[Homeroast] Using CO2 to preserve freshness?

Mike Koenig koenig.mike at gmail.com
Fri Apr 16 08:56:57 CDT 2010


Don't bother with the CO2 duster..  If you want to purge all the oxygen out
of a mason jar, you will need a LOT of purging, and will probably require
the entire volume of your duster (or more).  The only way to totally exclude
oxygen is to pull a high vacuum on the jar, and then fill it with your
desired gas (even this will take several purge and fill cycles to remove all

I know I've ranted on this topic before (so apologies to the list if you are
sick of it), but gases are funny things, and because we generally can't see
them, it's hard to visualize their behavior.  They don't behave the way
liquids do.  Two gases will rapidly mix together (even if one is heavier
than the other).  You will never get the "oil and water" situation by mixing
two gases in a container,  and even if you have a jar COMPLETELY purged of
oxygen (which is impossible without a vacuum pump), the first time you open
it, no matter how careful you are, you WILL introduce oxygen.  The effort to
maintain a low-oxygen environment for storing coffee would far exceed the
efforts we expend roasting, for little benefit. (in my not-so-humble

If you don't believe my logic, then consider that if it were not true, you
would not be alive, because all the heavier gases in the atmosphere would
collect at ground level (CO2, Argon, etc, and the oxygen would go up to
higher altitudes.

Bottom line--drink your coffee within two weeks, and don't worry about it.

(I also have a theory that oxygen is a necessary part of the "resting"
process, and that staling and resting are just the progression of similar
reactions,  but I've never wanted to waste coffee trying this out. If anyone
has done any experiments comparing coffee rested in a nearly oxygen free
environment, with coffee rested the normal way, I'd be curious)


On Wed, Apr 14, 2010 at 1:38 PM, Dan <d54696 at yahoo.com> wrote:

> I have a small CO2 duster (for photographic use) which I was going to use
> for blowing out my grinder. However, for the grinder, I found a bulb type
> blower that works much better.
> I've been adding a squirt of CO2 to my Mason jars of roasted beans, but I
> really don't know if that is of any help in slowing staling. Does anyone
> have any experience/proof that this is beneficial or a waste of time? I do
> know when making wine we use a large CO2 tank to 'top' off the fermenting
> grapes and that is supposed to be beneficial.
> I do think that when removing the beans, if one pours them, the CO2 will
> spill out. Maybe I'll put a match in a jar and see if it is extinguished or
> perhaps a canary.
> Thanks
> dan

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