[Breathing] Coffee beans: Growing beans is not as easy as you think

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The fresher the coffee, the better...right? Well, that's not entirely true.

Although no one wants to drink expired old beans, the flavor of roasted coffee beans brewed directly will definitely disappoint you because the coffee is still in the process of venting a lot of gas.

Whether you are a roaster or brewer, you must understand degassing. In this article, let’s understand what degassing is, how degassing affects the coffee you brew, and how to perform these actions.

Coffee beans waiting to cool after roasting. Neil Soque

What is exhaust?

Degassing is the process of releasing gas from coffee beans after roasting. When you roast coffee, a large amount of carbon dioxide and gas is produced inside the coffee beans.

A lot of gas will be released in the first few days after roasting. The problem is that these gases will release small bubbles when you brew, which will affect the coffee you brew. These bubbles will destroy the contact between the coffee powder and water, resulting in uneven extraction of flavor and aroma substances.

In other words, if you brew freshly roasted coffee, these gases will negatively affect the flavor of your coffee.

For this reason, it is a good idea to wait a few days after roasting before brewing the coffee. The period of time during which carbon dioxide is released and chemical changes occur is called degassing.

Fresh coffee beans. Source: Julio Guevara

Why does coffee have carbon dioxide?

When coffee is roasted between the first and second cracks, the beans will undergo a degradation reaction, and at about 220°C, the sugars will break down into several different compounds, including carbon dioxide. The beans will begin to turn brown because the water loss will also decrease.

Ensei Neto, founder of The Coffee Traveler, told the author that the degradation reaction is the most important chemical reaction at the end of roasting because when the degradation is converted into sugars, gas is produced when energy is released.

Cross-sections of roasted coffee beans showing different degrees of expansion. Source: Ensei Neto

Exhaust for perfect coffee

But the carbon dioxide in coffee beans is not a bad thing. It plays an important role in the quality of coffee. The Journal of Agricultural and Food Chemistry in 2018 mentioned: "Carbon dioxide is an important indicator of coffee freshness. It plays an important role in shelf life and packaging. It affects the process of coffee extraction, the formation of espresso crema, and may also affect the sensory flavor characteristics of coffee."

When coffee beans are over-vented, the flavor will be less distinct. The secret is to vent the beans for a moderate amount of time, rather than waiting until the beans are too old and old before using them. Juan Mario Carvajal, founder of the South American Specialty Coffee Association, said: "The gas that is still being released is an indicator of the freshness of the coffee beans, but when the coffee is too fresh, it will prevent the coffee powder from being fully extracted."

If you use beans that have not been degassed long enough, it may take longer to extract a shot of espresso because the gases will hinder the flow of water. These gases help to form crema because they will create bubbles during extraction, but the flavor will also be less ideal because the gases will also interrupt the extraction process.

Joe Behm, president of Behmor, which makes SCAA-certified home roasters and smart brewers, says venting is important because it makes the coffee flavor brighter.

He gave the example of roasting a Guatemalan coffee on his award-winning Behmor 1600 Plus, where after 72 hours the coffee had a rubbery taste, but after 96 hours the chocolate notes became apparent and the flavor framework was more fully established.

Coffee beans roasted using the Behor 1600 Plus. Source: Behmor

How long does it take to exhaust?

Exhaust will disperse the carbon dioxide produced by the coffee during the roasting process, but we don't want these gases to disappear completely. Instead, we want the gas content of the coffee to be just right when we want to drink it. The right amount of carbon dioxide will make the coffee taste less bland.

But how long to keep the coffee beans after roasting depends on many factors. Usually, three days to two weeks or three weeks after roasting are suitable for brewing. However, the differences between each type of coffee will also make the required degassing time different. The brewing method, processing method, and roasting degree will affect the length of the degassing time.

“There will always be some differences in how the coffee cherries are harvested and washed, and there will be differences in the drying process and water quality, so I think that’s why the degassing time will be different,” said Sharayah Harper, co-founder of Uncharted Coffee Co in the United States. “There are also different sizes of coffee beans, so the amount of water and gas contained in them will also be different.”

Roasted coffee beans stored in tins. Source: Maria Fernanda Gonzalez

The brewing method determines how long the bean-raising period is

If the coffee beans are for hand brewing or French press, they can be used up as soon as possible within a few days after roasting, because the coffee has a longer contact time with water, so there is no need to exhaust too much gas.

On the contrary, when we make espresso, because the brewing time is very short (usually only more than 20 seconds), it means that bubbles will affect the extraction results to a greater extent.

