Everybody knows things are better fresh. But why is coffee fresh off the roast any better than coffee that’s been sitting on the shelf for a few months at the gourmet grocery? Why is it all that important to look at the “Roast Date” on bags of coffee you buy at retail stores? What––scientifically––does “freshness” even mean in the coffee context?
Have you ever had coffee that tasted like blueberries, oranges, roses, or jasmine? These flavors are actually aromas being given off by the coffee’s natural oils. When these aromas enter your mouth via your coffee, they rise up into your nasal passage and your brain interprets them as rich flavors. And this is where things get crazy...
You can only taste these complex, exceptional flavors for 1-2 weeks after the coffee is roasted.
To find the peak flavor of freshly roasted coffee, one needs to balance two important factors:
The loss of aromatics
The build-up of carbon dioxide
For most coffees, this happens in a window of 4-14 days after roasting.
Science Behind Freshly Roasted Coffee
According to Professor Chahan Yeretzian, the head of the Coffee Excellence Center at the Zurich University of Applied Science, "The aroma of the roasted bean... if you measure it, you see a loss of freshness between a few days, even one day." But, in the pursuit of peak flavor, there is more than aroma to consider. The immense heat of roasting breaks down sugars and amino acids into carbon dioxide. The coffee has to rest and degas before it becomes easy to brew. From Professor Yeretzian, "In the first week, [the coffee] evolves every day... from a CO2 perspective the first week is quite dynamic. I wouldn't think of it as aging; it's more a calming down." For coffee lovers seeking the most flavor, you should aim to balance the degassing of CO2 with the loss of important aromatics.
For coffee lovers seeking the most flavor, you should aim to balance the degassing of CO2 with the loss of important aromatics.
For darker roasted coffees, this period usually starts after the first few days after roasting*. For lighter roasted coffees, it's a good idea to wait a little longer before diving in, say 5-10 days. This is because dark roast coffees are more porous than light roast after spending more time in the roaster.
Coffee Freshness and Peak of the Flavor Chart
Source: Boot Camp Coffee
It's important to consider how you'll be enjoying your coffee as well. For more gentle brew methods like drip or pour over, you can start using your favorite coffees a little earlier.
For espresso, it's important to give the coffee a bit more time to rest before subjecting it to an intense, pressurized brewing environment. *Something to consider: a very dark roasted coffee will have oils on the surface of the beans. This exposure of the coffee oils to air leads to fast oxidation of those oils, which can cause rancid flavors. Another good reason to not wait to brew your favorite dark roast. Now that you know the science behind freshly roasted coffee. Go grab one!
Source: Clive coffee