, and
got out a pair of C-clamps and my gallon jug.. The 6.5 gal one looked ok,
so I left it and crept back to bed. Slept right through my Alarm for church
in the morning...I awoke with another jolt, realizing I'd have to creep
into the choir loft late...I went to the basement to Iron my shirt and sure
enough, as timely as Old Faithful, the 6.5 Gal Carboy was erupting a
continuous stream of creamy smooth foam! I laughed as glanced my watch
while trying not to burn my shirt...It will be there when I get back from
church...
And it was, by this time I'd had some coffee. The brain was working
and it said to get the digital camera out. I don't have my own web site,
but Ill email the Jpegs to whomever wants to post them! Mt. Vesuvius and
Old Faithful!!! Do they make blow off Caps for 6.5 carboys? I know I don't
have one. It took me a while before I figured I could stuff my racking cane
in there and use that. I have about a half gallon of recondensed foam now
and the eruptions continue! Michael Lausin <soscc@cmn.net> is thinking his
primary fermentation might be done. and is considering pitching Champagne
yeast. AAAAGG Please don't, Its not done yet! Give it three weeks! then
rack and add Champagne yeast. Adding champagne yeast now will give it too
much food to eat and resulting more winy sherry-like off flavors than you
would have had. Patience, Patience, Patience.....When It comes time, proof
just like any other dry yeast. 2 cups 104F water 1 tbls sugar stir in yeast
and let set for 15 min. and pitch.
Rex HalfPenny of the Michigan Beer Guide stopped in at many Michigan Big
Brew sites and said he intends to put a tasting group together of those who
brewed this beast in about Dec-Jan. I can wait, Can you???
Phil Wilcox
Poison Frog Home Brewery
Sec/Treas Prison City Brewers
Jackson, Michigan
------------------------------
Date: Wed, 06 May 1998 14:31:26 -0500
From: "A. J. deLange" <ajdel@mindspring.com>
Subject: Alcohol/Aldehyde or Redox Redux I
Al K was interested in knowing a little more about the oxidation of
alcohols in beer. This is a classic redox reaction. The oxidation of an
alcohol to an aldehyde doesn't require the presence of oxygen - many
other oxidizing agents (such as melanoidins in the oxidized state) will
do. The "oxidation" in reactions of this type is actually the
the loss of hydrogen atoms (or, more strictly speaking, the loss of the
electrons the hydrogen atoms carry). As an example, ethanol is oxidized
to acetaldehyde by the loss of two hydrogen atoms:
ethhanol -----> acetaldehyde + 2H+ + 2e- +.197 V
which is written showing a hydrogen atom as a proton (H+) and an
electron
(e-).
For a generic alcohol
AcyHOH -----> AcyO + 2H+ + 2e- + Vacy
"V" is measured in volts and represents the tendency of the reaction to
take place. It is proportional to the change in energy of the reactants.
Vethanol = + .199 V, written here as an "oxidation potential", is found
in every biochemistry book though it is standard practice to print
-.199 volts and call it a "reduction potential". I don't have any values
for other alcohols but, in common with Dave B, have no reason to expect
that they would differ appreciably from the value for ethanol.
To summarize thus far in terms of the way Al posed the question:
- The tendency of an alcohol to be oxidized isn't really a matter of
affinity for oxygen but rather a tendency to lose hydrogen atoms (and,
in particular, the electrons they carry).
- The tendency of various alcohols to lose hydrogen (electrons) is
modest and is probably about the same for most alcohols.
There is another half to the problem. Where do the hydrogens (electrons)
go?
Something must take them up and this is the role of the oxidizing
agent. For example when your liver processes alcohol , the oxidizing
agent known as NAD+ takes up hydrogen and in doing so is said to
be "reduced" which is the opposite of oxidation:
NAD+ + 2H+ +2e- ----> NADH + H+ -.320V
NADH is the usual symbol for reduced state NAD. Oxygen is, of course, an
excellent oxidizing agent and is thus readily reduced:
1/2 O2 + 2H+ + 2e- ---> H2O + .816V
The voltages indicate that oxygen is a much more powerful oxidizing
agent than NAD+. This time, the voltage is the reduction potential just
as is tabulated in textbooks. Thus good oxidizers have high (more
positive) reduction potential.For the generic oxidizing agent
Oxy + 2H+ + 2e- -----> OxyH + H+ + Voxy
Voxy means the reducing potential of the oxidizing agent. Vacy means the
oxidizing potential of the reducing agent (alcohol) and yes, I know this
is as confusing as hell.
