Actually, it's not the O2 molecules left behind - if
you're pulling a vacuum there is nothing left but
negative pressure with respect to the gas pressure
within the beans. While it is true that some O2 will
be left behind, after pulling a vacuum it is miniscule
compared to the volume of CO2 that will result from
outgassing. It's the volume of that negative pressure
that determines how LONG the pressure differential
exists between the beans and the evacuated void in the
In a perfectly sealed RIGID container with a vacuum
drawn on it and an outgassing material inside of it,
and a gauge reading the vacuum, you would observe over
time that the vacuum reading in a few hours or days
would not be the same as when you left it.
This is because the gas (in the beans' case, CO2) is
leaving the interior of the beans in an attempt to
equalize the pressure between them and the voided
container. Smaller volume containers will reach this
equalization sooner than larger ones thereby reducing
the rate of flow of the outgassing of the beans.
It's an exponential relationship - as the beans outgas
into the vacuumed space, the pressure differential
decreases, decreasing the rate of degassing or
outgassing material. It stands then that the smaller
evacuated volume will continue degassing at a slower
rate than the larger one.
You don't want to degas completely because as already
discussed, once the protective envelope of CO2 is gone
the game is over.
You'd be better off as someone suggested to fill the
remaining volume with something inert if you weren't
going to fill it with beans. Glass is one of the
lowest outgassing materials to fill such volume - I
haven't seen the effects of glass outgassing until you
start pulling down to 0.1 micron (which is what we
called perfect vacuum, from a scientific standpoint).
You won't even come close with a foodsaver.
My suggestion is to fill the bottom of the canister
with marbles, put a metal divider that comes very
close to the sidewalls of the canister, and then pour
your beans on top of that. The easier route is to use
a smaller canister if possible.
number of O2
obxwindsurfhttp://www.virtualfusion.com"The real voyage of discovery consists not in seeking new landscapes but in having new eyes -- Marcel Proust"
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