Unky Phil's Oxygen Experiment

<editor's note>
 - a post from the HBD
</editor's note>

Date: Thu, 5 Sep 2002 08:38:11 -0400
From: "Philip J Wilcox" 
Subject: Disolved Oxygen Research

Hi all,

Since the HBD has been a bit anemic while we are getting used to our new
fall schedules, I thought I would pass along some research my uncle (Phil
DeVore) the winemaker has been working on. Phil is not a regular HBD reader
so if you could CC: him at ped@qtm.net with any commetary, we would be much
abliged.

Phil Wilcox
Poison Frog Home Brewer
Warden-Prison City Brewers
In Jackson, MI 32 Mi. West of Jeff Renner
AABG, AHA, BJCP, HBD, MCAB, ETC., ad nausium...
See our languishing and outdated website at http://hbd.org/prisoner

Dear Friends:


I want to bring you up to date on my research on dissolved oxygen in water,
as a proxy for dissolved oxygen in musts.  First, I must admit that what I
have done is very primitive.  But it is a start.


This research required two things.  First, a good dissolved oxygen meter is
required.  I recently purchased an YSI 550. This was apparently a
fortuitous purchase, as my account representative with Fisher Scientific
told me after the fact that this is one of their best selling items.  The
second is a way to oxygenate water.  I purchased a 30 gallon/hour aquarium
pump, used with a dispersion stone that Phil was kind enough to provide.


As a starter, what is the dissolved oxygen of water?  The meter showed that
tap water has 10.06 mg/L of oxygen (10 ppm).  This is essentially the
saturation level of water. The next step was to deplete the water of oxygen
so its addition into the water could be monitored.  I ran 6 volumes of
nitrogen through the water, reducing the oxygen level to 0.08 ppm.  This is
close enough to 0 so I saw no need to sparge more nitrogen.


The next question is how much air the pump and dispersion stone really add,
considering my stone and the 9' of plastic tubing.  I filled a 3 gallon
carboy with water and placed it is a tub partially fill of water.  It took
12 minutes 50 seconds to displace all the water, so the rate was 4 minutes
15 seconds to displace a gallon.  This is just under half what the pump was
rated at, but so what, at least I know what my unit does.


The next step was to use the pump and stone to aerate the water and measure
the results.  I used a 5 gallon carboy for best accuracy but for
convenience have adjusted everything to a 1 gallon basis. Remember that for
my situation 1 gallon of air (0.21 gallon of oxygen) is sparged is 4
minutes 15 seconds.  My results are shown below:


Volumes of Air/Volume of Water      Dissolved Oxygen (ppm)


0.00                                                0.14


0.063                                              0.89


0.125                                              1.66


0.25                                                3.00


0.50                                                4.90


1.00                                                7.25


2.00                                                8.64


4.00                                                9.00


8.00                                                8.80


These results show several things.  First, the rate at which oxygen is
absorbed into the water rapidly decreases.  This is no doubt due to the
fact that the more oxygen in the water, the more that is scrubbed out by
the nitrogen.  One gas displaces another, and since nitrogen is
volumetrically superior, this limits the oxygen that may be absorbed.  It
is also shown that the concentration of oxygen is never as great as occurs
in nature, but it is a very stout 90%.  As air (and oxygen) is absorbed
under normal conditions, there is no violent nitrogen scrubbing as we have
here, so oxygen ends up at somewhat greater levels.


The real question is what this all means, and what practical guidance may
be gleamed.  My inclination is to turn over 1 volume of air, which will
result in about 7.2 pm of oxygen addition.  This does not include any
oxygen the yeast might metabolize during the time of sparging.  I am
guessing that this is relatively small.  If one wants more oxygen addition,
I think the best bet is to wait till the oxygen drops to below 1 ppm and
then go through the same process all over again.


For my setup, this would call for sparging about 4 minutes for every gallon
of must.


It should be noted that a very small percentage of the oxygen sparged into
the water is absorbed.  This is due to the slow rate of oxygen absorption
and increasingly the sparging action of nitrogen as the oxygen level
builds.  Prior calculations have shown that one turn of air contains enough
oxygen to add 251 ppm to a gallon of must.  Clearly only a small amount of
the potential oxygen is absorbed.  Perhaps this is due to the grace of the
wine gods.  If must/wine absorbed oxygen at a more rapid rate, we would be
making vinegar, not wine!


Any thoughts you might have would be well appreciated.


Best regards,


Phil  DeVore


ped@qtm.net

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