---

	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:
  Alkalinity/Modes and Nodes/Tannin in Cyser/Stirring (AJ)
  yeast models/amino acids/sterol - health concern. ("Steve Alexander")
  Pitching Rates (Amber/Bruce Carpenter)
  Cylindro-conical Plastic Fermenters ("Eric L. Peters")
  Refrigerating beer / constant aeration of starer / survival rates of stored yeast / Hot Side Aeration ("George De Piro")
  Stirring starters (Domenick Venezia)
  Oatmeal Stout ("charles beaver")
  Hop growing question (Denis Barsalo)
  glass carboy ("Darren Robey")


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Date: Sat, 29 Aug 1998 09:12:40 -0400
From: AJ <ajdel at mindspring.com>
Subject: Alkalinity/Modes and Nodes/Tannin in Cyser/Stirring

>From Lou: Heavner

     >if you are not going to explain them, it might be easier to
     >just say "multiply the alkalinity by 1.22."

Ah yes. Good point. Alkalinity in ppm as CaCO3 is 50 times the
alkalinity in milliequivalents per liter, i.e. the number of
milliequivalents of strong acid, required to bring a liter of the water
to pH 4.3. One milliequivalent of acid is required for each
milliequivalent of bicarbonate present (H+   + HCO3- --> H2CO3). The
equivalent weight of bicarbonate is 61 mg/mEq.

* * * * * * * * * * * * * * * * * * * * * * *

Not that it really matters that much to brewers but I think Mark T A
Nesdoly may be confusing "nodes" and "modes". A node is a place where
the E-field is 0 (or nearly so). Where the nodes occur depends on the
configuration of the cavity which determines the mode of propagation
within it. The purpose of the mode stirrer is to change this
configuration thus changing the mode and moving the nulls (nodes)
around.

* * * * * * * * * * * * * * * * * * * * * * * * *

Jebbly suggests adding raisins to mead musts to obtain a tannin taste. I
guess I'm confused as to why anyone would want to do this though I've
seen it suggested that grape tannin be added to meads. I've got a cyser
with polyphenols at 90 mg per liter and a sack at 16 (these represent
the totallity of my mead making BTW). These were made at the same time
(back in Jan) from the same honey. No tannin was added. The cyser is
just plain phenolic rough! The sack is lovely. Will the cyser mellow
with time? Is the mellowing the same as in beer, i.e. complexing and
precipitation of the polyphenols? If so, why put it in in the first
place?

* * * * * * * * * * * * * * * * * * * * * * * * * *

Stir plates benefit growth in starters by keeping the yeast in
suspension and thus bathed in the nutrients of the broth. This is so
whether they are in growth or fermentation phase. Clearly, external
oxygen must be supplied or, as the other posters have observed, the
broth will simply become blanketed with CO2. Mark Bayer asked how yeast
would grow if an airstone supplying air or O2 were in the broth and the
broth on a stir plate. The answer here is that the froth formed by the
airstone would make a horrible mess. The oxygen or air needs to be
supplied periodically in order to allow the foam to subside or an
anti-foaming agent must be used.  Dreamers may consult the Cole - Parmer
caltalog under "Fermenters" where devices costing as much as a good used
car are touted. These consist of a vessel with a stirrer equipped with
pH, DO and foam sensors connected to devices which meter O2, buffers and
antifoam into the vesses as required. This obviously represents the
ultimate but I expect the innovative could kluge up arrangements equally
as effective. My thoughts along these lines have been to use a small
inverted carboy (they used to sell or perhaps still do a doodad that
caps them upside down) with an airstone connected to an O2 bottle hooked
to a timer and valve that would provide multiple short bursts of O2
every 10 minutes or so. I think that the agitation produced by the gas
bursts might be enough to keep the cells in suspension to the point that
a stir-plate wouldn't be necessary.

Another thought is to use a stir plate with a flask hooked to an
aquarium pump in such a way that the air stream does not pass through
the broth but just sweeps out the CO2 released. In this case exchange
through the surface of the liquid would be enhanced by the stirring.



Return to table of contents


Date: Sat, 29 Aug 1998 09:40:53 -0400
From: "Steve Alexander" <steve-alexander at worldnet.att.net>
Subject: yeast models/amino acids/sterol - health concern. 

Jim Liddel wrote ...

