The only thing better than the smell of freshly roasted coffee? The flavour and aroma of your first brew of it a week or so later.
The idea that freshness can be an issue seems counter-intuitive, but there is very good reason to wait before brewing up your first coffee. If your coffee has been roasted too recently, it will not be your friend when it comes to consistency in both how it tastes and how well it behaves brew on brew. This problem arises from a byproduct locked into the beans during the roasting process – carbon dioxide. It is an excess of that most popular of greenhouse gases that causes these issues with consistency.
It’s this trapped carbon dioxide that makes up the crema on the surface of your espresso and the bubbling action of the bloom of your handbrew. It’s also why your unopened bag of coffee seems to have inflated a week after purchase. This is the carbon dioxide escaping the beans. We recommend allowing at least a week, two if you can, for this process to occur before drinking your coffee.
Not all carbon dioxide is necessarily bad. Unless you leave your beans a long, long time, there will always be some carbon dioxide inside your beans. And though crema tasted by itself is frankly nasty, to some it’s an important part of what makes espresso espresso. It’s an overabundance that causes problems.
What are the issues with too much carbon dioxide? Volatile compounds piggyback along with the carbon dioxide. If you don’t let it degas before brewing, those volatile compounds affect the behaviour of your brews, and thus the consistency from cup to cup and even the flavour. These compounds can make a coffee taste over-roasted and present as other undesirable flavours.
This is even more true of espresso, as the more volatile nature of espresso with all those high pressures means anything that complicates this further can have a big impact. The locked in gas is released as water hits the coffee grounds, some dissolving into the liquid and presenting as crema in the cup. In unrested coffee, the increased volume of volatile compounds, when forced by pressure into the liquid, affects flavour erratically as more is present in the end cup, replacing other more desirable flavour compounds.
Whether you’re a homebrewer or a coffee shop owner, planning to include a rest period to avoid these unwanted side effects will benefit your tastebuds in the long run. Getting your coffee orders in while you’re still finishing off your previous delicious beans also avoids that awful no man’s land of running out of coffee, suffering withdrawal and resorting to that mystery pot at the back of the cupboard to sustain yourself until help arrives.