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HOMEBREW Digest #5204
HOMEBREW Digest #5204 Tue 10 July 2007
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
Re: pH of bleach solution affecting santizing effect ("Craig S. Cottingham")
Re: Wheat Beer Yeast survey (Robert Tower)
Bleach ("A.J deLange")
Our price: $149 Retail Price - $1199 Adobe Suite 2 ("Avery Saenz")
Wheat yeast (Thomas Rohner)
bleach and vinegar solution ("Jason Bryant")
bleach and pH (mabrooks)
Re: sanitisers ("steve.alexander")
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Date: Mon, 9 Jul 2007 23:58:47 -0500
From: "Craig S. Cottingham" <craig.cottingham at gmail.com>
Subject: Re: pH of bleach solution affecting santizing effect
On Jul 9, 2007, at 09:09, Bill Velek <billvelek at alltel.net> wrote:
> I'm curious because I've
> read over and over again about using bleach solutions to sanitize, not
> only in myriad threads all over the Internet, but also in many brewing
> books, and _NEVER_ has it ever been suggested, IIRC, that something
> should be added to lower it's pH (vinegar was suggested on r.c.b.).
>
> What are the pros and cons of using an equal mix of vinegar and
> bleach?
> And can it be used as a 'no-rinse' sanitizer?
It's been too many years since I had a chemistry class, so I had to
resort to Google:
<http://www.eurekalert.org/pub_releases/2006-02/asfm-vik021306.php>
Vinegar increases killing power of bleach
Adding white vinegar to diluted household bleach greatly increases
the disinfecting power of the solution, making it strong enough to
kill even bacterial spores. Researchers from MicroChem Lab, Inc. in
Euless, Texas, report their findings today at the 2006 ASM Biodefense
Research Meeting.
Sodium hypochlorite (NaOCl) in the form of laundry bleach is
available in most households. The concentrate is about 5.25 to 6
percent NaOCl, and the pH value is about 12. Sodium hypochlorite is
stable for many months at this high alkaline pH value.
"Laundry bleach is commonly diluted about 10 to 25-fold with tap
water to about 2000 to 5000 parts per million of free available
chlorine for use as an environmental surface disinfectant, without
regard to the pH value of the diluted bleach. However, the pH value
is very important for the antimicrobial effectiveness of bleach,"
says Norman Miner, a researcher on the study.
At alkaline pH values of about 8.5 or higher, more than 90 percent of
the bleach is in the form of the chlorite ion (OCl-), which is
relatively ineffective antimicrobially. At acidic pH values of about
6.8 or lower, more than 80 percent of the bleach is in the form of
hypochlorite (HOCl). HOCl is about 80 to 200 times more antimicrobial
than OCl-.
"Bleach is a much more effective antimicrobial chemical at an acidic
pH value than at the alkaline Ph value at which bleach is
manufactured and stored. A small amount of household vinegar is
sufficient to lower the pH of bleach to an acidic range," says Miner.
Miner and his colleagues compared the ability of alkaline (pH 11) and
acidified (pH 6) bleach dilutions to disinfect surfaces contaminated
with dried bacterial spores, considered the most resistant to
disinfectants of all microbes. The alkaline dilution was practically
ineffective, killing all of the spores on only 2.5 percent of the
surfaces after 20 minutes. During the same time period the acidified
solution killed all of the spores on all of the surfaces.
"Diluted bleach at an alkaline pH is a relatively poor disinfectant,
but acidified diluted bleach will virtually kill anything in 10 to 20
minutes," says Miner. "In the event of an emergency involving
Bacillus anthracis spores contaminating such environmental surfaces
as counter tops, desk and table tops, and floors, for example,
virtually every household has a sporicidal sterilant available in the
form of diluted, acidified bleach."
Miner recommends first diluting one cup of household bleach in one
gallon of water and then adding one cup of white vinegar.