>The Ramirez articles in
>JIB and B and B read this way.  "maximum alcohol in minimum time",
>"industrial brewing".  And they used 16 P wort.

I have access to the JIB article only at the moment, they do not spec the
SG anywhere in the article.  The abstract of "A FLAVOUR MODEL FOR
BEER FERMENTATION" reads:

" A new beer fermentation model is developed based on fundamental
 knowledge of biochemical pathways.  The model can be subdivided
 into a growth model, an amino acid model and a flavour/aroma model. 
 Experimentation allowed for accurate model parameter identification. 
The results demonstrate the capability to accurately accurately describe
batch beer fermentation dynamics."

This paper is decidely about modeling the important yeast parameters
in terms of uptake and byproducts.  It is not about maximum alcohol,
minimum time and there is no mention of these factors.

This paper is the successor to papers like Ayrapaa, Nordstrom and to 4 
decades of chemostat experiments by guys like Young and others -tho
it's more about modelling the fermentation and deriving valid math
representations rather then uncovering new pathways.  Basically they
propose a set of equations to model quite a few beer parameters -
sugar & amino uptake, specific esters, fusels, VDKs.  They then run
batch fermentations at several temps measuring these parameters
and use the data to create coefficients for the model.  The resulting
model curves match the real data quite closely indicating that there is
something right about the model equations. The coefficients only apply
to the given yeast, and the other undescribed wort parameters - so the
specific number aren't important.  That the model works so well is
important and tells us that the equations do describe, isobutanol
production for example quite accurately in terms of yeast mass,
yeast specific growth and valine concentrations.

>My point is that this is
>research that is geared, as is most beer research. towards making light
>lager in 900 barrel batches 24 hours a day 7 days a week.

So what ?  Are you saying the model doesn't apply ?  On what basis ?
The biochem equation date back to Ehrlich and Ayrapaa from the
1906-1970 and have been verified in a number of ways and under
many conditions.  To my non-professional eye almost all of the terms
derive from simple kinetic models or from the Michaelis-Menten model
that described enzyme catalysed reactions.  What do you propose is
different in HB that invalidates the result ?

As far as I'm concerned a negative finding, that the curves didn't match
would indictate the the model was incorrect or incomplete.  One can still
argue that the discrepancies between model and data represent
an imperfect model, and also measurement difficulty.  Some of the
VDK models for example are "weak" IMO.  Still the result must be
considered an impressive demonstration that certain biochem pathways
have been successfully accurately modeled.

>Granted some of
>their stuff is valid but Ramirez, based on his  CV is not a brewing
>scientist.  he is into modeling and process control.

The authors are from the Chem.E. dept, but the model is of yeast,
not an industrial fermentation operation  - tho' there is clearly cross
applicabilty.  The model describes how yeast work.  This is a
necessary prereq' for process control, but that subject is not
discussed in this paper.

As for the "some of their stuff is valid" comment.  I guess this means
you have evidence to refute parts of it.  Would you care to describe
what is in error and give a citation ?  I'm not arguing that Gee and
Ramirez 1994 paper is the last word on the issue, nor that their
model represents a perfect fit to the data , but the authors don't
claim this either. To dump on a peer reviewed journal article,
particularly one so recent, without any description of why or
reference is bogus IMO.  Perhaps you have a good reference
refuting points - if so I'd sincerely like to hear about it.  Otherwise
it's you opinion versus the IoB, and I'm afraid I'll have to side with
reviewed literature from a highly respected institute.

Lou.Heavner at frco.com asks ...

>     BTW, that wouldn't be Fred Ramirez of CU in boulder, would it?

Yes it is. W.Fred Ramirez and Douglas A.Gee both of UofC Boulder
wrote the article in late 1993.

- --

Where to get valine, leucine, isoleucine.  I'm not seriously suggesting
this (yet) but the idea is that at higher concentrations these can reduce
levels of n-propanol, isobutyl alc., 2-methyl-1-butanol and isoamyl alc. 
perhaps despite underpitching.  It may also reduce levels of
phenyl-alcohols such as tyrosol, tho' this is not covered in the paper
above.  You can get these at health food stores as well as chem supply
houses - not cheaply tho'.

