Coffee Degassing: All You Need To Know

coffee on counter open container

If you are a person who enjoys excellent coffee, you may have gone to the extent of purchasing a home roaster to roast your own coffee beans to ensure that every cup that you brew is perfect. Not many coffee roasters are well informed about coffee degassing and how important it is, which means that it is an often neglected practice. What do you need to know about coffee degassing?

Coffee degassing allows carbon dioxide gas in roasted coffee beans to escape, enabling the beans to be brewed properly. Different beans and roast profiles degass at different rates. Degassing too much or too little will ruin the flavor of the coffee. Degassing well is vital for a good cup of coffee.

Coffee degassing is an often-overlooked process in preparing coffee beans for brewing. Coffee beans must be degassed to ensure that the coffee can be brewed to perfection. Without degassing, the coffee will be nothing but disappointing. Let’s go over all that you need to know about coffee degassing and why it is important.

What Exactly Is Coffee Degassing?

During the roasting process, the physical characteristics of coffee beans change. The heat of the roasting process causes the complex carbohydrates to present within coffee beans to break down, and this physical breakdown causes the release of gasses from within the coffee beans themselves.

These gasses mainly consist of about 90% carbon dioxide and 10% other gasses such as nitrogen. Carbon dioxide is the problem gas for coffee beans.

These gasses are detrimental to the brewing process, and so they ruin the taste of the coffee beans, resulting in a poor cup of coffee.

The process of degassing coffee beans is simply allowing the majority of these detrimental gasses to escape from the coffee beans before grinding them and using them to brew a cup of coffee.

Allowing the gasses to escape ensures that the coffee can be brewed well, making it possible to dial in the perfect flavor profile from the roasted coffee beans.

Degassing coffee beans takes time, and it may seem like a futile exercise, but it is well worth it for the sake of an excellent brew. There is an art to the process, and different beans and roast profiles require varying amounts of degassing time before they are ready to be brewed.

The challenge of degassing is knowing when to grind the beans for brewing without letting them degass for too long. Not degassing enough can ruin your beans, but degassing too much can spoil them as well.

Take the time to learn how to degass your coffee beans properly, and it will take your home roasting and brewing experience up a level.

Why Is Coffee Degassing So Important?

The importance of degassing coffee beans has everything to do with the brewing process of the coffee and little to do with pretense, as many seem to think.

If coffee beans are not allowed to degass before being ground for brewing, the gasses that are present in the beans from the brewing process will escape very quickly from the beans while they are brewed.

This may look impressive, and it often results in very satisfying looking crema, but this is a result of the rapidly escaping gasses from the beans, which ruins the flavor of the coffee.

The gasses escaping from the prematurely ground coffee beans effectively create a barrier between the coffee and the water, which prevents the coffee from extracting evenly during the brewing process.

Coffee that has been under-extracted has a sour or stale taste, which no coffee lover will ever enjoy.

The importance of degassing coffee beans is as vital as the roasting or brewing process of the coffee and should never be a step that is neglected by anyone who cares about the quality of their coffee.

How To Degass Coffee Beans

You may be glad to discover that the actual process of degassing coffee beans is not very difficult at all. The key factors for all who attempt the process is patience and timing.

To degass coffee beans, after they have been roasted, all that is required is to let them rest for the gas to escape from the means naturally.

Naturally degassing beans is the best method, as it produces the best brew, and attempting to accelerate the process is not recommended, as it is possible to degass coffee beans too quickly, which may ruin their flavor.

Simply place the roasted coffee beans in a container that will protect them from sunlight and heat and is not airtight.

It is important that the container is not airtight to allow the gasses that are released from the beans to escape. The container should be opaque to protect the beans from sunlight and heat, both of which promote oxidization of the beans.

For this reason, a clear glass jar with a tight-fitting lid is not ideal. If a glass jar is used, the glass should be dark green or brown, which will help to keep sunlight out, and then the lid should not be screwed on very tightly.

There are some home roasters that use white plastic tubs, such as the kind that yogurt comes in as they are not airtight, and the white plastic blocks out sunlight but repels heat which helps to preserve the beans well.

The best storage container for beans that being degassed is a bag or container that has a one-way valve. A container of this type will let the carbon dioxide and other gasses escape while helping to prevent air and oxygen in the air from being introduced to the beans.

Keep close attention to how long the beans are left in the containers and do not let them rest for too long before grinding them.

The length of time will vary depending on the beans, but a good rule of thumb is to never allow the beans to degass for less than four days and for no longer than fourteen days.

There are exceptions to this, as some beans can be used after only degassing for two days, and others may take up to three weeks to degass to the correct point before brewing. The process depends on the type of coffee beans, the size of the beans, the roast profile of the beans, and your preferred brewing method.

What Happens If You Do Not Degass Coffee?

If coffee beans are roasted and not allowed to degass before being ground and brewed, the flavor profile of the coffee will be significantly and negatively impacted.

The process of degassing coffee beans allows the naturally occurring gasses that form within the beans while roasting to be released. If this process is not allowed to happen in its own time, and the beans are ground before they are ready, the grass will escape too quickly.

Then the gas from the beans escapes too quickly; this allows for the oxidization process of the beans to increase rapidly.