- --
Craig S. Cottingham
craig.cottingham at gmail.com
------------------------------
Date: Mon, 09 Jul 2007 22:44:50 -0700
From: Robert Tower <roberttower at sbcglobal.net>
Subject: Re: Wheat Beer Yeast survey
Richard Lynch asks what hefeweizen yeasts we all like to use. First, I
tend to like White Labs WLP380. That being said, I think to a certain
extent the strain is less important than how you treat it. Most
hefeweizen strains are extremely sensitive to temperature, pitching
amount, and oxygen levels. I've gotten wildly different beers using the
same strain and recipe but by varying those three factors. I've settled
on a pitching amount, but I've still yet to arrive at the optimum
temperature (although I'm getting close) and I'm not even in the ball
park when it come to the ideal oxygen level. Further research is
necessary! :-)
I've used White Labs WLP300 but found that it's too easy (for me at
least) for the banana character to get excessive. I've also tried Wyeast
3068 (Weihenstephan) but found that it didn't have enough banana
character. However, both of these problems may be the result of improper
management of the three aforementioned factors. I chose WLP380 simply
because it is described as a yeast that emphasizes phenolic/clove notes
and has a muted banana character which is how I like my hefeweizens. I
figured that I would pick the yeast that closest matched my theoretical
ideal and then I would fiddle with the yeast ranching conditions until I
got it just right.
It's very tricky I'm finding. Last year, I made a hefeweizen, fermented
at 66 F. It took first place in class and best of show runner up at a
local annual competition. But all the judges did criticize it for being
too fruity and recommended a lower fermentation temperature. This year I
brewed it exactly the same for the same competition but lowered the
temperature to 62 F. and it received lower scores overall and didn't
even place. Maybe the actual relationship between temperature, pitching
rate and oxygen is important and by lowering the temperature the other
two factors are now out of whack. My plan for the next batch is to bring
the temperature back up to 66 F. and increase the oxygenation over last
year's version. If that doesn't yield satisfactory results then I will
increase the pitching rate to keep the fruitiness in check. Ah, the
quest continues!
Bob Tower / Los Angeles, CA
------------------------------
Date: Tue, 10 Jul 2007 11:04:50 +0000
From: "A.J deLange" <ajdel at cox.net>
Subject: Bleach
It is true that bleach is more effective at low pH than high because the
HOCl molecule is smaller than the OCl- ion and is thus better able to
slip through the cell wall/membrane of the target organism and effect
kill. For example CxT (the product of the concentration time time
required for 99% kill of E. coli) is about 100 times less for HOCl than
for OCl-. The lower the pH the greater the proportion of HOCl in a
solution. At the high pH of bleach (which can be made by bubbling
chlorine gas through a lye solution - hence the high pH which is good
for the product's stability - up to a point) nearly all the chlorine is
OCl-. At pH 7, by comparison, about 72% of it is HOCl, at pH 6 96.5% is
HOCl at at pH 5 99% so yes, lowering the pH is effective. The problem
(and you knew there had to be a problem) is that if you go to far (below
about 4) the HOCl decomposes releasing chlorine gas which is obviously a
potential safety hazzard. So if you are sure you can control the pH you
can increase the effectiveness of hypochorite bleach but be careful. I'm
not sure I'd want to use vinegar as the acid for anything that would
touch beer as vinegar is awfully persistent.
A.J.
------------------------------
Date: Tue, 10 Jul 2007 11:14:41 -0900
From: "Avery Saenz" <papower at thewizardscastle.com>
Subject: Our price: $149 Retail Price - $1199 Adobe Suite 2
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------------------------------
Date: Tue, 10 Jul 2007 13:26:54 +0200
From: Thomas Rohner <t.rohner at bluewin.ch>
Subject: Wheat yeast
Hi Richard
after testing different yeasts, we found that Wyeast 3068 gives the most
typical clovey and banana aromas. The fermentation temperature has a
large influence as well. We ferment it from 20-22 deg. celsius. We brew
from 3 to 6 50 litre batches a year. Helles Weizen, dunkles Weizen,
Weizenbock and a raspberry wheat. We hop them with german noble hops
like Tettnanger or Hallertauer. For the last helle we had a funny idea.
How would it taste with a late addition (5 min) of Cascade hops? So we
tried it and it tastes great. We will certainly do this again.
