When asking coffee experts about improving the taste of your coffee at home, many would start by suggesting that you buy fresh coffee from a local coffee shop or roastery. Buying coffee fresh ensures that all the flavor and aroma are still present in the beans, but what makes coffee beans fresh, how long do they stay fresh, and can they be too fresh?
This is a tricky question as many factors play a role in determining the optimal window of freshness such as raw coffee freshness, the density of the bean, and roast level to name a few. In general, the main factors that determine whether your coffee is fresh are CO2 levels present in the beans and oxidation levels.
If you are in a hurry and can't stick around for the full article, the quick answer is coffee beans are freshest between 2 to 14 days after roasting barring any packaging techniques used to slow the aging process such as vacuum sealing and nitrogen flushing (Brewing Market doubles down and uses both methods to ensure optimal shelf-life of your coffee).
For those that want to know more, read on to learn the why and how of the two major factors that determine freshness.
CO2 & The Importance of Degassing
Raw (unroasted) coffee contains CO2 and more CO2 is produced when the bean is roasted due to the breakdown of amino acids within the bean. This gas is released slowly as the beans rest and at a rapid rate during the grinding and brewing process. If you love the invigorating smell of coffee, you can thank the CO2 for carrying that aroma to your nose. The gas is vital for bringing aromatics to the surface which enhances the flavors in the cup; however, too much CO2 will hinder the water's ability to extract flavors by acting as a barrier between the water and ground coffee.
To balance this double edge sword, coffee beans need time to degas allowing for the release of some CO2; without this period of rest, coffee can be too fresh which negatively affects the taste of your brew.
The optimal rest time coffee needs to degas is between 2 to 10 days after the roast date. Coffee brewed when too fresh, i.e. before the 2 to 10 day window, will release an overabundance of CO2 hindering the extraction capabilities of the water resulting in a highly aromatic cup with a bitter and bland flavor. In other words, the escaping CO2 will fight the entering water and leave your tastebuds disappointed. Fresher is not better in this case.
Coffee is also plagued by another type of gas, oxygen.
When exposed to oxygen, coffee begins to oxidize causing the acids, sugars, and oils to degrade. This process starts as soon as the beans are exposed to the environment and will continue unless they are deprived of oxygen which we will talk more about in the packaging section.
The oxidization process starts slow and rapidly increases 14 days after being exposed. You may notice your coffee loses acidity, gains sweetness, and ultimately turns bland or bitter as time passes. Oily coffee such as dark roasts may deteriorate faster as the coffee is more porous and the oils present are highly susceptible to oxidization. oxidized coffee oil can lead to a rancid taste in your cup. To slow this process, it is best to store your coffee away from oxygen, moisture, and heat; the latter two speed up the oxidation process. Look for a nice airtight, dry, cool place to store your beans.
Luckily, the coffee industry has methods to stop and slow oxidation through its packaging methods.
Certain packaging methods can slow and even stop the oxidation of your beans by removing oxygen from the bag through vacuum sealing and/or nitrogen flushing. Vacuum sealing uses a machine to remove oxygen from the package before sealing the bag leaving your coffee beans oxygen-free.
Nitrogen flushing is the addition of nitrogen to displace any oxygen. Nitrogen is an inert gas that will not chemically react with the beans creating a barrier of protection around them. In Brewing Market's case, both are used to stop the aging process allowing you more flexibility with your coffee buying and usage.
These methods will keep your coffee safe while sealed. Once opened and exposed to the environment, it is best to store your coffee in an airtight container in a dark cool place and use the coffee within 14 days.
Everything in this article so far has been referring to coffee beans in a whole bean form. Once ground, the coffee loses its freshness at an alarming rate.
Whole vs Ground
To prolong freshness, it is best to keep your coffee in whole bean form until you are ready to brew. Once ground, the coffee is more porous which increases the rate of degassing, and has more surface area which increases the exposure to oxygen resulting in a loss of freshness within 15 minutes. The packaging methods stated earlier will stop the oxidation process while sealed, but remember that when the bag is opened, the clock starts again. If possible, always buy and store your coffee in whole bean form, and grind no more than 15 minutes before you brew.
Sum Things Up
Coffee beans are at their freshest 2 to 14 days after roasting. This time frame ensures the beans have an optimal level of CO2 to offer you an aromatic experience and still allow for the full extraction of flavor, and minimizes the level of oxidation that degrades your coffee's flavor.
A coffee roaster may package their beans to slow the aging process, and it is best to keep them in their original sealed bag until you are ready to start using them. Once open, store your coffee beans in an airtight container away from moisture and heat.
Remember that coffee is to be enjoyed and taste is subjective so don't be worried if you like the taste of your coffee after 14 days. Fresh coffee is delicious, but as long as your tastebuds are happy, drink coffee however you like!