- --

IMPORANT WARNING: Jim Liddel mentioned the addition of ergosterol
as a yeast growth supplement.  Ingestion of chalciferous ergosterol
(vitamin D) can cause liver and CNS problems and corneal opacity at
continued ingestion rates of 1mg per day.  Yeast growth might require
4mg/L to replace normal O2 levels so as you can see seeding your
wort with high levels of sterol might cause serious health problems
to the consumer if the yeast fail to remove the sterol. This may be a
useful starter technique, particularly if you (as Jim does) remove the
supernantant 'beer' before pitching.  Tho' as Jim pointed out privately
 - "air is cheap".  Also sterol addition alone doesn't satisfy the UFA
req of yeast.

Steve Alexander






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Date: Sat, 29 Aug 1998 09:33:01 -0500
From: Amber/Bruce Carpenter <alaconn at arkansas.net>
Subject: Pitching Rates

Hello,

I have a couple of questions for the group concerning pitching rates.
First, a little info. My current procedure is to start with a Wyeast
suited for the style of beer I plan to brew. I create a starter based on
nutrient pack instructions. I then add to this starter the two small
packs of dry yeast included in the beer kit I have purchased. The main
reason I add the dry yeast is due to the extensive discussion about
underpitching and that some believe that 1 package of Wyeast is not
enough yeast. And after all, the dry yeast comes with my beer kit, so it
is no extra expense. Questions: 1. Does this procedure have any striking
advantages or disadvantages? 2. Am I "adulterating" my beer with 2 types
of yeast and violating a purist's code?

The musings of a newbie, thanks for any help. Email welcome.
Bruce


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Date: Sat, 29 Aug 1998 09:26:42 -0500
From: "Eric L. Peters" <E-Peters at csu.edu>
Subject: Cylindro-conical Plastic Fermenters

Please excuse me if this topic has been discussed to death, but I am
interested in upgrading my brewing setup, and I am curious about the
cylindro-conical fermenters that I have seen advertised. One (the Conical II)
is sold by South Bay Homebrew Supply, and the other by Mini-Brew Systems.
Does anyone have experience with either (or both) of these? Are they
worthwhile (I am primarily interested in them because of their apparent
usefulness in trub removal and the ability to transfer without siphoning. I
am less interested in harvesting yeast)? If so, any opinions on which system
is better?

TIA

Eric Peters mailto:E-Peters at csu.edu




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Date: Sat, 29 Aug 98 10:49:46 PDT
From: "George De Piro" <gdepiro at fcc.net>
Subject: Refrigerating beer / constant aeration of starer / survival rates of stored yeast / Hot Side Aeration

Hi all,

Lou noted that my recent list of things that are bad for beer did not 
include
warm storage of finished beer.  I knew I forgot some important stuff.  
I'm sure
there's much more.

It is second nature for me to keep finished beer cool.  It is incredibly 
important.
Before I expanded my refrigerated space I would ice kegs for serving 
only.
The beer got pretty bad pretty fast at >78F (25C).  Over a few weeks you 
may
be OK at summertime room temperature IF you avoided things like oxygen 
pickup
and microbial contamination, but those are two big "ifs."

Some beers do well if kept at 50-55F (10-12.7C), particularly 
bottle-conditoned
strong beers or some of the more complex-tasting styles.  That 
temperature
range should be the maximium, though.  I keep lagers at 36F (2.2C) (and 
most of
my ales, too).

The higher the temperature, the faster all the chemical reactions in beer
 will occur.
Staling will definitely occur in a much shorter time.  Note:  this is 
another one of
those rare times where the word "always" is appropriate.
- ---------------------------------------------------------------------
Mark (and others) ask about constant aeration and stirring of the 
starter.  Mark
specifically asks if an aquarium pump can be used to aerate the starter 
while stirring.

Yes, it most certainly can.  The use of a 0.2 micron filter will ensure 
sterility of the air.
One warning, though:  the yeast MUST have a food source during aeration 
or they will
start to use up their glycogen.  Don't constantly aerate if you can't 
feed them regularly.

Stirring the yeast not only helps reduce CO2 levels in the liquid, it 
helps keep
the yeast suspended.  This allows them to do their work faster.
- ---------------------------------------------------------------------
Charley asks about how long yeast can survive in cold storage under wort.

At Siebel we were told to use your yeast within a week.  I checked this 
at home.
I had two strains (Wyeast 2206 and an ale starin that I don't recall). 
 I had been
keeping them both at 36F (2.2C) and feeding them fresh wort every two 
weeks.
Staining with methylene blue showed ~50% of the cells picking up the 
stain after
about a month.  That's bad.

