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3 methods for decaffeinating coffee


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When you enjoy a cup of decaffeinated coffee, have you ever wondered how caffeine is extracted from coffee beans? After doing my own research, I began to ask myself other questions: is decaffeinated coffee safe to drink? What is the environmental impact of decaffeination methods? In this article, we take an in-depth look at the fascinating process of decaffeinating coffee. Discover the different techniques used to remove caffeine while preserving coffee’s distinctive flavors and aromas. Get ready to discover the secrets of decaffeination.

Despite the decaffeination process, a small amount of caffeine may remain in decaffeinated drinks. According to a recent study, these beverages may still contain between 1% and 2% of their original caffeine content. In the most extreme cases, this can be as much as 20%.

A little history

Chemist Friedlieb Ferdinand Runge succeeded in extracting pure caffeine from coffee in 1820. However, he did not patent his process to market decaffeinated coffee. In fact, his main aim was to study the molecule. However, he didn’t make any great advances in understanding its chemical properties.

The first commercial decaffeination process was invented by German merchant Ludwig Roselius in 1903 (patented in 1906). Ludwig discovered the method by chance when his cargo of beans was soaked in seawater during a voyage. His coffee had lost much of its caffeine without losing much of its taste.

As a patron of the arts, he supported a number of leading artists, including Paula Modersohn-Becker and Bernhard Hoetger.

Ludwig discovered this method by chance. His grain freight was soaked in seawater during an entire voyage. However, this process is no longer used due to the carcinogenic properties of benzene. Since then, other less toxic methods have been developed to extract caffeine from coffee beans.

Shared characteristics of decaffeination methods

In all decaffeination processes, the coffee beans are decaffeinated before being roasted. The main challenge of decaffeination is to separate only the caffeine from the coffee beans. The aim is to preserve the other chemical compounds in their original concentrations. This proves to be a complex task. Coffee contains a large number of chemical compounds that contribute to its distinctive taste and aroma.

Green coffee beans
Coffee is decaffeinated before roasting, when the beans are still green.

Caffeine is a polar, water-soluble substance, which means that water is used in all decaffeination methods. However, water is not the ideal solvent for decaffeination. It is not selective and also removes other soluble substances. This is why most decaffeination processes use decaffeinating agents. These may include methylene chloride, activated carbon, CO2 or ethyl acetate, to achieve a more precise result.

The different methods of coffee decaffeination

There are several methods for decaffeinating coffee, all performed on unroasted coffee beans. The beans are first steamed, then rinsed with a solvent that extracts the caffeine while preserving the other components. This process is repeated 8 to 12 times until the caffeine content reaches the required standards, i.e. 97% caffeine removal according to the US standard and 99.9% by mass according to the EU standard.

Decaffeination methods using organic solvents

Solvents used in decaffeination

Due to health concerns, the first solvents used for decaffeination were replaced by dichloromethane and ethyl acetate. Dichloromethane, used in the USA, is capable of selectively extracting caffeine and has a low boiling point. However, it is slightly toxic and carcinogenic, so the amount of residual solvent must be less than 10 parts per million (ppm). Ethyl acetate, also slightly toxic, subsequently replaced dichloromethane.

Curiously, coffee decaffeinated with this solvent is sometimes marketed as “naturally decaffeinated”, as ethyl acetate can be obtained from a biological process such as sugarcane fermentation.

Supercritical fluid decaffeination

Supercritical fluid extraction usesCO2 in a supercritical state to act selectively on caffeine, releasing only this alkaloid. Water-soaked coffee beans are placed in a sealed extraction vessel, where supercriticalCO2 passes through the coffee at high pressures to extract the caffeine. TheCO2 acts as a solvent to dissolve and remove the caffeine from the coffee beans, while preserving the larger aromatic components. The caffeine-ladenCO2 is then transferred to an absorption chamber where pressure is released, allowing theCO2 to return to its gaseous state and leave the caffeine behind. The caffeine is removed using carbon filters, and theCO2 is recycled. This process has the advantage of avoiding the use of potentially harmful substances, and produces less exotic, commercial-quality decaffeinated coffees available in grocery stores.

Decaffeinate with water

In this method, the coffee beans are soaked in hot water containing other components that contribute to the coffee’s taste. After around 10 hours of treatment, the water is filtered through activated carbon, which retains the caffeine. The water is then brought back into contact with the coffee and evaporated, leaving behind a coffee with a good aroma.

Read our history articles here.


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