The four ways of decaffeinating coffee
In 1903 the German coffee merchant Ludwig Roselius invented the first ever (successful) decaffeination process, known as the Roselius process. We can’t know for sure, but legend has it that his quest for decaffeinated coffee guided by his belief that overconsumption of coffee had been the reason for his father’s passing.
Back in those days the green coffee beans were first steamed with a saltwater solution (brine). When this was done benzene was used as a solvent to remove the caffeine. In modern times we now know that Benzene can lead to serious health risks. Consuming it might lead to cancer in blood-forming organs such as leukemia, lymphoma, and multiple myeloma. Hence, why this method is no longer used.
Today there are four major processes used for decaffeination:
- Swiss Water Process,
- Carbon Dioxide Process.
The solvent based processes use some kind of a chemical solvent to remove the caffeine from the beans.
The first thing to understand about coffee is that it’s made up of around 1,000 chemical components that contribute to its taste and aroma. This is what makes it incredibly difficult to extract only the caffeine without altering the taste of the coffee. Water is applied during all decaffeination methods, but if it is used without some other decaffeinating agent, it can remove over soluble substances from the beans, like for example proteins and sugars, which could then alter the taste of the coffee. This is why it is easier and cheaper to remove caffeine with the help of some kind of chemical solvent. But easier and cheaper is not always better. Unfortunately good tasting decaf is the exception not the norm both due to the difficult process and also because roasting decaffeinated beans take a lot skill which we will discuss further at the end of this article.
When decaffeinating using the Direct-Solvent Process you allow the beans to come in direct contact with the chemical as to remove the caffeine. The process entails steaming the beans for about 30 minutes to release the caffeine and allow the pores to open up and become more responsive to the solvent. The next step is then to rinse them repeatedly for the next ten hours in either ethyl acetate or methylene chloride to bind the caffeine away from the beans. It is this last step that might raise some eyebrows and make people less inclined to drink decaf coffee that has been processed using the direct-solvent process.
Now the second method in the solvent-based category is the Indirect-solvent process to decaffeinate coffee beans. In this process the beans are soaked in hot water until the water absorbs the caffeine and all the other components in the bean. It is then transferred to another bath where is it treated with a solvent. During this part of the process, the solvent consumes only the caffeine with the other component remaining in the water and the solvent in then skimmed of the top of the water. The solvent is therefor only in contact with the caffeine and not with the coffee bean itself. The last step is then to return the “flavour-laden” water to the bath containing the beans where the coffee beans reabsorb the remaining components from the water.
Now, the third and our personal favourite is the Swiss Water Process. During the decaffeination process there are no chemicals involved, neither directly nor indirectly. This process has been around since 1933 but didn’t become a commercially viable process for another 55 years. It was only in 1988 that the Swiss Water Decaf became publicly know way of decaffeinating coffee.
The process involves steaming the beans to release the caffeine. The next step is to soak the beans in water that has been oversaturated with coffee compounds and through this the caffeine is then extracted in the water. The clever thing about this is that water can only hold a limited amount of flavour compounds, so when soaking the coffee in water that’s already oversaturated the added batch of coffee won’t release the flavour compounds, but the caffeine will, however, be released. The next step is for the water to go through and activated charcoal filter which will then capture the larger caffeine molecules but oil and flavour molecules that are far smaller will flow through. The final step is then to allow a slow drying phase and the result is decaffeination will still keeping the coffee flavours intact.
The final and recent decaffeination process is the CO2 method. This method uses carbon dioxide to remove the caffeine from the beans in the decaffeination process. Just like the other decaffeination processes the CO2 method starts with the green coffee beans being soaked in water. They are then placed in a stainless-steel tank (known as an “extraction vessel”). The vessel is then sealed, and CO2 is applied to the coffee at 1,000 pounds of pressure per square inch, this is done to extract the caffeine. The brilliant thing about this process is that the solvent only dissolves and extracts the caffeine out of the coffee beans, leaving the flavour molecules intact. The CO2, which is now filled with caffeine is then moved to the absorption container where the pressure is released, and the CO2 returns to its gaseous state and only the caffeine remains. The CO2 can be used again and is stored back in a pressurized thank until the next decaffeination procedure takes place.