Note that we have modeled the behavior of the general oxidizing agent
like that of NAD+. We do this because it is standard practice among
biochemists to write all redox pairs in terms of electron pairs rather
than with reference to single electrons because so many of the redox
reactions of biochemistry are like that of NAD+/NADH and involve pairs.
These reactions also frequently involve a proton (H+) and the
consequence of this is that pH is a factor in many biochemical redox
reactions as we shall see. Also note that the potentials we have given
are at physiological temperature and pH.
Adding the oxidation and reduction half reactions we get :
AcyHOH + Oxy -----> AcyO + OxyH + H+ + Vacy + Voxy
For ethanol with NAD+
ethanol + NAD+ -----> acetaldehyde + NADH + H+ - .123 V
For ethanol with Oxygen
ethanol + 0.5 O2 ----> acetaldehhyde + H2O + 1.013 V
Thus, under standard conditons, the reaction involving oxygen is much
more energetically favorable than the one involving NAD+ as oxygen is a
stronger oxidizing agent. Under other than stardard conditions reaction
will procede until
.03(-Vacy - Vox) + log([aldehyde]/[alcohol]) + log([OxyH]/[oxidizer]) +
(7 - pH) = 0
where [ ] represents the molar concentrations of aldelyde, alcohol,
oxidizer and reduced oxidizer. I'll just bet there's a reversed sign in
there somewhere. By looking at this we see that, for example, if more
oxidizer is made available [other things equal], the second log term
decreases and so the first log term must become larger thus implying a
larger level of aldehyde (as we would expect). Similarly, if Vox becomes
larger (i.e. a better oxiding agent is involved) the aldehyde
concentration must go up realative to that of alcohol so that the log of
the ratio increases by as much as Vox was increased. Note that if
oxygen is the oxidizing agent the pH dependence drops out.
Summary points here are:
- The extent to which the reaction ( conversion of alcohol to aldehyde)
takes place depends on the concentration of alcohol, the amount of
oxidizer present and, in many (I'd say all except where molecular oxygen
is involved) cases, pH.
- The extent to which the reaction takes place depends not only on the
amount of oxidizer but on the strength of the oxidizer and on the
oxidation potential of the alcohol as well. The larger the oxidation
potential of the alcohol and the larger the reduction potential of the
oxidizer the more aldehyde will be present at equilibrium.
------------------------------
Date: Wed, 06 May 1998 14:33:37 -0500
From: "A. J. deLange" <ajdel@mindspring.com>
Subject: Alcohol/Aldehyde or Redox Redux II
What we have talked about so far are equilibrium conditions. Biological
redox reactions often reach equilibrium very slowly, if ever, unless
suitable enzymes are available (and that's why enzymes are so critically
important in our yeasts and even our bodies). This means that though a
staling reaction may be energetically feasible it may never take place
or may take place so slowly that we don't encounter it for a long time.
This is desireable in beers we don't want oxidized (drink 'em quick) and
a nuisance in those where we do want vinous or sherry notes as we
must often wait months for those flavors to form.
Dave and Al discussed melanoidins as reducers and oxidizers. Our
equiilibrium condition could be written:
.03(-Vacy - Vmel) + log([aldehyde]/[alcohol]) + log([MelH]/[Mel]) + (7 -
pH) = 0
where MelH represents the reduced state of the melanodin whose oxidized
state we denone by Mel. Vmel is the reduction potential of the
particular melanoidin under consideration. If oxygen has been excluded
in packaging or if yeast are included in the bottle and scavenge the
oxygen then Mel/MelH could be the major determinant in how much
oxidation of alcohols takes plave. If there is lots more reduced state
melanoidin than oxidized state then log([MelH]/[Mel]) is large and the
ratio of aldehyde to alcohol is low or will decrease over time as
equilibrium is approached. Conversely, if the melanoidins are mostly in
the oxidized state, aldehyde to alcohol ratios will increase. Thus the
goal of HSA prevention is [MelH] > [Mel] and the Nernst equation (that's
what this thing is called) shows why that is desireable. The actual
effect of [MelH] > [Mel] depends on Vmel, i.e. the reduction potential
of the particular melanoidin.
