Degassing/Storage

Roasted beans give off carbon dioxide over
a period of weeks, but approximately 40% is given off in the
first 24 hours. If the beans are ground and brewed drunk
immediately then some of this CO2 would dissolve in the water
and give a true acid taste. A French press of freshly roasted
beans will froth alarmingly – stale beans will hardly froth at
all. In addition, the flavors on some beans seem to develop over
a period of 2 to 3 days. Thus beans should be left to degas for
a day or two. It is not essential. Fresh coffee is not bad
immediately. The beans just improve.

Staleness is mostly caused by oxygen getting to the bean (also
partly by internal chemical changes.) Probably the best method
is to put them in a one-way valve bags. They let the CO2 out but
prevent the oxygen coming in. A lot of home roasters use Mason
jars (glass bottling jars).

At any point in time you might choose to have 3 or 4 little jars
on your kitchen side. Perhaps a light Colombian for all day; a
gutsy Java to wake me up; a light espresso blend for straight
shots and then perhaps a heavy cappucccino blend comprising
Indonesians and robusta for cutting through the milk. None of
them will be around for more than a week or so so they will stay
fresh. The average commercial roaster might just have got his
roasted beans to the shop or the warehouse in the first week.

As a side note I will say that due to the quickness of
consumption of home roasted coffee storage is less of an issue
than for people who want to keep their coffee for an extended
time.

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