Joe said: "Espresso is very special. It requires a longer bean-raising period. You won't see people taking freshly roasted coffee and directly extracting it into espresso. The key is to raise the beans and exhaust the air so that the coffee can bring out its flavor when brewed."

Mark Michaelson, the head roaster at Onyx Coffee Lab and the 2017 US roasting champion, said: “For espresso, we usually want to use the coffee five to seven days after roasting, so that it is easier to extract the coffee. For pour-over, the time is shorter.”

He also said that when Onyx Coffee prepares beans for competitions, they usually wait 10-21 days before using them because it is easier to extract the coffee. If you can wait at least three to five days after roasting before using the coffee beans, it can help prevent problems with inconsistent coffee extraction.

Filling the portafilter with ground coffee, ready to brew espresso. Credit: Neil Soque

Coffee processing methods affect the growing period

The three main coffee processing methods: washed, natural, and honey processing, will also affect the degassing of coffee. Mark said: "We believe that natural coffee beans need a longer degassing period than washed ones."

“If you brew natural beans three to five days after roasting, they are often too fresh. Natural beans need more time to degas.”

The SCAA-certified Behmor 1600 Plus and Behmor Connected Brewer. Source: Behmor

The degree of baking affects the exhaust time

Dark roasted coffee will accelerate the degassing of coffee beans because the coffee beans are more degraded. The sugars are converted to a greater extent and there are more small cracks that cause more carbon dioxide to be released.

“Light roasted coffee beans are closer to being unroasted, which means that lighter roasted coffee beans need more time to degas,” Sharayah said.

Ensei also reminded me that if the coffee beans are not roasted evenly, it may lead to uneven development of the coffee bean material; the difference in degradation time will affect the degree of development of the coffee beans, and then affect the speed of exhaust of the roasted beans.

Sharayah prepares to roast coffee from Tolima Planadas, Colombia. Source: Sharayah Harper

How to maintain the freshness of coffee beans

How can you make sure that the coffee beans have been properly grown before you drink it?

Sharayah recommends developing a good organizational system so your coffee beans don’t sit around for too long. “Having an accurate record of roast dates is very helpful, especially when you’re roasting large quantities of beans.”

Mark said that Onyx uses nitrogen to fill coffee bean bags. With nitrogen, the shelf life of coffee beans can be maintained longer.

It usually bags the coffee 20 minutes to an hour after roasting, but the premise is that the coffee bean bag must have a degassing valve. When customers receive our coffee, it is usually three days after roasting. The degassing valve is to allow the coffee beans to be properly degassed during transportation and prevent the bean bag from bursting if there is a collision.

Freshly roasted coffee beans are taken out. Source: Behmor

The secret of exhaust and bean cultivation in home-baked coffee

Some coffee roasters may not have the equipment to fill nitrogen, but they will not have the problem of roasting large quantities or long-distance transportation.

Joe explains: “If you roast coffee with the assumption that it starts to lose flavor within seven days of roasting, you’re going to lose something in the coffee on the eighth day. I roast as soon as I open the can of green beans and leave it for four days. I just use the natural cycle so that the coffee doesn’t roast too much at once, so that I can drink the best coffee.”

He also uses large yogurt jars to store roasted coffee beans. He said that because they are not sealed, the beans can be degassed. They will not be affected by sunlight because the white plastic material on the outside is light-proof. For Joe, this is an ideal storage container (Translator added that due to different humidity and climate conditions in different countries, Taiwan's environment is relatively humid, so it is recommended to store coffee beans according to the store's storage method).

Many people also encourage the use of sealed cans to store roasted coffee beans to maintain the freshness of the coffee. But I would like to remind you that if you roast coffee beans at home, the storage container must allow the coffee beans to emit carbon dioxide. At the same time, you must consider the amount of coffee beans roasted and whether you can use them up in a fresh state.

The green beans are placed in the roasting drum. Source: Behmor

Successful venting can make the difference between a great tasting or disappointing cup of coffee, but it’s not that complicated. Just pay attention to the roast date and allow the beans to release the right amount of CO2.

So remember when the coffee beans were roasted, and consider storage space and brewing methods, which will also affect degassing. The degassing time required for each type of coffee bean is also different, and some will take longer to degas. If the flavor of the coffee is not as good as you expected, try to leave it for a few more days to degas, but be careful not to leave it until it becomes expired.

Translated from Perfect Daily Grind

Translated by Cheng Zhen Coffee

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