How Is Caffeine Removed from Coffee?
How Is Caffeine Removed from Coffee? In order to remove the caffeine from coffee beans, the beans are washed in a liquid capable of dissolving substances, transferring the caffeine from bean to liquid in a process known as extraction.
Caffeine is removed from coffee with the aid of certain chemicals. Caffeine is a substance that acts as a natural stimulant. Decaffeinated coffees are prepared for people who are sensitive to the caffeine in regular coffee.
To remove most of coffee’s caffeine, green coffee beans are steamed to swell their cells. The peanut-size beans are then soaked in a special solvent that flushes out about 97 percent of their caffeine.
The decaffeinated beans are then thoroughly rinsed and dried, and the dried beans, like regular coffee beans, are roasted and ground. To extract caffeine from whole coffee beans, the following can be used:
Water Extraction: The process to remove caffeine from coffee beans using water was first developed in Switzerland in the 1930s, but was only trademarked as the Swiss Water Process in the ’80s by a company in Vancouver, British Columbia.
In the Swiss Water Process, a batch of beans is washed in very hot water to extract the caffeine and other water-soluble compounds from the beans. The beans are discarded, while the water is filtered to remove the caffeine, yielding a caffeine-free green coffee extract. The decaffeinated green coffee extract is then reused to wash another batch of coffee beans.
Since the green coffee extract is already loaded with the water-soluble extracts of the coffee beans, this time, only the caffeine is extracted from the new set of beans, without losing any of the flavors and oils from the beans. The washing step is repeated until most of the caffeine has been extracted from the beans.
Organic Solvent (Direct Method) Extraction: The beans are moistened or steamed to open their pores, then washed over and over with an organic solvent, like dichloromethane (methylene chloride), which extracts the caffeine from the beans. When the beans are relatively free of caffeine, they are then washed with copious amounts of water and dried to remove residual solvent.
Since the organic solvents used to extract the caffeine from the beans are fairly volatile (the boiling point of dichloromethane is 40ºC to 103ºF), only trace amounts of solvent remain after the beans are dried. Furthermore, since the beans are roasted later, residual solvent should not pose a health threat.
Organic Solvent (Indirect Method) Extraction: The beans are washed with copious amounts of water to extract the coffee and other water-soluble compounds, then that coffee solution is mixed with dichloromethane to extract the caffeine from the water.
The caffeine transfers over to the dichloromethane, leaving the coffee flavors and other compounds in the water. The water is then mixed back with the beans and left for several hours to transfer back the coffee flavors and other compounds to the beans.
Supercritical Carbon Dioxide Extraction: For this one, you will need to recall that carbon dioxide is a gas at atmospheric pressure and temperature, but if you increase the pressure and temperature, carbon dioxide gas can transform into a supercritical liquid (sort of like a cross between a liquid and a gas).
And just like with solvents, the coffee beans can be washed with supercritical liquid carbon dioxide to extract the caffeine from them. The supercritical carbon dioxide can be passed through filters to remove the extracted caffeine and then recycled and reused to decaffeinate another batch of beans.