How Caffeine Is Removed from Coffee

published Jul 2, 2015
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(Image credit: Leela Cyd)

Most of us are addicted to caffeine. We drink it every morning out of habit, but also to give us a much-needed boost to get us going or to help us face the day. Caffeine is a stimulant targeting the central nervous system and it does a really good job of combating drowsiness and helping us feel more awake.

However, past a certain time in the day, many of us avoid caffeine for fear it may lead to a sleepless, restless night, so we turn to decaf. Let’s explore some of the ways that caffeine is removed from coffee.

A Guide to the Many Types of Caffeine Extraction

In order to remove the caffeine from coffee beans, the beans are washed in a solvent (a liquid capable of dissolving substances), transferring the caffeine from bean to liquid in a process known as extraction.

To extract caffeine from whole coffee beans, the following solvents 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 are 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. That decaffeinated green coffee extract is then used 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 flavours 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.

Which Decaffeination Methods Are “Natural”?

The word “natural” may be used to describe the decaffeination process using water, and printed on the labels of coffees that were decaffeinated with water, but this “natural” descriptor can also appear on bags of beans decaffeinated with the organic solvent ethyl acetate instead of dichloromethane. That’s because some fruits and vegetables actually naturally produce ethyl acetate in small amounts, so ethyl acetate is sometimes categorized as a “natural” solvent. Of course, given the quantities required to wash and extract the caffeine from large amounts of coffee beans, it’s unlikely that the ethyl acetate is from a natural source, and is therefore more likely synthetic.

In general, I hesitate to trust when something is labelled as “natural.” If you are worried about the organic solvents used during the extraction process, your best bet is to seek out decaf coffees that clearly state that they used a Swiss Water Process.

Are you a decaf coffee drinker? Do you switch to decaf at the end of the day, or do you prefer to generally avoid caffeine?