Finally, Dave attributed a sherry taste to acetaldehyde. In my
experience acetaldehyde has a fruity, apple-like taste. Acetadehyde is
easily experienced in Budweiser whose yeast strain leaves a lot of it
behind in the beer. The low malt and hop levels make it easy to taste
and smell. Note that the
ethanol + NAD+ -----> acetaldehyde + NADH + H+
reaction is, as we have mentioned, the one that takes place in your
liver when alcohol is metabolized. Hangovers are a combination of
acetaldehyde poisoning (hence Bud's nickname "hangover in a can") and
excessively "reduced state" of the liver which means that there is too
much reduced state NAD (i.e. NADH). By the way, the enzyme here is
alcohol dehydrogenase whose name suggests very clearly that oxidation
(dehydrogenation) of alcohol is what is being catalyzed.
This bollixes up all manner of the body's redox reactions in a way which
I hope this post will have helped you to understand to some extent.
------------------------------
Date: Wed, 6 May 1998 23:32:31 -0700
From: Troy Hager <thager@bsd.k12.ca.us>
Subject: Boil Roll and Evaporation Rate
HBDers,
Thanks for the overwelming response that I have gotten on this topic. Many
have commented on similar findings with their setup and wonderings of what
to do about it, if anything. The idea of a partially covered boil seems to
mimic the pros and might be something to look into in more depth.
________________________________________
Scott Murman has some interesting views and wonders about the origin of the
10% rule:
> "The best general recommendation is an evaporation rate
> of 9-11%. In all cases, avoid evaporation rates in excess of 15%" and that
> "also striking is the number of times the negative effects from (excess
> evaporation) are incorrectly identified as problems in fermentation."
I'd say this is a bunch of hooey. And probably some poppycock thrown
in as well. This is a typical Fix'ism; he makes a statement and then
backs it up with nothing. The only negative from a stronger boil that
I can think of is a greater energy ($$) usage. Carmelization, hop
isomerization, protein coagulation, etc. can all be considered
beneficial.
This business about 10% evaporation being the ideal probably comes
from the commercial brewing world, and is meant to be a *minimum*
guideline. Since they're concerned with money, they will want to use
the minimum amount of energy possible. If they are getting a 10%
evaporation rate, then they can be sure they're "OK", and using about
the minimum energy possible. For their volumes, and number of
batches, the savings between 10% and 15% evaporation is non-trivial.
Scott
(getting 20% evaporation and wishing for more)
_____________________________________________
It is true that Fix (and literature that I have read stating this 10% rule)
does not give any references to where this information was obtained. Has
there been any studies on this topic? I am wondering - Who has "incorrectly
identified" excess evaporation "as problems in fermentation" and why should
rates of more than 15% be avoided "in all cases." Perhaps the authors Fix
would like to comment and validate these statements to prove that Scott's
notion of a "typical Fix'ism" doesn't exist.
Might there be some truth in that a little is better that a lot in the case
of "thermal loading" as Fix terms it. Might there be negative effects in
the Maillard reactions (which Fix does mention) and even over-extraction of
hops (phenols maybe??) due to excess heat at the boil??? I'm just grabbing
at straws here. Someone with more knowledge, preferably Fix themselves,
please step in and enlighten us on this topic!
Troy A. Hager
2385 Trousdale Drive.
Burlingame, CA 94010
259-3850
------------------------------
Date: Wed, 6 May 1998 16:06:16 -0400
From: "Taber, Bruce" <Bruce.Taber@nrc.ca>
Subject: chocolate Porter (good head)
There has been some talk lately about the oils in chocolate ruining
head retention. Here's my data point.
I made a Chocolate Porter (yes a Porter, not a Stout. It's my beer
and I can call it anything I want). I used Baker's Cocoa Powder instead of
chocolate since it seems to have less oils. I split 5 liters (1.3 US gal.)
off my batch of Porter near the end of the boil, added 9 tbls. of Cocoa to
it, and boiled 15 min.
There was quite an oil slick on it during fermentation. I tried to
leave most of it behind during racking but I'm cheap and I hate to waste
beer so I wasn't too careful.
The result was that the beer has a good head. Not quite a Guinness
head, but one that is moderately thick and will last a good 10 min.
The taste is subtle but noticeable if you know it's there. I can do
a direct comparison to the same Porter without chocolate in it and I can say
that it is a nice addition.
I also tried adding lactose to some of the bottles since I thought
that the additional sweetness would bring out the chocolate flavor a bit
more. I added lactose at 11g / liter (1.5oz. / US gal). I found that this
was an improvement to the flavor.
My other suggestion is to keep the hop bitterness and flavor a bit
low. My base Porter had an IBU of 36, but by skipping the flavor addition
in the last 15 min. I had an IBU of 31 for the chocolate Porter.
Isn't brewing fun!!!
