This article originally published in The Sturbridge Times, February 2020 By Elvis Dyer, Owner/Roaster, Sturbridge Coffee Roasters
There is nothing like fresh roasted coffee, however, brewing a cup of coffee with beans that have literally just been roasted may not give you the best brew, and coffee degassing is to blame. Coffee degassing can greatly impact your brew so you should be aware of why it is important.
What is coffee degassing?
Degassing is the release of gases from roasted coffee. During the roasting process, gases, including a lot of carbon dioxide, form inside the bean. A lot of these gases are released in the first few days after roasting. This is why a coffee roaster always recommends beans not be used for at least 48 hours after roasting.
The escaping gases can result in small bubbles when you brew your coffee. These air pockets can impact the contact between the coffee grounds and the water. This causes an uneven extraction of the flavor and aroma compounds in the dry coffee. Simply put, brewing coffee right out of the roaster can negatively affect the flavor and profile of the coffee.
Many coffees don’t even hit the shelves for sale for a few days after roasting. This allotment of time, and the chemical release that happens during this time, is known as degassing.
Why is there Carbon Dioxide in Coffee?
During the roasting process, coffee beans undergo many chemical reactions. Complex carbohydrates are broken down into smaller molecules, beans begin to brown, and water vapor and carbon dioxide are created. The “first crack” a coffee roaster hears or see is the build-up of gases causing enough pressure to break the bean’s cell wall. And, the development of gases continues throughout the roast. At the end of roasting, the conversion of sugar happens. When this energy is released, it makes gas.
Carbon dioxide in your beans is not a bad thing and plays an important role in the quality of your coffee. This carbon dioxide is an indicator for freshness, plays a role in shelf life and packaging, impacts the extraction process, and is involved in the formation of crema in your drinks. This carbon dioxide may also affect the sensory profile in the cup. Too much degassing and the flavors are less vibrant. Gas still being released is an indicator of freshness. However, that degassing process does need some time, as using your beans too quickly after roasting will prevent the coffee grounds from being fully extracted, whether it’s in your coffee maker or your espresso machine.
How much time is ideal for degassing?
Degassing coffee really allows the flavors in your beans to shine. You need enough time for some carbon dioxide to be present as the right amount of carbon dioxide is what stops the coffee from tasting stale and flat. Generally, somewhere between three days and two weeks after roasting is considered the best window to brew coffee. Every coffee is different, therefore, the degassing period needed will vary. And the brewing method, processing choices and roast profile all impact how long this is. For example, a dark roast accelerates degassing because the bean has degraded more. The sugars have had more opportunity to be transformed, and there are more tiny cracks allowing the carbon dioxide to be released. Whereas a light roast has more of the bean intact and may need to degas for longer.
How the bean was grown impacts the degassing process, as the harvesting and washing process is different for each bean.
Fresh roasted coffee truly is one of the best cups of coffee for you to enjoy. Make sure you know when your beans were roasted and that they have had time to degas.