Cheers Thomas
------------------------------
Date: Tue, 10 Jul 2007 08:14:15 -0400
From: "Jason Bryant" <smokeykhan at gmail.com>
Subject: bleach and vinegar solution
Basic Brewing radio had a podcast on this topic on March 29th.
http://media.libsyn.com/media/basicbrewing/bbr03-29-07.mp3
James Spencer, the host, interviewed Charlie Talley from Five Star
Chemicals (maker of Star-San). Charlie spent a lot of time talking
about using bleach as a sanitizer. One of the things he talks about
is how effective a bleach and vinegar solution is. The one thing that
he was sure to stress was that you need to dilute the bleach in
water before adding the vinegar (or was it the other way around?).
The point being, do not mix bleach and vinegar directly. Duh.
Also, if you are interested, check out the podcast from the week before.
http://media.libsyn.com/media/basicbrewing/bbr03-22-07.mp3
James interviews the guy from National Chemicals who makes
iodophor. Learning how the stuff works directly from the horse's
mouth made me change the way I use iodophor and has saved me a
bunch of time (and sanitizer) during brewing and bottling.
If those links don't work just go to basicbrewing.com and click on
Podcasts > Basic Brewing Radio, then scroll down to the one you want.
Jason
Norfolk, VA
------------------------------
Date: Tue, 10 Jul 2007 09:45:12 -0400
From: mabrooks at vt.edu
Subject: bleach and pH
In a recent post:
>Date: Mon, 09 Jul 2007 09:09:36 -0500
From: Bill Velek <billvelek at alltel.net>
Subject: pH of bleach solution affecting santizing effect
>Most people don't understand that just putting bleach into water
makes a very alkaline solution which has nil sanitizing power
compared to lowering the pH to 7 or so, which is then very
powerful. Microbe lifetimes of milliseconds versus minutes."
First off - PLEASE DO NOT MIX STRAIGHT BLEACH WITH ANY TYPE OF ACID!
CHLORINE GAS CAN FORM AND FOR OBVIOUS REASONS IT IS UNDESIRABLE!
The pH of a bleach solution will depend on the ratio of "bleach to water"
and the buffer capacity of the water you added the bleach to. Typical household
Chlorox is indeed a highly buffered solution, however, it also has a
concentration of
5.25%, which equates to 52,500 mg/l, hence you dont need to add much to water to
get the germicidal effectiveness you desire, which is really only about 5 mg/L,
for 10-15 minutes or so depending on temperature. To get that type of dilution
you would not need much bleach in 5 gallons of water and if the dilution water
was at or anywhere near a neutral pH of 7, the highly buffered bleach would be
brought down to the pH of the water very quickly. As far as HOCl and germicidal
effectiveness is concerned, it is true that the higher the pH of the bleach
solution,
the less HOCl there will be and correspondingly the less the germicidal
effectivelness
will be, the OCl- ion is a relatively poor disinfectant. One would need a very
highly buffered solution (> pH 8.0) in order to reduce the germicdal
effectiveness
of bleach to the point that it is useless, this is highly unlikely with the
dilutions in a normal tap water. The ratios of HOCl vs. OCl- at various pH's can
be
found with ease on the internet via a google search, of course there are other
factors to be considered, however, they likely dont come into play for
homebrewing
purposes, ie. TDS of the solution etc....
In short, it is not recommended to use bleach undiluted, as the concentration is
much more then necessary for any disinfectant needs and will likely be useless
as
the pH is much too high and is mostly in the OCl ion form, hence, not very
effective.
It is better to make a solution of bleach and water at about 5 mg/L, perhaps a
little
less if you want to go with a no rinse technique. and please dont mix bleach
with any
type of acid!
Much more can be said/presented on this topic if there is interest by the
masses.
Matt B.
Northern VA.
------------------------------
Date: Tue, 10 Jul 2007 13:35:38 -0400
From: "steve.alexander" <-s at adelphia.net>
Subject: Re: sanitisers
Bill Velek notes ...
> Subject: pH of bleach solution affecting santizing effect
>
> In a recent post on the r.c.b. usenet group, a poster stated that:
> "Most people don't understand that just putting bleach into water
> makes a very alkaline solution which has nil sanitizing power
> compared to lowering the pH to 7 or so, which is then very
> powerful. Microbe lifetimes of milliseconds versus minutes."
