What is Decaf Coffee? The Process Explained

decaf coffee
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Decaf coffee is any coffee in prepared, ground, or bean form that has a majority of the caffeine eliminated from it using various decaffeination processes.

These processes do not make decaf coffee 100 percent caffeine free. However, they significantly reduce the amounts of caffeine in an average cup of coffee.

Some individuals choose to drink decaffeinated coffee in order to avoid most of the caffeine either out of personal preference, to reduce any jittery responses, or according to dietary recommendations.

The first styles of decaf coffee were made during the early 20th century by Ludwig Roselius, a German coffee merchant. He believed that his father was poisoned by drinking an excessive amount of coffee. So he patented his Roselius process in 1906. His process soaked green coffee beans in a solution containing benzene, which worked to remove caffeine from the beans.

However, the chemicals used in the process were not especially healthy (benzene is a carcinogen for humans), and the benzene soak method was ultimately replaced by other processes.

Let’s look at the four main decaffeination processes.

The Four Main Decaffeination Methods

There are two sub-groups that make up the four major methods: non-solvent and solvent-based. First, we will cover the non-solvent processes.

Non-Solvent Based Methods

1. The Swiss Water Process (SWP)

Any coffee that is decaffeinated using this method is labeled “Swiss Water” Decaf. To note, this is not the same thing as a Swiss Mocha.

This decaffeination process uses chemical-free water and was pioneered in 1933 in Switzerland. It was introduced to the market in 1988 in a Burnaby, BC, Canada facility.

It is very important to note that this is the only facility that is certified Kosher and organic. This method is used almost exclusively for decaffeinating organic coffee. It undergoes caffeine level audits on a regular basis to ensure it complies with being 99.9% caffeine-free.

How The Process Works

To decaffeinate coffee beans, the process relies on two concepts entirely, osmosis and solubility.

To get the decaffeination process started, hot water is used to soak green coffee beans in order to dissolve the caffeine. However, coffee contains other water-soluble substances other than caffeine. Sugars, as well as other chemical components, are what create the aromas and flavor that we love in coffee and they can dissolve in water as well.

After soaking the green beans, water from the initial round is run through a charcoal filter. The filter traps caffeine since it is a large molecule while the oils, sugars, and other chemical elements (aromas and flavor) pass through the filter and remain in the water. This creates what is referred to as “Green Coffee Extract.”

The green coffee extract-infused water is then used for soaking the next green bean batch. Since the other flavor elements are already contained in the Green Coffee Extract, these substances will not dissolve out of the beans, and the only thing that is removed is caffeine.

The video below from SwissWater goes over their process in more detail. Providing more information on the intricacies of the process and percentages of removal.

2. Carbon Dioxide Process

Carbon dioxide is in the second non-solvent based method for eliminating caffeine.

A scientist at New Plank Institute named Kurt Zosel developed the Carbon Dioxide Method. Instead of chemical solvents, it uses liquid CO2. It acts on the caffeine selectively, i.e., it only releases the alkaloid.

That is just a fancy way to say that CO2 is placed under high pressure and temperatures giving it liquid and gas properties. This supercritical, semi-liquid state makes a substance that is ideal for removing caffeine from coffee beans.

During the process, the water-soaked coffee beans are put into the extraction vessel, which is a stainless steel container. Then the extractor is sealed and liquid CO2 gets forced into the coffee at 1,000 psi in order to extract caffeine from the coffee

The CO2 works as a solvent and dissolves and draws the caffeine out of the coffee beans, which leaves the larger-molecule components that provide flavor behind. The caffeine-rich CO2 is then transferred to a different container referred to as the absorption chamber. The pressure is then released and CO2 is returned to its gaseous state, with the caffeine being left behind. This caffeine-free CO2 gas gets pumped back into the pressurized container to re-use later.

This process is expensive so it is mainly used for decaffeinating large quantities of less-exotic, commercial-grade coffee that are sold in grocery stores.

Solvent Based Methods

With solvent-based processes, caffeine is removed from coffee beans with help from a chemical solvent, like ethyl acetate or methylene chloride. In turn, the solvent-based processes are divided into methods that use them both directly and indirectly.

The direct method involves removing caffeine by directly soaking the coffee beans in the solvent. With the indirect method, the caffeine-rich water gets transferred into a separate container and then a solvent is used to treat it. The beans are never touched by the solvent.

Solvents Used in the Decaffeination Process

As previously mentioned, these methods use a solvent to decaffeinate coffee. A chemical solvent gets added either indirectly or directly to eliminate the caffeine.

Given the many health scares associated with early decaffeination efforts (such as benzene being a human carcinogen), ethyl acetate and methylene chloride are the preferred solvents.

1. Direct Solvent-Based Decaffeination Process

With this decaffeination method, the coffee beans are steamed for around 30 minutes to open up their pores. Once the coffee beans are ready to be receptive to a solvent, the beans are then rinsed repeatedly with either ethyl acetate or methylene chloride for around 10 hours to eliminate the caffeine. 

Usually, ethyl acetate is the solvent that is used in this method.

ethyl acetate formula
Formula for Ethyl Acetate

Then caffeine-laden solvent is drained away. The coffee beans are then steamed once again to eliminate any remaining solvent.

2. The Indirect Solvent-Based Process

Basically, the indirect method is a combination of the direct method and the Swiss Process. The indirect solvent-based method involves soaking the coffee beans in water that is nearly at boiling point for several hours. This extracts the caffeine in addition to other oils and flavor elements from the coffee beans.

Then the water is separated and transferred to a different tank. The beans are then washed for around 10 hours with either ethyl acetate or methylene chloride. The chemical solvent’s molecules bond selectively with the caffeine molecules. Then the resulting mixture is heated to evaporate the caffeine and solvent.

methylene chloride formula
Formula for Methylene Chloride

Finally, the coffee beans get reintroduced to the liquid in order to reabsorb most of the flavor elements and coffee oils.

In Europe, this is a very popular method, especially in Germany, and the primary solvent that is used is methylene chloride. Usually, if a process is not identified for a decaffeinated coffee, then it has been either treated by the indirect or direct solvent methods.

Why is Making Good Decaf Coffee So Hard?

Let’s begin by stating a fact that is rather sad: finding a good decaf coffee is an exception rather than being the norm. The reason for that stems from two major problems that are very hard to overcome.

First of all, as we have seen already, the decaffeination process has a tendency to damage many of the flavor compounds which contribute to a roasted coffee’s sensory character.

Second of all, it is very difficult to roast decaf coffee. The reason for that is unroasted, decaffeinated coffee beans begin as practically brown in color instead of green. That makes it hard for roasters to control the beans since they respond inconsistently to the heat that is applied to them throughout the roasting process.

They also contain less bound moisture content, and that causes them to roast faster. So, you must deal with a “green” unroasted bean that has a tendency to roast faster and darker than coffee beans that are not decaffeinated.

However, it’s not a completely lost cause. Given all that we have learned, this information can be used to ensure an improved decaf experience. Overall, the kind of roast you purchase will have more of an impact on its taste rather than the method used to decaffeinate the bean in the first place.

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