The Decaffeination of Coffee

May 10, 2019

Whether it’s cars lined up at the local coffee shop or the coffee maker dispensing morning joe in the kitchen, it seems like everyone wants a jolt. But what if you’re sensitive to the stimulating effects of caffeine? Can you still enjoy the hot, roasted goodness of coffee? The answer is: yes! Decaf coffee, processed to eliminate the caffeine, has been around for over a 100 years and is a popular product in its own right.9

The process of decaffeination originated in Germany at the turn of the 20th century and by 1908 had made its way to the United States. Prior to World War II, the process involved using solvents—like trichlorethylene, chloroform or benzene—to extract caffeine out of the raw coffee beans.1 Since then, the decaffeination process has evolved to use different techniques and fewer chemical solvents. These advancements in decaffeination technology help preserve more coffee flavor so that coffee drinkers can find increased enjoyment in drinking decaf. Today there are three common ways to extract caffeine from raw coffee beans: Swiss water processing, the use of solvents, and carbon dioxide extraction.2

The Swiss Water Process

The Swiss water processing method was developed in Switzerland in the late 1970s.2 This process involves adding raw coffee beans to hot water where osmosis extracts the caffeine and flavor notes from the beans into the water. The water is then run through a carbon filter to remove the caffeine. The beans are half-dried and sprayed with the water, which still contains the flavor of coffee, so that the taste—but not the caffeine—of the beans is restored. 2, 3

Solvents

Another method of caffeine extraction is the use of organic solvents, or liquids added to a solution that will bind to, and remove, the caffeine molecule. This process can be completed by either a direct method or an indirect method. In the direct method, the raw coffee beans are steamed under high temperatures and treated with solvents to remove the caffeine. The decaffeinated beans are then heated to remove any excess solvent and moisture that has been absorbed into them by the decaffeination process.2

In the indirect method, coffee beans are steeped in hot water to dissolve the caffeine. During this process, the flavor notes also escape the beans and get dissolved into the water. The water is then separated from the beans and treated with a solvent that bonds with the caffeine. The caffeine is evaporated away from the water, leaving only the flavor notes, which are added back into the beans. Common solvents used to decaffeinate coffee are methyl chloride and ethyl acetate.2

Carbon Dioxide Extraction

The last method of decaffeination was created in the 1970s and involves the use of carbon dioxide. In general, once the raw coffee beans are soaked in water and the desired moisture content in the beans is achieved, carbon dioxide is added to the beans and water under high temperatures and pressure. The carbon dioxide binds to the caffeine molecule and removes it from the bean. The caffeine-laden carbon dioxide is then mixed with water, where the water carries away the caffeine and the carbon dioxide is recycled to be used again. The decaffeinated beans are subsequently dried, and the residual carbon dioxide is removed from the beans. 2, 4 This decaffeination process produces a higher-quality product that preserves more coffee flavor than the other methods.5 Due to the higher costs of this process, it is commonly used in the decaffeination of commercial-grade coffee—that is, coffee packaged in larger plants by widely recognized brands.2

Caffeine Amounts in Decaf

To be considered decaffeinated, a threshold of no more than 0.10 percent of caffeine on a dry basis must be achieved, according to the USDA.6 This translates to a brewed coffee that is approximately 97 percent caffeine-free, but the exact amount may vary. While this is a substantial reduction in caffeine, and should help avoid many of its stimulating effects, it is important to keep in mind that a tiny bit of caffeine remains even in decaf varieties. To put it in perspective, a small cup of coffee-house coffee contains around 230 mg of caffeine, whereas its decaffeinated counterpart can contain about 20 mg.7,8 Again, the exact amount of caffeine remaining in your brewed decaf will vary slightly from batch to batch.

Sources

  1. Sivitz, Michael. Chap. 19 in Coffee Processing Technology, 2. The Avi Publishing Company, 1963. 207–215.
  2. Ramalakshmi and B. Raghavan. “Caffeine in Coffee: Its Removal. Why and How?” Critical Reviews in Food Science and Nutrition. (1999): 441–446.
  3. Mazzafera, Paulo & Baumann, Thomas & Massao Shimizu, Milton & Silvarolla, Bernadete. “Decaf and the Steeplechase Towards Decaffito—the Coffee from Caffeine-Free Arabica Plants.” Tropical Plant Biology. (2009): 63–76.
  4. Zosel, Kurt. “Process for the decaffeination of coffee.” https://patents.google.com/patent/US4260639A/en.
  5. Farah, Adriana. Chap. 2 in Coffee: Emerging Health Effects and Disease Prevention, First Edition. Blackwell Publishing Ltd., 2012.
  6. United States Department of Agriculture. “Commercial Item Description: Coffee.” https://www.ams.usda.gov/sites/default/files/media/CID%20Coffee.pdf.
  7. Starbucks Coffee Company. https://www.starbucks.com/menu/drinks/brewed-coffee/decaf-pike-place-roast.
  8. Panera Bread. https://www.panerabread.com/en-us/menu-categories/drinks.html.
  9. “Decaffeinated coffee per capita consumption in the United States from 2011 to 2018.” https://www.statista.com/statistics/456356/us-per-capita-consumption-of-decaffeinated-coffee/.