How To Decaf Coffee {A Simple Guide}

Along with tea, coffee is one of the most popular drinks in the world. Many people like the taste and flavour but cannot stand the effects of caffeine. Fortunately, there are a few methods to help you enjoy the beverage without this controversial stimulant. Read on to learn how to decaf your coffee.

What is decaf coffee?

Decaf coffee is a short word for decaffeinated coffee. It is a special type with the removal of at least 97% of the caffeine from the coffee beans during the processing.

There are many methods to decaffeinate coffee. These include the Carbon Dioxide Process, the Swiss Water Process, the Direct-Solvent Process, and the Indirect-Solvent Process. Most of them include carbon dioxide, organic solvents, or water.

The beans should go through the decaffeination process before you roast and grind them. The nutritional value of regular coffee and decaf coffee is almost the same, except for the caffeine levels. Nevertheless, the smell, taste, and colour can be a bit different, depending on the technique applied. This makes decaf versions a better option for those people who cannot stand the bitter flavour and taste of regular types.

The Roselius process and early history of decaf coffee

Caffeine could be removed from coffee beans. However, it is not a simple process as many people might think. The first person to come up with a practical technique was Ludwig Roselius, the German head of a coffee firm.

In 1903, his coffee shipment was soaked with seawater during transport, which leached out the caffeine but still retained the flavour. He tried to repeat this by steaming coffee beans with different acids and eventually using benzene as a solvent for the extraction. After many trials and errors, the first decaffeinated coffee was invented and patented in 1906.

However, benzine can be a carcinogen to humans. This means the substance might increase the risk of forming cancer. That’s why this method is no longer common these days.

Why do we need to decaffeinate coffee?

how to decaf coffee

Caffeine is a natural component in many foods and drinks, especially chocolate and tea, but it is especially typical of coffee. This is an appetite suppressant and stimulant that can make you alert for working or study during the night.

However, it has some side effects, too. Many people experience muscle tremors, racing heartbeat, excess sweating, diarrhoea, insomnia, or anxiety when consuming too much caffeine. Excessive caffeine consumption also increases the risk of miscarriage in pregnant women.

Decaf coffee is a great solution to this problem. You can enjoy the drink regularly without worrying about high caffeine content and its effects. Indeed, this is one of the main reasons why this type has become much more widespread over the past decades.

Keep in mind that the decaf process does not completely extract all of the caffeine content. In fact, it only needs to remove at least 97 per cent of caffeine from the beans. That means an average cup of decaf coffee, which typically contains around 180 milligrams of caffeine, might still have 5.5 milligrams of this stimulant. The exact amount can vary, depending on the bean categories, processing methods, and other standards.

Similarities of decaffeination processes

Before diving deep into each decaffeination process, let’s take a look at the basic principles to remove caffeine from coffee beans.

Firstly, they always decaffeinate the beans in an unroasted or green state. Many people think that roasting and grinding the coffee into powder beforehand would make it simpler to extract caffeine. However, this is not actually true. If you try these techniques with roasted versions, you would end up with something that tastes like straw.

A common challenge of decaffeinating coffee is to remove caffeine without affecting other components. This is a challenging task because coffee beans contain more than 1,000 substances. They make a significant contribution to the flavour and taste of the drink.

Another similarity is the use of water to moisten coffee beans. Caffeine is a water-soluble component. Therefore, soaking the coffee makes it easier to draw out the substance. But water can also remove other solubles like proteins and sugars. That’s why each method adds a different agent, such as ethyl acetate, carbon dioxide, activated charcoal, or methylene chloride, to minimize this effect.

Lastly, all decaffeination processes involve moderate temperatures to vaporize solvents. The ideal range should be between 70 and 100 degrees Celsius. This can ensure there are no residues of chemical solvents, which can pose some health risks.

4 common methods to decaffeinate coffee

There are 4 common methods for decaffeinated coffee. We can basically divide them into two main groups: solvent-based and non-solvent based.

1. Solvent-based processes

As the name implies, solvent-based processes remove caffeine with the help of a chemical solvent, notably ethyl acetate or methylene chloride. They can be in turn divided into the “indirect” and “direct” approach.

In the direct process, coffee beans are directly soaked in a solvent to remove caffeine. On the other hand, the indirect method moistens with water before treating with a solvent in the later stages. In this case, there is no direct contact between the beans and the solvent.

Solvents used to decaf coffee

A solvent is a chemical that aids in extracting and removing the caffeine selectively without affecting other compounds in the coffee beans. Two common options these days are ethyl acetate and methylene chloride.

Methylene chloride a colourless liquid that is highly volatile and can vaporize at high temperatures. Many experts concern about the health risk of the remaining traces after the decaf process. However, it is unlikely that they might survive the roasting procedure.

Ethyl acetate is another solvent option. It is a natural fruit ether extracted from acetic acid, which is the building block of vinegar. Compared to methylene chloride, this substance is safer and poses fewer health risks.

Direct-solvent process

In this procedure, we need to steam green beans around 30 minutes to open pores. Once they are more receptive, a solvent is used to soak the coffee repetitively in 10 hours to get rid of caffeine. The liquid is circulated around a container of green, moist beans.

An evaporator is used later to recapture the solvent, which vaporizes in high heat. Lastly, the beans are processed to remove residues by steaming, drying, and roasting.