Bruce Taber
Almonte, Ont. Canada
bruce.taber@nrc.ca
------------------------------
Date: Wed, 6 May 1998 16:23:32 -0400
From: dbgrowler@juno.com
Subject: kettle evap rates
Troy brings up issues that have caused some serious navel gazing here in
my brewery. For many years, I happily boiled the bejesus out of my wort,
7 gal down to 5.5 over 90 minutes, enjoying my high alpha utilization,
excellent kettle break, and award-winning finished beer. After reading An
Analysis of Brewing Techniques, I, too, started worrying. I asked several
professional brewers about it; I can summarize their replies as "I
dunno." Then I went back and looked at my logbook. Though I brew plenty
of beers of all types and colors, the medal- and ribbon-winners were all
dark beers. Hmm. Reviewing score sheets on lighter beers showed some
indefinite remarks like "watch sanitation" with no specific off-flavor
mentioned, incorrect guesses at the yeast strain used, fermentation
temps, pitching rates, etc., which is quite in line with Dr. Fix's
observations. It appears that the effects of excessive thermal stress are
subtle for my system, such that they are not noticeable (or more in line
with the flavor profile) in the heavier, maltier beers. I've since brewed
two light Munichs serially, the second one with a less vigorous boil, but
otherwise unchanged. The results? I dunno... A partially covered boil
could be the ticket, but I foresee a learning curve perfumed with the
acrid smell of caramelized sugar. I think the key phrase in Fix's book is
"find a balance"; balance between adequate kettle reactions and thermal
stress, and also between attention to detail and a relaxed mental
attitude.
Mike Bardallis
Trying very hard not to be too anal, in Allen Park, MI
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------------------------------
Date: Wed, 6 May 1998 15:43:08 -0500
From: rlabor@lsumc.edu (LaBorde, Ronald)
Subject: RE: Confusion over delta T
From: "Matthew J. Harper" <matth@progress.com>
Subject: Confusion over delta T
>I'm in the planning process for RIMS construction.
> . . .
>I've been contemplating a non-standard heating chamber using an
>external mounted (wrapped) heat source (tape or ceramic) that
>gets wrapped around the pipe. However, some of these beasties
>have pretty high temps. A good flow rate would help reduce the
>(proposed) risk, but I dunno. Has anyone tried this method?
If you want something really different, try this:
Use a stainless steel coil as the heating chamber, with the mash liquid
and pump connection by non conducting plastic tubing, then power the
coil with high amperage low voltage AC current.
You will probably need to rewind a transformer by changing the secondary
winding to a very large single or several turn conductor, then this will
connect to your stainless heating coil. I once played around with a
transformer like this, with a few turns on the secondary, could make a
coat hanger glow bright red! You will need to experiment, with a lot of
cut and try, and maybe get an electrician to assist in the design. You
can start by finding some high power battery charger, or an old welding
transformer as the source for a transformer to rewind.
Ron
Ronald La Borde - Metairie, Louisiana - rlabor@lsumc.edu
------------------------------
Date: Wed, 06 May 1998 17:04:27 -0400
From: "Capt. Marc Battreall" <batman@terranova.net>
Subject: AHA Nationals
Hello All,
Seems that there is alot of thread regarding styles and guidelines
lately so the time seems right to ask a few questions directed at the
BJCP's out there. These are not about styles, but more so about the
competition procedures. I plan on entering a few beers in the upcoming
AHA Nationals and was wondering about the actual judging itself.
I pretty much understand the procedures that are followed in the actual
judging itself from what I have read and witnessed at small
competitions. My questions are:
1. When the beers arrive at the site are they kept refrigerated?
2. If so, are they kept cool, or more appropriately, kept at the proper
temperature suitable for the style?
3. If not, are they brought to the temperature prior to judging?
4. Some, if not most beers' flavor is altered markedly if not served at
the proper temperature as most will agree. Do the judges take this into
consideration at the time of judging?
5. Short of going to the competition in person, is there any way to
receive the judging results/comments if you should not happen to place?
I understand that there will be ALOT of beers to be judged and this is a
tremendous undertaking, even for the most experienced judge. I also
understand that the beers will all pretty much undergo the same
treatment and handling preventing any one brewer from having a unfair
advantage. I am going to enter my beers regardless of the methods of
handling and judging because I am proud of what I have brewed and look
forward to the competition. Just had a few questions to satisfy my
curiousity. Thanks in advance.
Marc
- --
Captain Marc Battreall
Backcountry Brewhouse
Islamorada, Florida
------------------------------
End of HOMEBREW Digest #2707, 05/07/98
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