Resting time

I am not talking about our coming vacations 🙂 but about letting the coffee rest between roasting and brewing. How fresh is fresh and should we brew immediately after roasting? These are common questions that I get from my costumers. The first question I answered in a previous blog:

I always recommend my costumers to use fresh roasted coffee and so I sell coffee that is roasted-on-demand which implies that I don’t have a storage of roasted coffee. However, sometimes it happens that i get a coffee order accompanied by an email with subject: urgent. In these cases it takes a bit of explanation to the customer that I really cannot ship that coffee first thing in the morning since I actually first have to roast it.

But to return to the topic: should you brew the coffee immediately after roasting? Personally, I think coffees taste the best not shortly after finishing the roast but after another 2 to 4 days.
During roasting the coffee beans undergo physical and chemical changes. Due to the chemical reactions taking place during roasting CO2 (carbon-dioxide) is produced which is initially retained in the beans. This CO2 will be released over a period of weeks after roasting, the so-called degassing. The speed of degassing is inversely related to time after roasting: fast degassing takes place during the first hours after roasting and slowing down gradually. Adding hot water to coffee will release some of the CO2 that is still bounded to the bean structure and we can « see » this CO2 in the crema formed while brewing the coffee.

If you brew your coffee with an espresso machine then this fact is very important for you. Espresso brewing takes places under high temperature and pressure, so if there is alot of carbon-dioxide left in the coffee beans it would make the brewing process more difficult and can prevent the proper extraction of the coffee flavours. It will also lead to an excessive amount of crema and sometimes the espresso cup may have more crema than actual espresso which is a clear indication that the coffee has not rested long enough.
For other brewing techniques as for instance filter-coffee this can still be an issue since the coffee will swell-up from the release of CO2. In an open-drip filter this wont be a problem but in closed-dripping as a common electrical filter machine it may lead to the machine to overflow.

You can also use the release of CO2 as a freshness factor! If you prepare an espresso and the crema is too thin and even shows holes through which the espresso liquid underneath is visible then you know the beans are no longer fresh, since most of the CO2 has been released already. The same counts for filter coffee: if the coffee remains flat during the brew cycle, the coffee is old.

The coffee I roast and send always mentions the roasting date, which is typically 2-3 days earlier than the day you receive your package. Though it is tempting to immediately open the package and prepare some coffee, it may actually be better to wait a few days more to get the best flavour. Therefore it’s recommended to not wait with your new coffee order until you really run out of coffee, because otherwise you may find yourself in the antagonizing situation that you can’t make your favourite cup of coffee since you run out of the previous coffee while the new coffee you just received is actually still too fresh to use.