CO2 AND OXIDATION
Generally speaking, fresh coffee is better than old coffee – but that's only part of the truth. After roasting, coffee contains a lot of CO2, which escapes slowly throughout the following weeks. This is also the reason for the valve on the coffee bag (it's not there so you can smell the coffee): CO2 can leave the bag, which won't inflate, and oxygen won't get into the bag, which prevents a quick oxidation. Back to freshness. If you drink coffee right after roasting, it contains too much CO2 and this will affect your extraction, so you want to avoid super-fresh coffee, especially so when using an espresso machine (as opposed to, say, a v60 pour over brew).
3-5 WEEKS AFTER ROASTING
Most coffees taste the best three to five weeks after roasting. This applies to both espresso and filter roasts and most brewing methods. For filter coffee, using coffee that's too fresh is less of an issue. The extraction can turn our really great even with really fresh coffee, but the aroma and flavor do usually improve within the next couple of weeks. After those 3-5 weeks, the coffee does not just turn bad instantly, but it loses aroma gradually from week to week. At week 10, if the bag was unopened before, expect coffee to still taste better than just a few days after roast! Even after a couple of months, coffee can be consumed without any problems and it can still taste great. If you use pre-ground coffee, freshness is lost much more quickly, which is why it's best to grind coffee right before brewing.
IS TOO FRESH REALLY BAD?
While filter coffees can be drunk as soon as a day after roasting without any problems and taste great (though they will get better later on), we recommend to wait around two weeks before brewing fresh coffee on an espresso machine (if possible, of course). Your espresso extraction will most likely be influenced strongly by the CO2 and your espresso might be both under- and overextracted at the same time (google «espresso channeling» to find out more about the topic). There are ways to improve your results with really fresh coffee, like letting your coffee sit for perhaps 15 minutes after grinding before you use it in your espresso machine. This speeds up degassing of the coffee, but it's obviously not ideal and not very practical.
THE BEST WAY TO STORE COFFEE
So the CO2 and other gases can escape from the coffee bean, most packages are equipped with a one-way pressure valve. Due to this, air does not get inside, but gases can leave the bag. Thus, the bag does not inflate like a balloon when gases are released from the coffee. Therefore, ideally, coffee is stored in the original bag it was in at the time of purchase (as long as this is an airtight bag with pressure valve). There are a few exceptions, in our opinion:
- Older coffee, once opened: For coffee beans which are a few weeks older and have thus released most of the gases already, once the bag was opened.
- Frequent opening of bag: If you frequently open a bag over a longer period of time to take out a small amount of coffee, oxygen is getting inside each time you open it.
In these cases, vacuum containers such as the Fellow Atmos are a great solution. This kind of container creates a vacuum to protect the coffee from oxidation, thus prolonging its lifespan.
CONCLUSION
- Coffee usually reaches its full potential 3-5 weeks after roasting.
- Avoid drinking espresso roasts within the first two weeks after roasting, if possible – plan ahead when buying.
- Maybe try your filter roasts soon after roasting to find out how the aroma and flavor change over time.
- Shelf life is usually more than a year, when stored in a dry and cool place, or much more for most coffees.
- When it comes to aroma and flavor, it's best to finish a bag of coffee within 2-3 months.
- Keep coffee in its original bag with pressure valve and zipper if consumed within a few weeks, or store in a vacuum container if kept for longer.