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	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
		Digest Janitor: pbabcock at hbd.org


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Contents:
  yeast oxygenation/stir plates (ALAN K MEEKER)
  Re: metallic taste in reconditioned keg (Dylan Tack)
  Big Beer Efficiency problem? Or no problem? ("Michael Eyre")
  wooden casks for homebrewing; use furniture legs (Raj B Apte)
  Re: Hop Isomerization ("Greg 'groggy' Lehey")
  Growing hops (Bill Velek)


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Date: Sun, 12 Feb 2006 22:57:48 -0500
From: ALAN K MEEKER <ameeker at mail.jhmi.edu>
Subject: yeast oxygenation/stir plates

John Peed asked about the role of oxygenation and stir plate usage
during yeast starter prep. Basicaly, oxygen is required for the 
synthesis of certain components of the cell membrane (not the cell 
wall which surrounds the cell membrane). During the actual 
fermentation, where oxygen is (hopefully!) excluded, the concentration 
of these compounds limits the number of cell divisions that can take 
place since the compounds are divided up between the mother cell
and the daughter cells. Once the lower limit required for membrane 
function is reached, cell division ceases. In addition to limiting the 
expansion potential of the yeast population, depeltion of these 
membrane compounds can lead to less healthy and robust yeast
which can negatively affect the fermentation, particularly if it is a 
stressful one (e.g. high gravity).

How does a stir plate speed starter growth?

The mixing action of magnetic stirrers promote starter growth in a couple 
of ways. For one, it helps aerate the starter wort, which allows the yeast
to maintain healthy membranes and continue dividing during the starter
growth. Of course this does depend on having air or oxygen input to
starter. Continuous mixing also helps to remove CO2 generated by the
yeast and keeps the yeast cells suspended and mixed well with the 
nutrients in the wort, all of which encourages healthy and rapid yeast 
growth.    

Is there risk of oxidation by pitching the whole starter?

Well, there's no risk of oxidizing the main wort by addition of the starter
as this is the stage in whgich you want to aerate the wort anyway. 
However, one would think that the starter wort itself should be highly
oxidized and that you woudn't want to add this to your main wort at
pitching. I thought this myself, but I've heard from enough people
who do this (even had some of their beers) who say it does not
hurt the finished beer, that I now believe it doesn't adversely
affect the final quality. Why this is, is not exactly clear to me. It may
be that the compounds generated during the starter growth are 
metabolized by the yeast during the several days of primary
fermentation, or, if volatile enough, may be "scrubbed out" by all
of the CO2 generated.

Alan Meeker, Baltimore MD


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Date: Mon, 13 Feb 2006 10:07:32 -0600
From: Dylan Tack <dylan at io.com>
Subject: Re: metallic taste in reconditioned keg

> Date: Sun, 12 Feb 2006 19:37:08 -0500 (EST)
> From: Aaron Martin Linder <lindera at umich.edu>
>
> I don't know what the residue was. Perhaps a layer of metal oxide
> leached  off of the keg after SABCO's processing.
>

I'm not sure exactly how Sabco reconditions them.  But it's possible
that there is some raw metal exposed.  Normal stainless still has a
thin, invisible layer of chromium oxide, which is what gives it its
corrosion-resistant properties.

You might try "passivation", which is basically washing it with weak
nitric acid to encourage the formation of this layer.  It will form
spontaneously without your help, but there may be advantages to using
the acid (such as removing iron compounds from the surface).

 -Dylan




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Date: Sun, 12 Feb 2006 11:45:43 -0800
From: "Michael Eyre" <meyre at sbcglobal.net>
Subject: Big Beer Efficiency problem? Or no problem?

Hey all.
   
  Brewed up a larger than normal beer (than our usual) this weekend.
About 32 lbs total if memory serves. 25lbs of Pale 2row, a pound and a
half of Roasted Barley and Dark crystal 120L and a bit less than the
above of chocolate malt too. A couple lbs of Wheat and Flaked Barley
rounded it out. A 10.5 gallon batch it turned out to be at 1.076, when
we were shooting for 1.085. We're usually right on the nose accurate
with our smaller brews (within' a point or three...) so we were
wondering why this one fell so short of what we had hoped to get. Is
there anything about bigger beers and an efficiency curve? We mash in a
1/2bbl keg with a slotted pipe manifold, FWIW. Like I said, we're
usually right on the money, but really fell short this time. We did have
a bit of a stuck mash, but we figured that out after about 1/2 hour to
45 minutes or so... really slow runoff after that. Batch sparge too, if
that matters. Our efficiency numbers are usually 80-83%, and this time
it was more like 71% efficient. Anything I mentioned here strike a chord
with any one???
   
  As a side note, this beer was pitched onto the yeast slurry from a
Safale US-56 dry stout of 1.045O.G. that I was asking about last week.
Fermentation went of like a bomb in the primary! Thanks for the
suggestions to use it, for all that responded. We'll let you know how
she tastes in a while.
   
