In 1820, a German chemist called Friedlieb Ferdinand Runge, discovered how to extract the caffeine from the coffee beans. Then, in 1905, the German Ludwig Roselius invented the first process for decaffeinating coffee. His method used benzene, a highly flammable liquid that nowadays is been replaced with non-toxic solvent.
Is it safe to drink decaf coffee?
The decaffeination process usually removes 97 to 99% percent of caffeine from the beans.
When roasted, the beans lost any chemical residual (they are volatile compound) that still could be inside.
About the Process
There are basically three ways to extract the caffeine from the beans:
- Solvent Process
- Swiss Water Process (SWP)
- Carbon Dioxide Process
Regardless of the type of solvent we use (mostly methylene chloride or ethyl acetate), the process is the same. The solvent process is divided in two methods: the direct and the indirect one. In the direct method the green beans are soaked in hot water increasing the surface area of the beans to let the solvent penetrate easily to extract the caffeine. The solvent (especially the methylene chloride) easily bonds with the molecules of hydrogen of the caffeine obtaining a high-quality extraction; after many hours (up to ten) of rinsing, the beans are steamed another time to remove any residuals.
In the indirect method the beans are rinsed by the water removing the caffeine; what we obtain is then separated from the beans (the beans are never get in contact with the solvent) and put in another tank and treated with the solvent. The mixture is then warmed again to evaporate the solvent and the caffeine. And finally, the beans are re-added to the mixture to reabsorb the flavours.
Swiss Water Process (SWP)
This process was invented in 1930s in Switzerland and then introduced in 1988 in a facility in Vancouver. This is the only method that has been both certified organic and kosher. First, there’s no solvent required: the green beans are soaked in hot water to dissolve the caffeine. The water is then filtered with a charcoal filter with large pores that only hold caffeine molecules allowing all the oil and flavour compounds to pass through. Then the beans are discarded and another batch of beans are ready to be decaffeinated by the water that was previously filtered by the charcoal filter. At this point, the water is saturated of its flavour compounds so it can only extract the caffeine molecules. So, the result is a second batch of decaffeinated coffee full of flavours. This is the process mostly preferred even if it leads to wastage.
Carbon Dioxide process
This method was discovered by the scientist Kurt Zosel at the Max Planck Institute in 1967, using CO2 instead of any solvents. In 1988 a German company called CR3 patented a process called Natural Liquid Carbon Dioxide Decaffeination Process. In this method the green beans are soaked in the extraction vessel, a stainless-steel container. In this container the CO2 is forced at high pressures (around 1000 pounds per square inch) that give it both gas and liquid status allowing to extract caffeine. Liquid CO2 extracts the caffeine leaving the flavours behind. Then the caffeine is put in another container called the absorption chamber where the pressure is released (now the CO2 is in gas status) leaving the caffeine behind. This process doesn’t waste too much as the Swiss method does.
Regardless the process, all the beans are dried: the moisture is removed until it reaches the ideal content, ready to be roasted.