It’s no wonder that decaf coffee has become more popular as coffee drinkers are becoming increasingly health conscious and informed about the effects of excess caffeine consumption. Supporting this trend, a wide range of high-quality decaffeinated coffee varietals have exploded onto the market over the past 10 years, bringing coffee lovers decaf that can stand toe-to-toe with caffeinated coffees.
With so much energy focused on understanding and appreciating the unique characteristics of coffee from different origins, we wanted to take a step back to explain the science of how modern coffee decaffeination processes remove caffeine without damaging the delicate flavors that make each coffee unique.
How is caffeine removed to produce decaffeinated coffee? In this article we explain the “hows” and “whys” of the three main decaffeination methods in use today: water processes like the Swiss Water® process and Mountain Water process, natural solvent decaffeination, and CO2 (carbon dioxide) decaffeination. If you’re short on time, skip down to the summary at the end of this article for a quick take on these three methods.
What is decaffeinated coffee?
Decaffeinated coffee, or “decaf”, is coffee which has had nearly all of its natural caffeine content removed. In the U.S., USDA regulations require that at least 97% of the caffeine is removed during the decaffeination process, and some companies report even lower levels of caffeine in their decaffeinated beans. In practice, this means that the caffeine content in a large cup of decaf coffee is at least 15 times less than in one bar of dark chocolate.
The decaffeination methods in use today all selectively remove caffeine while preserving the other components that give coffee its rich and unique flavor.
How is coffee decaffeinated?
There are three main decaffeination methods in use today:
- Water processes like the Swiss Water® process and Mountain Water process
- Natural solvent processes
- CO2 (carbon dioxide) processes
All coffee is decaffeinated in its green, unroasted state. The first step in all decaffeination processes is to hydrate the green coffee beans with water. Re-hydrating the beans is important because it allows the cells and pores of the coffee bean to expand and release caffeine in subsequent steps, which vary depending on the decaffeination method.
Let’s start by discussing the Swiss Water® process.
Problems Faced by Traditional Water Processes:
Water processed decaf coffee first became available in the 1970’s, but the process often produced dull tasting coffee because water soluble flavor components were also removed from the coffee bean during decaffeination.
The original water process worked by washing green coffee beans in water to extract the caffeine. The water, containing caffeine and flavor compounds, was then passed through filters to remove the caffeine, and then condensed and returned to the beans to add back the flavor. The issue with this technique is that extracted coffee flavors are lost at each step of the process, especially during filtration to remove the caffeine.
The Swiss Water® Process
In the late 1980’s, the Swiss Water® process introduced two innovations that eliminated this problem and produced full-flavor decaf coffee using only water without the aid of any other solvents. The first innovation is “green coffee extract”, or “GCE”. Green coffee extract is produced before the first batch of beans is decaffeinated by creating a strong “tea” from green coffee beans. After extracting flavor compounds and caffeine from the green coffee beans, the GCE is passed through a filter that removes the caffeine. The finished GCE contains all of the flavor compounds from the green coffee without the caffeine. The initial batch of beans used to produce the GCE is discarded, and the GCE is used to decaffeinate subsequent batches of coffee beans.
Since the GCE is already fully saturated with soluble coffee compounds, the resulting concentration gradient prevents the flavor components from being extracted during the decaffeination process. However, since the GCE contains no caffeine, it readily extracts caffeine from the green coffee. The result is that only caffeine is extracted from the coffee, leaving the flavor components in the bean.
After the caffeine is extracted into the GCE, the GCE is passed through a filter that selectively removes the caffeine molecules, allowing the GCE to be used to decaffeinate many batches of coffee. Check out this two-minute video for a quick overview of the Swiss Water® process.
The second innovation Swiss Water introduced is the concept of “pre-loading” the caffeine adsorption filter with soluble coffee compounds. This prevents the filter from extracting other components from the GCE so that only caffeine is removed. You can read more about this process in the patent here.
Today, all Swiss Water® process coffee is decaffeinated in the Swiss Water company’s state-of-the-art Canadian facility in British Columbia.
How much caffeine is left in Swiss Water® process coffee?
Coffee decaffeinated using the Swiss Water process is 99.9% caffeine free. The Swiss Water company has been instrumental in bringing exciting new varietals to decaf coffee which were previously underrepresented. Cupper has a wide selection of Swiss Water processed coffee, so you’ll be sure to find your favorite roast and origin represented.
Mountain Water Process
The Mountain Water process is a trade name for Descamex’s water decaffeination process. Descamex uses a technique similar to the Swiss Water® process to remove caffeine using water without extracting flavor compounds from the coffee. Dexcamex’s facility is located in Mexico and uses fresh spring water from the Pico de Orizba mountain to decaffeinate its beans.
Natural Solvent Processes
Solvent processes use an organic solvent to extract caffeine from green coffee while preserving the flavor components that give the bean its taste and character. Historically two main solvents have been used to decaffeinate coffee, methylene chloride, and ethyl acetate. Both solvents are considered safe by the FDA and approved for use to decaffeinate coffee.