Pitching a yeast cake in that condition will actually provide more live 
cells than most
homebrewers pitch, but you will also be pitching many dead cells (that 
can give a yeasty
off-flavor to the beer) and the live cells probably aren't at their best.

You can pitch them (I have done this), but be aware of what the effect 
may be on your
product.
- --------------------------------------------------------------------
There has been some talk about Anchor Brewing and HSA in their process. 
 They are not
the only brewery that recognizes this as a problem for their beer.

Deschutes (Bend, OR) had (in Jan. 1996) a whirlpool tank with a welding 
defect
that caused aeration of the hot wort.  The brewer told me that this was 
the biggest factor
limiting the shelf life of their beer (I specifically asked about the 
shelf life of their product).

As I said before, HSA is not the worst thing on the planet, but it is not
 good.  It is also
one of the single most simple things to avoid, so why design your system 
without
taking it into consideration?

I'm not saying to work in an inert atmosphere, but when faced with the 
question, "Should
I let the hot wort drop 2 feet from the lauter tun outlet into the grant 
or buy some extra
tubing?" the answer should be obvious!

Have fun!

George de Piro  (Nyack, NY)


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Date: Sat, 29 Aug 1998 08:00:55 -0700 (PDT)
From: Domenick Venezia <demonick at zgi.com>
Subject: Stirring starters

Riedel, Dave" <RiedelD at PAC.DFO-MPO.GC.CA> asks:

>> In HBD #2807, Hugh Hoover asked:
>> Stir plates.  There are repeated assertions that they increase
>> the available O2, which increases the health & growth of the yeast.
>> Ok, but riddle me this... After fermentation starts, and a CO2
>> blanket covers the yeast, how does the stirring improve oxygenation?
>> ...
> So far as I've noticed, no-one responded.  I'd like to know what the
> consensus is on this, as I like the idea of the stir-plate as a cost
> effective and simple alternative to direct oxygenation of starters. Does
> the agitation encourage yeast growth?  By stirring the wort, you
> should create enough disturbance in the vessel to disrupt the C02
> blanket, but I would think this only applies until the point at which
> the C02 has forced all of the air out of the fermenter.

As the fermentation vessel (flask) is unsealed, but plugged with cotton or
filter, simple diffusion would help to keep some O2 in the flask. Stirring
also disrupts the CO2 blanket and increases the rate of O2 diffusion into
the flask.  The agitation also keeps all the yeast cells suspended and in
contact with all the nutrients in the media.  Without agitation local
nutrient voids can be created in the media by particularly active cells.
These could be voids of any rate limiting nutrient. Natural diffusion
would tend to fill these voids slowly, but if the active cells are
metabolizing faster than diffusion can replenish the supply the void would
remain.  "Starved" cells flocculate, so some cells may drop out of
solution (the best and brightest) prematurely in response to purely local
conditions.  By stirring, these cells are always presented with what they
need and can continue to grow swiftly until all the nutrient(s) in the
entire flask are consumed.  I would think that in this way stirring helps
select for the most active yeast cells. 

Domenick Venezia   demonick at zgi dot com



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Date: Sun, 30 Aug 1998 13:13:42 -0500
From: "charles beaver" <cbeav at netnitco.net>
Subject: Oatmeal Stout

I am contemplating making an oatmeal stout in the next few weeks. As a
veteran single step infusion masher I and wondering if it is a *mandatory*
that I include a protein rest. Any opinions are welcome.

Thx




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Date: Sun, 30 Aug 1998 14:44:29 -0400
From: Denis Barsalo <denisb at cam.org>
Subject: Hop growing question

Hoppers,

	Given two vines of equal size, which one would grow larger, fatter
cones? Cascade or Perle?

Denis Barsalo




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Date: Mon, 31 Aug 1998 13:07:22 +11:00
From: "Darren Robey" <robeyd at vida.agvic.gov.au>
Subject: glass carboy

Dear brewfolk.

I have ben given a 5 gal galss carboy, but there is 1 problem. It has 
a round outles in the bottom.  What sort of bung would I use to stop 
this that wouldnt taint the beer. would ruber or cork etc be useful?


Cheers

Darren


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