From the recent experiments we have been doing, we have found something interesting related to the aging the single origin coffees. We normally have a recommended range between 7 days and 21 days for the single origin coffees. But what we have found from the experiment was surprising.
What has been found is that there is another peak of flavours after 3-4 weeks, before it goes completely flat and dull (depends on the bean). After the coffee is roasted, CO2 starts to escape from the bean. While the CO2 is coming out, it brings some molecules that affects the flavour. The amount of the CO2 and other elements is increasing for a few days and reach the peak. After the peak, the amount is gradually decreasing and the extraction status becomes stable. This is where we find the best window for the coffee, in general. And this is roughly between 7 and 21 days.
When the most of CO2 is out of the bean, the extraction status is changed and some new nuance can come out. As resistance by CO2 is lowered, the ground coffee absorbs water faster hence the speed of water flow during the extraction becomes faster, which, therefore, enhancing the acidity and complexity. At this point, if we change the grinding a bit finer to extend the brew time, this will increase sweetness as well as mouthfeel of the coffee.
The characteristics of the second peak is different to the first peak which is vibrant, aromatic, and more impact. Instead of this, the second peak is more rounded, sweet and balanced.
If you have not tried this, it would be good to try to age your bean for 5-6 weeks and taste it.