How is Coffee Decaffeinated?

how is coffee DecaffeinatedFor coffee lovers that don’t always need the maximum rush from caffeine, there are different options available from lower caffeine to decaffeinated. If you’re like us at Gathering Grounds, and always want to know how they make something, then you’ll enjoy reading about how decaffeinated coffee is made from your favorite coffee beans.

Just over 100 years ago, the first process of removing caffeine was developed by Ludwig Roselius in 1905. The method used the potentially toxic chemical called Benzene to strip the caffeine from green coffee beans. Thankfully that method is longer called for, and we have three much more simple and less toxic methods to remove caffeine. All three are similar with roasting or moistening green coffee beans and then using a temperature between 160 and 210 degrees Fahrenheit (70 to 100 degrees Celsius).

Method 1 – Water Processing

The first method that is used to create decaffeinated coffee involves just plain water. Water is used as a solvent inside eight to twelve vessels that contain green coffee beans at each level of the process. Think of each vessel as a step in the process from beginning to end, and when one step finishes, the beans from that vessel are moved to the next step. A reduced caffeine mixture of water and green-coffee extract is circulated around the green coffee beans within the extraction vessel to separate the caffeine from the beans. Oils in the coffee extract aid in the decaffeination process.

After a certain amount of time, the vessel and contents are emptied, and then rinsed and dried. The caffeine-laden extract that was taken from the vessel containing the freshest green coffee beans in step 1 is passed through activated charcoal that absorbs the caffeine. This charcoal will have been treated with a carbohydrate (typically sucrose) that helps it absorb caffeine without removing other compounds that add to the base coffee flavor. The lower caffeine extract removed from the vessel is then reused to begin the process again with a fresh amount of green beans.

The water process is considered natural, as it doesn’t involve synthetic chemicals. You may find packages labeled as ‘naturally decaffeinated’ that have used this process. The water solvent processing method typically removes 94% – 96% of the original caffeine.

Method 2 – Liquid Solvents

The second common decaffeination method is using a direct solvent (different than water) in the process. This technique often uses methylene chloride (used mostly throughout Europe), coffee oil or ethyl acetate to dissolve the caffeine and extract it from the green coffee beans. Ethyl acetate is found naturally in fruits and vegetables such as bananas, apples and coffee beans. The direct liquid solvent is dispersed through moist green coffee beans and this removes a small amount of the caffeine. The liquid solvent is then captured in an evaporation process and the beans are washed with water. Residue of the used solvent is removed from the coffee down to minimal levels by steaming the beans.

This process is usually done with large batches of coffee beans as the liquid solvents are easier to target at the caffeine than the charcoal is from method #1. The liquid solvent is used several times to reduce the caffeine amount to the desired level and will typically not affect the non-caffeine solids in the beans that contribute to the coffee flavor. Method #2 will usually extract 96% – 97% of the original caffeine. This processing method can also be labeled as ‘naturally decaffeinated’ when ethyl acetate is used because it is a product from naturally grown fruits and vegetables instead of a synthetic solvent.

Method 3 – High Pressure Carbon Dioxide

The third common method for decaffeination uses carbon dioxide in a supercritical phase. The vessels involved are high-pressure units that operate at roughly 250 to 300 times atmospheric pressure. They circulate the supercritical carbon dioxide through moistened green coffee beans. The supercritical part happens at the high pressures used to enhance the usefulness of carbon dioxide as a solvent. Supercritical carbon dioxide takes on a density of a liquid, but its viscosity and diffusivity are similar to those of a gas. These traits make supercritical carbon dioxide a commonly solvent because it has a lower pressure critical point and it is abundant in nature. The caffeine-laden carbon dioxide leaving the extraction vessel is channeled through a bed of activated charcoal or through a water bath tower to absorb the caffeine. The carbon dioxide is then circulated back to the extraction vessel to start the same process over on a new set of green coffee beans.

One of the drawbacks of using this method is the initial cost of the equipment. It’s very expensive on the front end, but also has one of the better yields as a result. The process using supercritical carbon dioxide can extract 96% – 98% of the original caffeine in the green coffee beans.

Out of those three methods, which would you choose? After looking at a few coffee brand labels, they don’t tell you typically what method they use. Some brands just list the coffee as decaffeinated or naturally decaffeinated, but specifically list the method as part of the details in their advertising. Most labels will list the amount of caffeine removed or the amount left in the product, and judging how close they all are in percentage removed it really may leave you just as inquisitive in the end.

If you’ve ever wondered just how popular decaffinated coffee has become, know that it’s currently listed at 12% of the world-wide volume of coffee consumption. The total coffee industry is huge, and just the United States industry is valued in the neighborhood of $19 billion annually. Unless you have a known allergen to a solvent used in any of the methods to decaffeinate coffee beans, or your government has a ban on any of the materials or methods, you will probably never know the exact process. Each brand has a tightly guarded secret process specific to their flavoring that will continue to stay a secret.

Brian Mounts

Head blogger, editor, and owner of "Top Off My Coffee", a website that has been educating readers about coffee brewing techniques and equipment since 2012.

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