Coffee Degassing – Fresh vs Too Fresh

Everyone wants their coffee fresh, but you might be missing out on some real flavour if it is too fresh. It is like a cake just out of the oven – if you let it cool off, you will actually taste it more. For coffee, cooling off is known as ‘de-gassing’ or ‘resting’.

Degassing is the release of gases from the inside of roasted coffee beans. The roasting process breaks down carbohydrates in the green beans, producing vapour and carbon dioxide as part of the chemical reaction that occurs. This vapour and gas are naturally released from the beans in the days after roasting and can massively impact how your coffee tastes.

Brewing too soon (during the degassing period) means the excess of gas will be released into the brew. The gases create small bubbles which cause an uneven extraction. Water will always take the easiest route through the ground coffee and these bubbles cause gaps, meaning a quick exit for the water and a subpar cup of coffee. Typically, we allow at least 3 days for degassing before using roasted beans instore. This means that once ground a lot of the gas has already left the bean, we can find a consistent recipe and the true flavours of the roast come through.

 ‘Blooming’ is very important at this brewing stage – especially for newly roasted beans. It releases the last of the built up gas, creating an even extraction and pulling the best flavours from the roast. This is most typically seen in V60 set ups where you often see the coffee being pre-wet and allowed to sit for 30 seconds. It creates an even base for the remaining coffee to pass through, with as few shortcuts for the water as possible.

Why you should not pre-grind your beans to speed up degassing!  

If you decide to grind your coffee well before brewing, degassing significantly speeds up, but not in a good way! The finer the grind, the larger the volume of gas that is released. This makes your coffee stale in a matter of hours because the cells that have stored these gases have been broken up and released. Not only are you speeding up the de-gassing process but you are also speeding up the oxidation process by exposing your coffee to oxygen.

What happens when you brew freshly roasted coffee?

The fresher your coffee, the more degassing you will experience during your brewing process. If your beans are too fresh (i.e they have not been given enough time to properly de-gas) regardless of how you choose to brew your coffee the extraction will be uneven due to the overwhelming amount of CO2 trying to escape. When it comes to brewing your coffee, we recommend to bloom (pre-wet and let sit for 30seconds) your grounds to release any rapidly escaping CO2.

What happens once beans have degassed?

Like fine wine, freshly roasted coffee gets better with time (to an extent). After degassing for the first few days, oxygen starts to penetrate the beans. This process is called oxidation and is the main cause of staleness. One way to prolong the flavour and freshness of your coffee is to store it in a container with a one-way valve. This way the CO2 released from the beans can escape and oxygen will not be able to easily find its way in.

Takeaway message- when it comes to freshly roasted coffee, brewing with beans straight out of the roaster is not recommended (well not if you are wanting the best possible brew!)

Let them rest, de-gas and enjoy an even better brew in a few days!

Written by Charlene Thompson