I found this tidbit in the Jacksonville.com web site. Thought it was worth sharing.
The enemy of fresh roasted coffee is oxygen, and as long as the coffee is desorbing CO2, oxygen cannot be absorbed. At approximately 10 days, coffee is completely degassed of CO2 and the coffee is beginning to stale. This process is similar to the yeast in bread. Once the yeast in bread degasses, the bread is stale and stiff. If only coffee would go stiff like bread, we would then have an obvious indicator of whether the coffee is stale or not.
How can you tell if coffee is stale? Once you open the bag, can, brick, pod or super-infused nitrogen hypersensitive krypton pouch and the last gasp of freshness escapes into the atmosphere, the coffee has the aroma of cocoa in a matter of hours. Not a sweet chocolate smell, but an odor of cocoa. If you brew stale coffee it has a bitter taste. Of course if you load your coffee with cream and sugar, salt and eggshells, you will never taste the stale coffee.
To hide the stale coffee taste and to give the public a consistent sameness of taste and aroma, one of the tricks of the trade is to flavor the stale coffee with a coffee flavor. This is synonymous with coating week-old fish with a fresh-caught flavoring.
This is very popular in push-button coffee operations and a few national chains.
Coffee, if roasted correctly, has a mellow, sweet taste.
A single coffee bean should yield a spark of the caramelized sugars on the tip of your tongue. The portion of the roasted coffee to test this is the kernel within the husk of the coffee.
Don’t miss the third paragraph above, it’s a beauty!