Every step of transforming green coffee into hot brewed coffee makes the flavor essence of the bean more vulnerable to destruction. Green coffees keep for years, roasted coffees begin to lose flavor after a week, ground coffee an hour after grinding, and brewed coffee in minutes.
Once roasted, coffee beans still keep fairly well. But once the coffee is ground, it begins to go stale in a few hours. Canning or otherwise packaging ground coffee simply replaces the natural coffee package, the bean, with an inefficient artificial package. When consumers break open the artificial package, they may find a coffee that is relatively fresh, but not for long.
The easiest and most effective way to assure freshness is grind your coffee yourself just before you brew it. Grinding coffee fresh just before you brew it is one of the easiest things that you can do to improve the quality of your coffee.
Buying Coffee Fresh and Keeping It That Way
The ideal coffee routine would be as follows: Buy the coffee in bulk as whole beans. Put the beans in an airtight container in a cool, dark place, and take out only as much as you want to grind and brew immediately.
A good way to store whole bean coffee is in an airtight solid glass jar with a rubber gasket inside the cap that gives a good seal. Don't put the beans in the refrigerator. The moisture and smells will destroy the freshness and flavor. Freezing whole beans works well, but only light to darkish brown roasts. Very dark-roast coffees do not freeze well.
If you order coffee by mail and you know about how much coffee you consume each month, you can put in a standing order with a coffee roaster, so your coffee comes fresh every other week, a couple of pounds at a time.
Grinding Your Own
How Fine the Grind
In general, grind coffee as fine as you can without clogging the holes of the brewer or turning the coffee to mud. The finer the grind, the more contact there will be between coffee and hot water, and the faster and more thoroughly the essential oils will be released, without activating harsher, less-soluble chemicals.
On the other hand, you don't want to grind your coffee to a powder, because completely pulverizing it destroys the essential oil, which becomes vaporized by the heat and friction of the grinding process.