The process of oxidation, simply put, is when air and the oxygen from the air fill the spaces within the coffee beans that were once occupied by the carbon dioxide and other gasses that are released during the degassing process.

When coffee beans become oxidized, they taste stale. This usually occurs if the coffee beans are allowed to degass for too long but occur almost instantly if the beans are ground before being allowed to degass properly.

For this reason, degassing coffee beans is a fine balance between perfect flavor and utter disappointment.

How Long Do Coffee Beans Take To Degass?

It is possible for coffee beans to degass for too long, and it is very easy to not allow them to degass for long enough.

The degassing process is an art that every coffee roaster must learn to master for themselves.

The process itself begins immediately after the roasting process stops, and the majority of the gasses leave the beans in the first few hours, but the remaining gasses can take some time to escape.

The size of the coffee beans and the roast profile of the beans play the most prominent roles in how long the beans take to degass.

Dark roasted coffee beans take less time to degass sufficiently than lightly roasted coffee beans. This is because the beans that have been roasted longer open up more and undergo a bigger change than beans that are lightly roasted, which allows more of the gasses to escape during the roasting process.

Larger beans take longer to degass, simply because there is more grass in the beans due to their larger size.

Beans that have been washed take marginally less time to sufficiently degass than beans that are allowed to degass naturally, but they then become stale quickly as well.

To put a number on it, coffee beans can take anywhere between two days and three weeks to degass, depending on their size, roast profile, and how the beans will be brewed.

Large coffee beans that are lightly roasted will take the longest time to degass sufficiently for grinding and brewing, and small dark roasted beans will degass more quickly.

If you buy whole roasted coffee beans from a roastery, ask them what the optimum degassing time for their beans is for your preferred brewing method, and they will be able to help you determine how long to degass the beans before using them.

If you roast your own beans at home, it will take some experimenting to get the degassing time of your preferred beans just right for the perfect cup.

How Does Degassing Work With Different Brewing Methods?

The brewing method that you intend to use for your coffee beans should be a factor in how long you allow them to degass.

The longer the coffee beans are degassed, the easier it is to extract from them. This means that quick brewing methods require coffee beans that have been degassed for a long time, and long-brewing methods can use beans that have not been degassed for very long at all.

Manual brewing processes such as french press and drip brewing do not require the coffee beans to be degassed for very long. Some coffee roasteries say that degassing their beans for as little as one or two days is enough for brewing methods that take a longer time.

Degassing for about four or five days is more than enough for these brewing methods, as the hot water remains in contact with the coffee grounds for a long time while brewing.

The amount of time that the water is in contact with the beans allows the beans to be fully extracted even if there is a lot of gas escaping from the beans.

On the other end of the scale, coffee grounds that are used to make espresso must be allowed to degass for a much longer period of time. The water that is used in the process of brewing espresso is in contact with the coffee for such a short period of time that the coffee will not fully extract if there is too much gas escaping from the beans.

For espresso, the coffee should be degassed for at least seven days, and for some lighter roasts, the minim degassing time is twelve to fourteen days.

For brewing methods that are somewhere in the middle, such as normal machine coffee or cappuccinos, the beans should be allowed to degass for four to seven days before being ground and brewed, depending on the roast of the beans.

If you roast your own coffee beans, it is simple to determine whether or not your beans have sufficiently degassed before grinding and brewing.

The method is to make a cup of coffee, and if the coffee tastes somewhat sour, the beans have not been allowed to degass for long enough. Leave these beans to degass for another day or two and try again.

If the coffee tastes stale and flat, the beans have been allowed to degass for too long. The next time you degass the same beans, grind and brew them a few days earlier.

This process is a learned skill, so do not be concerned if it takes some time to get it just right. Keep trying until you figure out what is best for your beans, and try to use the same beans roasted in the same way until you feel comfortable with the process, as a different bean and a different roast will change the process entirely.

Conclusion

Coffee degassing is vital. This process is far more important than many realize. There are even those among coffee enthusiasts who have never heard of coffee degassing, but this does not diminish its importance.

Without allowing coffee beans to degass before grinding them for brewing, the coffee will be ruined. Perfectly good beans can become unusable if not allowed to degass.

Degassing allows the coffee beans to rid themselves of most of the gasses that form during the roasting process. These gasses create a barrier between the beans and the water when the coffee is brewed, which results in uneven or under extraction, which produces sour coffee.

When the gasses from the beans are allowed to escape over a few days, when the beans are ground and brewed, the hot water can reach the entire surface area of the coffee without disturbances or blockages, allowing the coffee to be extracted evenly, resulting in a good cup of coffee.

However, be sure to not let the coffee degass for too long, or this will allow for too much oxidization that will cause the coffee to taste stale once it has been brewed.

Allow your coffee to degass, keep it in a container that protects it from the sun, taste the coffee as you go to determine the right moment to grind it and brew it, and you will find the right process for brewing the perfect cup of coffee from freshly roasted beans.
Sometimes fresh is too fresh, but perfectly degassed is just right! Treat your beans well, give them the time that they need, and you will never brew a bad cup of coffee again!

Tim S.

Tim loves roasting, brewing, and experimenting with coffee. After years of perfecting this craft, working as a barista, and owning a small coffee service in college, he has decided to share his knowledge with the world.

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