I often asked myself this question: how is coffee decaffeinated? After doing my research, I started to ask myself other questions: is decaffeinated coffee toxic? What is the environmental impact of decaffeination processes? If like me you like to take a deca from time to time, I think that knowing the processes used will interest you.
This study demonstrated that decaffeinated beverages still retain 1 to 2% (and sometimes even 20%) of the original caffeine content.
A little history
The first person who managed to extract pure caffeine from coffee was the chemist Friedlieb Ferdinand Runge in 1820. He did not consider it necessary to patent his process for extracting caffeine from coffee beans for marketing decaffeinated coffee. In truth he was especially interested in studying caffeine. Unfortunately he has not made great progress in the chemical properties of this molecule.
The first commercial decaffeination process was invented by the German merchant Ludwig Roselius in 1903 (patented in 1906). In 1903, Ludwig accidentally discovered this method of decaffeination. How? and his cargo of coffee beans soaked in seawater during any trip. His coffee has lost much of his caffeine without losing much taste.
The first industrial decaffeination processes involved steaming coffee beans, various acids / bases and benzene. This process is no longer used because benzene has carcinogenic properties.
Since then, other less toxic processes have been used.
Common characteristics of decaffeination
In all decaffeination processes, coffee is always decaffeinated and not roasted. The biggest challenge to the decaffeination process is to try to separate only the caffeine from the coffee beans while leaving the other chemicals at their original concentrations. It is not an easy task. Coffee contains a large number of chemicals that contribute to taste and aroma.
Since caffeine is a polar, water-soluble substance. As a result, we use water in all forms of decaffeination. However, water is not the best solution for decaffeination because it is not a selective solvent and therefore removes other soluble substances. Therefore, most decaffeination processes use a decaffeinizing agent such as methylene chloride, activated charcoal, CO2 or ethyl acetate.
Decaffeination process for coffee
There are several methods to decaffeinate coffee. This process is only performed on unroasted coffee. The coffee beans are steamed and rinsed with a solvent. This solvent extracts caffeine by not affecting (or little) the other components. The steps are repeated (8 to 12 times). That is, until the caffeine content meets the required standards. 97% caffeine eliminated according to the American standard and 99.9% eliminated by mass according to the EU standard.
Organic solvent processes
Solvents used in decaffeination
Given the many health warnings, we no longer use the first solvents. They are replaced by dichloromethane and ethyl acetate.
Dichloromethane is capable of selectively extracting caffeine and has a low boiling point. We use it in the United States of America. However, it is slightly toxic and carcinogenic. The residual solvent must therefore be less than 10 parts per million (ppm).
Ethyl acetate subsequently replaced dichloromethane. Ethyl acetate is also slightly toxic. Curiously, decaffeinated coffee with this solvent is sometimes marketed as “naturally decaffeinated”. The explanation found is simple. We can obtain ethyl acetate from a biological process (such as the fermentation of sugar cane).
Extraction with supercritical fluid
This approach uses CO2 as a supercritical material. This process is called “supercritical fluid extraction”.
Supercritical CO2 acts selectively on caffeine, releasing the alkaloid and nothing else. We place the coffee beans soaked in water in an extraction container. Then we seal the extractor and supercritical CO2 passes through the coffee at high pressures. This allows you to extract caffeine.
CO2 acts as a solvent for dissolving and removing caffeine from coffee beans, leaving behind larger aromatic components.
After this step, we transfer the caffeine-laden CO2 into an absorption chamber. The released pressure allows the CO2 to return to its gaseous state. As he evaporates, he leaves the caffeine behind him. Caffeine is removed using charcoal filters. Then, we recycle CO2. This method has the advantage of avoiding the use of potentially harmful substances. CO2-decaffeinated coffees are commercial-grade, less exotic coffees found in grocery stores.
Extraction with water
Coffee beans dip in hot water. The water used contains other components that contribute to the coffee taste. After about 10 hours of treatment, the water passes through an activated carbon that retains caffeine. Then, the water is put back with the coffee then the water is evaporated. This approach leaves the coffee with a good aroma.
One of the main sources of the article is this book.