In most cases, the direct-solvent process is done in batches. This means solvent can be added to a vessel, then circulated and emptied a few times until the beans achieve the proper levels of caffeine.

Indirect-solvent process

Unlike the direct method, in-direct solvent decaffeination begins with soaking the coffee in near boiling water. In a few hours, caffeine, oil, and other flavour compounds will dissolve gradually. After that, the water is separated and moved to another container filled with a solvent.

The molecules of the solvent can selectively bond with those of caffeine. This creates a mixture that can be removed with heat. Lastly, the solvent and water are separated. The beans are added back to the water to help reabsorb the flavour substances they lost previously. This method is more popular in Europe and often uses methylene chloride as a solvent.

2. Non-solvent based processes

Both solvent-based methods can result in some loss of flavour in the resultant beans. Therefore, some other techniques are created to deal with this problem. Two non-solvent based processes involve the use of water to remove caffeine.

Carbon dioxide decaffeination process

In normal condition, carbon dioxide is not an ideal solvent because it is in the form of a gas. Nevertheless, it can be turned into a supercritical fluid when compressed at a bit higher temperature and high pressure. Mixed with water, this substance can be a good option to dissolve the caffeine.

This approach is basically similar to the direct solvent technique, except that it uses another solvent. High-pressure vessels, often at approximately 250 or even 300 times the atmospheric pressure, are used to move the gas to a bed of moist, green beans. Under high pressures, carbon dioxide becomes a liquid and works as an effective solvent.

The most important benefit of this method is that carbon dioxide can be much more selective for caffeine rather than other flavour compounds. This means you can retain most of the essential substances that contribute to the aroma and taste of the coffee.

However, there are also some drawbacks to using carbon dioxide as a solvent. This supercritical liquid has the same density as a liquid, but the diffusivity and viscosity are the same as those of a gas. Those features noticeably reduce the pumping expenses. However, carbon dioxide decaffeination is a cost-effective method in spite of its very good yields. It is able to remove around 96 per cent to 98 per cent of the caffeine from the coffee beans.

In addition, it can be costly to operate. The high-pressure equipment requires a lot of expenses and expertise to set up and run. Therefore, this extraction approach is a good and commercially practical option only when you need to process more than 3,000 tons of beans each year.

Water decaffeination process

Another alternative to carbon dioxide is water decaffeination. This process can be divided into two main methods: French water decaffeination and Swiss water decaffeination.

As the name implies, they involve water processing. This means water replaces carbon dioxides and other chemicals to work as a solvent to get rid of caffeine from the beans. A battery extraction process is often used with 8 to 12 vessels. Each of them contains the beans at different decaffeination stages.

A mixture of green coffee beans and water that has already been decreased in caffeine is circulated within the extraction battery. After a period, we will separate and empty the vessel exposed to low-caffeine extract. In the next step, the decaf beans are rinsed and dried, while the vessel with fresh beans is placed on stream.

The caffeine-rich extract drawn off from the fresh coffee vessel is passed through activated charcoal to help absorb the caffeine. The charcoal is pretreated with sucrose or another form of carbohydrate to remove caffeine without affecting other flavour compounds.

The sucrose can block carbon sites that could often absorb sugars from the coffee extract. Overall, the water process decaffeination is more natural because it does not employ any chemical. However, it might remove less caffeine, around 94 to 95 per cent, compared to solvent-based methods.

Other methods to decaf coffee

how to decaf coffee

These four methods are the main processes for decaffeinating coffee these days. However, they are not the only options. There are still a few other techniques. Some can be their variations like using nitrogen oxide as a solvent to extract caffeine. Recent studies have also suggested surprising results. Some processes use microorganisms to help metabolise caffeine and remove the substance from the coffee beans.

Why is it not simple to decaf coffee?

Choosing a good decaf coffee can be a challenging task. The reason can centre around two difficulties during the decaffeination process.

Firstly, the soaking of coffee beans in water and solvents tend to remove many flavour compounds that contribute to the tastes and aromas of the drink.

Secondly, decaf coffees can be notoriously hard to roast. Though the beans go through the decaffeination process when they are in the green state, the process turns them into brown. As a result, roasters find it more difficult to control while roasting. They can respond exaggeratedly or inconsistently to applied heat. Also, decaf coffee beans contain less bound moisture content.

Understanding these challenges, you can choose better decaf coffee for your drinking experience. Overall, the roasting style you choose will affect the final taste rather than the decaf technique. And it is advisable to avoid products with too oily and dark textures.

The bottom line

Many people love caffeinated coffee, while others don’t. It is just a matter of personal preferences. Four methods in this post are the main ways to decaf coffee. However, they are not the only options. You can try a variety of other techniques to meet your tastes and preferences.

And remember that there is no completely caffeine-free coffee. If you really want to avoid this substance, perhaps it is better to choose another drink without a trace of caffeine in the first place.

References:

  1. https://link.springer.com/chapter/10.1007/978-94-009-3417-7_3
  2. https://www.researchgate.net/profile/Kulathooran_Ramalakshmi/publication/12783410_Caffeine_in_Coffee_Its_Removal_Why_and_How/links/55011f840cf2d61f8211e411.pdf
  3. https://pubmed.ncbi.nlm.nih.gov/10516914
Vincent Lee
Coffee is an indispensable part of my life. I love brewing simple coffee recipes at home with fresh ingredients and enjoy every moment. This blog is a great chance to share my passion and encourage everyone to make better coffee.

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