Types of Solvents
Ethyl acetate (EA) is a naturally occurring ester of ethanol and acetic acid (vinegar) which is naturally found in fruits like bananas, apples, and pears, as well as fermented products like beer and wine. Ethyl acetate has been approved for decaffeination by the FDA since 1982, with no limit set on the residual that can remain in coffee since it is considered safe for human consumption and is completely digestible. However, coffee decaffeinated using ethyl acetate contains only a trace amount of residual due to the washing and drying process used to prepare the beans. Any remaining residual is removed when the coffee is roasted thanks to ethyl acetate’s low boiling point. Due to its safety and availability, nearly all solvent decaffeinated coffee produced today uses ethyl acetate.
All of the EA coffee we sell is labeled “sugarcane process” since it is decaffeinated using ethyl acetate derived naturally from sugarcane by fermenting molasses. This process is common in Colombia where sugarcane is abundant since it is a cost-effective way to produce high-quality decaf coffee.
Methylene chloride is an organic solvent produced by some types of algae and used to prepare flavorings in the food industry. FDA regulations require that decaffeinated coffee contains no more than 10 ppm (parts per million) methylene chloride, but most coffee decaffeinated with methylene chloride only contains 2 to 3 ppm. Since methylene chloride boils at 103 °F, essentially none remains after the coffee is roasted.
Even though the FDA considers this methylene chloride safe to use, some coffee drinkers have reservations. At Cupper, we don’t sell any decaf processed with methylene chloride, so you can pick your favorite roast without worrying about the decaffeination process. There are also concerns that methylene chloride contributes to ozone depletion, which another great reason to choose alternatives.
How are solvents used to decaffeinate coffee?
So far, we have discussed the types of solvents used, but how are the beans decaffeinated? There are two main processes in use today which we will discuss further below.
Direct Solvent Process
There are two main solvent decaffeination methods in use today, the direct process and the indirect process. In the direct process, green coffee beans are steamed or soaked in water to increase their moisture content and open the pores of the bean to allow the solvent to extract the caffeine. This method is called the “direct” process since the green coffee beans are washed directly in the solvent, which selectively removes the caffeine without dissolving the flavor components. After several hours of gentle washing the beans are rinsed with water and dried under a vacuum to boil off any residual solvent.
Indirect Solvent Process
In the indirect solvent process, caffeine and other components of the coffee are first extracted in water. The extracted water is then separated from the coffee beans and washed using a solvent which is immiscible and does not mix with the water. The solvent extracts the caffeine from the water, leaving the other coffee components and flavors in the water solution. This water solution is separated from the solvent and concentrated with heat under a vacuum so that it boils at a lower temperature. At the same time, the coffee beans are dried to reduce their moisture content so that they can re-absorb the concentrated coffee water solution. The result is clean decaffeinated coffee that preserves most of the original flavor of the bean.
Regardless of which process is used, the amount of residual solvent remaining is typically than 5 ppm, and effectively zero once the beans have been roasted.
CO2 (carbon dioxide) processes
This decaffeination method uses supercritical CO2, carbon dioxide that has been compressed into liquid form, to remove caffeine from the green coffee bean. The CO2 is considered one of the most selective processes to remove caffeine without affecting the other components of the coffee. Under immense pressure, CO2 becomes a liquid and is nearly as dense as water, but it is much less viscous, allowing it to easily penetrate the coffee beans to dissolve away caffeine. Due to the highly selective removal of caffeine, the flavor and properties of CO2 decaf are very similar to caffeinated coffee.
Unfortunately, the setup and operational costs of a CO2 decaffeination plant are high, meaning that these facilities need to process several thousand tons of coffee per year to remain economical. For this reason, CO2 decaffeination is primarily used to process large batches of commercial grade coffee. However, some specialty grade coffee is decaffeinated using the CO2 process.
If you’ve read this far, congratulations on your new decaf knowledge. If you skipped to here from the introduction, no worries, we’ll fill you in on what you missed.
To recap, most coffee today is decaffeinated using one of these three methods:
- Water processes like the Swiss Water® process or Mountain Water process
- Natural solvent processes
- These processes use naturally occurring ethyl acetate (also found in fruits and wine) to extract caffeine from green coffee.
- Since It is a naturally-occurring chemical, you’ll often see coffee beans decaffeinated with this method labeled as naturally decaffeinated.
Supercritical CO2 (carbon dioxide) processes
- This method uses liquified carbon dioxide to dissolve caffeine from the coffee beans without extracting flavor components or leaving any residual on the coffee.
All three of these methods are designed to remove as much caffeine as possible while preserving the unique flavor and characteristics of the coffee bean. In the U.S., the USDA regulates that “decaf” coffee must have at least 97% of the caffeine content removed, with many decaf producers reporting that their decaf coffee is 99.9% caffeine free.
Roasting decaffeinated coffee is both art and science, and it’s generally trickier to roast decaf than caffeinated coffee beans. All of the decaf at Cupper is carefully handpicked from the nation’s best roasters that put a lot of love and care into their decaf roasting profile. Check out our great selection of decaf and find your next cup.
Whichever process your favorite decaf uses, modern decaffeination methods ensure you’re enjoying a healthy, delicious, and caffeine free cup!