Great coffee starts with fresh beans.
If you’re looking for the freshest coffee you can get, you should purchase coffee from a coffee roaster. Look for a roasted on date written on the bag or on a sticker. This indicates the day in which the beans were roasted so you know about how fresh they are. Anything more than about 2 weeks from the roasted on date should generally be avoided.
Store the beans in an air tight container, such as a Friis Coffee Vault which has vent filters to allow CO2 to escape and prevent O2 from getting in. Keep the container in a cool dry area like a cabinet in your kitchen, but not in a freezer or refrigerator.
Grind coffee just before you brew. Coffee ground in the store or factory creates more surface area, releasing the carbon dioxide faster, thus the coffee will become stale faster.
Also never reuse your coffee grounds to make coffee. Once brewed, the desirable coffee flavors have been extracted and only the bitter ones are left.
As a part of the roasting process, gases develop inside the structure of the coffee bean. Upon exiting the roaster, these gases, CO2 chief among them, begin escaping the bean: “off gassing,” as it’s called. When coffee is still very fresh (say, one or two days old), the carbon dioxide off gassing that’s occurring is so rapid and volatile that it adversely affects coffee brewing.
If your coffee is fresh, you’ll experience more off gassing. If you experience more off gassing, your coffee’s extraction (a measurement of how much mass is removed from dry coffee grounds by water–basically, “how well you brewed the coffee”) will be uneven and unpredictable.
As carbon dioxide makes its effort to escape the bean, oxygen attempts to make its way in. This process, called oxidation, leads to coffee’s staling, and the general decline of its flavor. This is why I use the Friis Coffee Vault containers. 7-12 days after roasting the carbon dioxide off gassing that inhibits proper extraction has calmed down, while the staling effects of oxidation have not begun to settle in. This timetable is not hard-and-fast but is a general guideline to go by.
Why NOT to buy pre-ground coffee.
Coffee oils are very delicate, which makes them an easy victim of contamination. Whatever odors are around ground coffee will taint it in ways that will not contribute to your coffee tasting experience.
Oxygen: The cells inside the roasted coffee bean contain many different volatile aromas and flavors. Once ground the volatile aromas are immediately released and they react with oxygen in the air (oxidation). After 15 minutes the ground coffee loses about 60% of its aroma.
Moisture: Coffee oils are water-soluble. That’s a good thing or it would be very difficult trying to get the oils out of the bean. This fact however poses a great problem for ground coffee. When ground coffee is exposed to moisture in the environment it immediately starts to dilute the oils.
Carbon Dioxide Depletion: Increased surface area permits for greater carbon dioxide off gassing. During the roasting process a lot of CO2 is created. Since the bean is porous, some of it is lost during the cooling process. Much of it, however, is retained within the cells of the coffee bean. This CO2 plays an important role in that it is the primary method for getting the essential coffee oils into the coffee once they are released. The problem is that the increased surface area created after grinding permits for greater CO2 off gassing.
The Solution: always grind your coffee freshly just before brewing. Just imagine how much flavor, aroma is gone and how much staleness is present in pre-ground coffee from a factory that has been waiting to be shipped, been in transit and then placed on a store shelf for who knows how long.
I was simply stunned at how much better tasting coffee was when I first started grinding my own beans at home and brewing them immediately.
I hope this information is helpful to anyone looking for the best cup of coffee they can get.