  Mike



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Date: Mon, 13 Feb 2006 11:48:27 -0800 (PST)
From: Raj B Apte <raj_apte at yahoo.com>
Subject: wooden casks for homebrewing; use furniture legs

All,

Wooden barrels may serve to modify beer in several ways:

1. oak flavour. you can get this cheaply from chips.
2. flavour of whatever was in the barrel before.
3. micro-oxygenation of the beer
3a. micro-oxygenation of the beer with Brett or other
critters.

For 1 and 2, you are on your own. Use some chips or chips
soaked in brandy &c. For 3 and 3a, I've gone through the
numbers on my site (search apte flemish sour ale).

Tank  	Volume [L]  	O2 cc/L.year
Burgundy barrel 	300 	8.5   
Rodenbach tank, wood, small 	12,000 	0.86
Rodenbach tank, wood, large 	20,000 	0.53
HDPE bucket 	20 	220      
Homebrew barrel 	40 	23      
Glass carboy, 30cm vinyl immersion tube 	20 	0.31
Glass carboy, silicone stopper 	20 	17      
Glass carboy, wood stopper 	20 	0.10

As you can see, if trying to reproduce Rodenbach or lambic
(burgundy barrel or larger), you want 1-10 cc O2/L.year.
Small barrels will give a few times more than that, and
plastic barrels will give WAY too much oxygen.

The solution that I use to this problem is to bung by glass
carboys with oak dowels. The dowels are auto-clavable,
toastable, and--with a bit of teflon tape--may seal the
cask well. Don't do this if there is any chance of
pressurizing the carboy!!! The dowels I use are sold for $2
for furniture legs--cheap american oak. A few days soaking
removes much of the oak taste (inappropriate in sour ales
to style). According to the table, they allow too little
oxygen, but bungs are end-grain, which may have 5-10x more
diffusivity. Actually, I suspect its more than that.

I also have a few 60L oak barrels from morebeer.com. They
work pretty well.

Don't blame me if your carboy explodes. I have 10 bunged
carboys at my place and haven't had a problem yet (some are
2 summers old).

best,
raj




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Date: Tue, 14 Feb 2006 08:31:27 +1030
From: "Greg 'groggy' Lehey" <grog at lemis.com>
Subject: Re: Hop Isomerization

On Saturday, 11 February 2006 at  8:35:07 -0900, Martin Brungard wrote:
>
> John Peed recently posted an item regarding hop isomerization that
> should be expanded upon.

Thanks for the information.  It has answered some questions I haven't
got round to asking yet.

> Whole hops do require a rolling boil in order to help expose and
> burst the lupulin glands.  But the degree of the exposure and the
> degree to which the lupulin glands were burst during harvesting and
> packing will always be in question.

While this is doubtless true, isn't this taken into account by the
means of measurement?  And doesn't it apply equally to pelletized
hops?

> The degree of utilization of alpha acids is very much in question
> when using whole hops.

Agreed, but not for the reason you state above.

So: when using whole hops, should they first be shredded?  I've tried
putting the hops into a blender, adding some wort out of the pot, and
blending them.  The results are relatively inconclusive, of course,
but it seems a reasonable approach.

Greg
- --
Finger grog at lemis.com for PGP public key.
See complete headers for address and phone numbers.


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Date: Mon, 13 Feb 2006 18:47:37 -0600
From: Bill Velek <billvelek at alltel.net>
Subject: Growing hops

In reply to my inquiry about supports for growing hops, Stencil wrote in 
HBD#4947:

 > I use 20-foot masts, made of 2-1/2 and 3-inch pvc pipe - just
 > slip-assembled, no cement - that are socketed on re-bar pins.

snip

What, exactly, do you mean by "socketed".  Another poster, different 
forum, does something similar; he has a pipe set in the ground, uses a 
tall pipe of the same diameter, and a length of pipe (larger diameter) 
as sleeve to join the two pieces.  When it's time to harvest, he lifts 
the mast out of the larger supporting sleeve, and lowers it to the 
ground.  I presume two people would does this together, with one on each 
mast.

 > A pair of masts supports a 30-ft spanwire of braided para cord from
 > which the jute bine-support lines dangle.

snipped other details of design.

Thanks, Stencil.  Good info that I can use if I go that way.  I've also 
been reading posts from folks who say that it isn't absolutely necessary 
to have the hops grow straight up, and some of them use a trellis or 
arbor.  One fellow who does that said that he gets plenty of horizontal 
growth and just stands and harvests the hops from overhead.  That 
appeals to me, too, because several people have written that it is 
better to not wait until the end of the season to begin harvesting.  So 
I'm still trying to work this out, weighing all of the pros and cons.

Cheers, Bill Velek
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