[Homeroast] Storage right after roasting

John Nordling john.nordling at gmail.com
Tue Aug 19 11:22:39 CDT 2014


I mostly agree with you, but given that CO2 is more dense than O2
(considerably), left undisturbed,  by and large, you shouldn't get much O2
down on your beans (assuming a small opening, no breeze, etc.)

Now, given that I open mine up every day to take a few scoops for grinding,
I get O2 in there.  I solve the problem mostly by drinking a lot of coffee.

-John



~~
"Can't believe how strange it is to be anything at all."   Neutral Milk
Hotel, *In the Aeroplane Over the Sea*

Email:  john.nordling at gmail.com


On Sat, Aug 16, 2014 at 1:46 PM, Michael Koenig <koenig.mike at icloud.com>
wrote:

> I've ranted on this topic in the past before, so hopefully the old timers
> on the list will bear with me.
>
> Gases are funny things and mix very readily. It's easy it assume they
> behave like oil and water, but the reality is they they mix readily.
> Therefore the CO2 given off by the resting beans will ALWAYS be mixed with
> O2.  You may reduce the concentration of O2 but it's my contention that in
> order to exclude meaningful amounts of O2 you need to either pull a vacuum
> on your container (pulling your volatiles out with it), or extensively
> purge with another gas.  On the timescale we drink our coffee it simply is
> not worth jumping through these hoops.  (Nitrogen flushed bags might be
> worthwhile for a commercial roasting operation who wants longer shelf-life).
>
> Back in my lab days we had a glovebox that was flushed with nitrogen to
> work with oxygen sensitive compounds. It required several pump downs and
> nitrogen flushes to get out all the oxygen. This is something that's just
> not practical or worth worrying about for us home roasters.
>
> --mike
>
> Sent from my iPhone
>
> > On Aug 16, 2014, at 1:31 PM, Mike Davis <mldavis2 at sbcglobal.net> wrote:
> >
> > I think the big unknown in storage techniques is the effect of oxygen
> (if any) to the resting process.  Over a long enough time period, coffee
> will go stale of course when exposed to oxygen.  But on the other side, we
> know that "resting" can enhance the flavor. So the real question would seem
> to be what happens during the "resting" time and if the presence or absence
> of oxygen is responsible for the improvement.  Logically, if CO2 is a
> result of chemical process taking place during "resting" then oxygen should
> be nearly non-existent.  It is possible that cooling could pull oxygen back
> into the beans.  But storage immediately after cooling would seal them from
> additional oxygen as the beans exuded CO2 which would expel oxygen from the
> container for a while before oxygen begins to work its way back in when CO2
> pressure is reduced to equal.  So I assume (perhaps incorrectly) that the
> favorable chemical processes that enhance coffee during resting are a
> "coasting effect" of heating and continue to completion in the (nearly)
> total absence of oxygen.  In other words, they are not an oxidation process
> as such requiring oxygen.
> >
> > So my system (such as it is) is based on those assumptions.  Put the
> beans into a light-tight container (AirScape canister) with minimal holes
> just sufficient to allow exit of CO2 overnight, yet so small that the
> greater CO2 pressure probably prevents incursion of oxygen as the CO2
> exits.  Then seal the canister once the CO2 has stopped. There should be
> little or no oxygen present except what little might remain in the beans,
> and the coffee should complete the chemical "coast" and then more or less
> stop, waiting for the lid to be unsealed.  I think this is the idea behind
> coffee that is weeks old (or older) on store shelves - one way CO2 valves
> that exclude oxygen.  Once my beans are loaded into the hopper, then of
> course, there is abundant oxygen and staling begins.
> >
> > That's just what seems to work for me.  I'm always open to better
> suggestions and ideas.
> >
> > Mike Davis
> >
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