Coffee Resting: Why and How
There are so many variables involved in roasting coffee that oftentimes it feels like both science and art. There are also so many differing opinions regarding the coffee roasting process, sometimes in contradiction that can be confusing sometimes. Is fresh coffee the best, or is it better to leave it for a few days after roasting before brewing it? Does resting coffee really matter? What is the ideal resting period? In this blog we go over why coffee resting is important, and how many days we should let the beans rest after the roasting process is concluded.
Why coffee resting is important
Green coffee beans release moisture as they go through the roasting process, resulting in pockets of CO2 trapped inside the beans. This trapped gas is released over time during the degassing process, or when we grind and brew the coffee. The release of CO2 also serves as an indicator of the coffee beans’ freshness. Freshly roasted beans create a good quantity of froth when extracted for espresso or brewed, on the other hand, stale beans create almost no froth. In the coffee industry, this froth is called “bloom”.
By leaving the coffee to rest between 5 to 14 days after roasting, the trapped gas is allowed to slowly escape the beans, leaving the true flavors and aromas of the beans. After the coffee resting period, the baristas can extract the real characteristics of the coffee beans and not the acidity and sourness of the trapped CO2 when brewing the coffee. In addition, the aromatic compounds that give coffee its flavors and characteristics, also takes time to develop after the beans are out of the roaster machine.
Basic guideline for resting coffee
The ideal coffee resting time is achieved when CO2 is degassed while still retaining the flavors and aromas of the roasted coffee beans. It is commonly known that the degree of roast significantly impacts the rate of degassing in the coffee beans. Dark roasts degas and “stale” much quicker compared to medium and light roasts. Below are some basic guidelines for resting coffee based on the degree of roast:
- Dark roast: as fresh as possible, around 1-3 days coffee resting is sufficient. Starts to oxidize and the acidity increases after about a week.
- Medium roast: at least 7-10 days, usually lasts for a month or two before flavors deteriorate
- Light roast: between 10 – 14 days, the coffee can last for much longer without losing flavor or aroma
Note that there are other factors like oxygen exposure, heat, light and moisture that can speed up the “staling” process, so it is recommended to store the coffee beans properly. It is recommended to store the roasted beans in a sealed container and in an ambient environment with a lower temperature. However, avoid storing the beans inside the refrigerator, as the high moisture inside the refrigerator will speed up the oxidation process and diminish the flavor of the coffee. Another recommendation is to put as many details as possible on the container, such as roast dates, batch number and roast profile so the barista at work can easily pick the coffee beans to brew in their peak condition – CO2 out and flavors in. Coffee roasters and coffee distributors should roast the beans and immediately dispatch them, so the majority of the coffee resting period happens during the transport of the beans to the customers. Sometimes this can be indicated by the accumulation of CO2 inside the bag when they arrive at the destination.
In conclusion, coffee resting is recommended after the roasting process is completed. During the coffee resting process, trapped CO2 can escape the beans, sharp and astringent flavors soften out, allowing a cleaner expression of the coffee beans’ characters to shine through and give clarity to the brewed coffee.