>
Mostly correct, tho' a bit misleading.
Most common brew/wine sanitizers (iodophor, meta-bisulfite salts,
hypoclorite
salts (aka bleach)) depend on the equilibrium of toxic specie with less
toxic specie.
There is a pH based equilibrium between the less toxic and more stable
species at high pH and the less stable and more toxic specie at low pH
(acidic
conditions).
I think every winemaker and most brewers are familiar with the charts
that show
the effectiveness for campden tablets vs pH. In that case campden tab
(0.44gm of
potassium metabisulfite or ~2mMoles as I recall), produce ~4mMoles of total
SO2 specie with this equilibrium at low pH.
SO2 + H2O = HSO3- + H+
Here a lower pH favors the left hand side with free, toxic SO2. At pH 3.0
about 6% of the total SOx appears as free, toxic SO2, while at pH=4.0
it's only
0.6%. At pH 4.0 you either need to lower pH by 1 or add 10x as much sulfite
to achieve the same "sanitizing power".
Similarly for bleach; Common household bleach is a 5.25% solution of
sodium hypochlorite. There is a equilibrium at very low pH as:
Cl2 + H2O = HOCl + H+ + Cl -
which releases free Cl2 gas as pH drops and at intermediate pH as:
HOCl + OH - = OCl- + H+ + OH-
Both eqn drive to the left as pH decreases. The point is that the
hypochlorous acid
(HOCL) is a toxic agent but at very low pH it's converted to chlorine
which is not
very soluble so evolves as chlorine gas which is more toxic to the
brewer than the
bacteria.
I don't have the equilibrium constants, but graphs indicate that at pH
8, about 10%
of the chlorine appears as HOCl, almost 100% at pH=5 and only 10% at pH=0.7
(roughly). We do NOT want to drive the pH below 5.0 since then we are
converting useful HOCl to dangerous Cl2 gas. But it's true that above
pH 8
the effectiveness drops off - depending on the concentrations. At pH 9 only
5% of the chlorine is in the toxic species, 10% at pH=8; at pH 7 it's
about 80%.
So yeah - ideally your bleach solution should have a pH between 5 and
7, but
bleach is inherently basic so acidification of a bleach solution is a
very good idea.
Vinegar is a reasonable way to acidify, but you'd need a meter (strips
won't work
in bleach) or maybe a swimming pool pH kit to test since water hardness and
other buffering will be a major factor.
Blind mixing is not ideal ! Note tho' that 1 fl.oz of 5.25% sodium
hypochlorite sol'n (household bleach) has about 20mMoles of OCl- and this
can be 'toxified' to HOCl with the addition of 20mMoles of hydronium or
about
the amount present in 0.81 fl.oz of 5% acetic acids solution (household
vinegar).
Given the fact that most waters have a bit of carbonate hardness
buffering to
overcome a 1:1 ratio of bleach to vinegar seems reasonable. *DO* *NOT*
add bleach to vinegar or any acid directly, instead add the bleach to
water and
mix then add vinegar or other acid slowly while mixing.
> What are the pros and cons of using an equal mix of vinegar and bleach?
> And can it be used as a 'no-rinse' sanitizer?
>
There is one HUGE "con" to adding acid to household bleach. This drives the
equilibrium hard to the free Cl side of the eqn and Cl is not very
soluble in
water so it produces chlorine gas. 1000ppm of chlorine gas is a fatal
concentration and at lesser concentrations it burns lung tissue and can do
considerable damage rapidly. If you really feel the necessity to add
acids,
then do so with proper regard for the very real dangers and not below pH 5.
I do not believe that any of these procedures make this a "no rinse" type
sanitizer. Food industry regs suggest no less than 200ppm of total
chlorine to
a max of 2000ppm (0.5 fl.oz to 5 fl.oz of household bleach per gallon) at pH
of 6.5-7.5. Obviously you need less at lower pH. I don't think the
residual
chlorine would be acceptable as it can produce some very potent
chloro-phenolic compounds which have no acceptable level in beer.
-S
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End of HOMEBREW Digest #5204, 07/10/07
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