The best way to tell if it has gone bad is to use your sense of smell. If coffee has gone bad, the pleasant aroma will be gone and with it much of the taste. Using this coffee will not harm you, but will just not have much flavor if the smell is gone. It may also lose its deep dark color and appear a lighter brown.

Coffee does degrade over time and it degrades faster depending on the surface area - which means that the whole beans will keep longer than ground coffee. The best way to store these beans is to place them in an air-tight container in the freezer. You should grind fresh only the amount you plan to use that day to avoid unnecessary exposure. Storing coffee in this way will keep out moisture and other contaminants.

The best way to store ground coffee to keep it fresh longer is by storing it in your freezer immediately after use. Storing coffee in the freezer does not freeze the coffee, so it is always ready for use without any defrosting.