Depending on the type of bean, brewing method, and amount of coffee used, a five ounce cup of non-decaffeinated coffee will contain from 70 - 155 milligrams of caffeine. (Based on its review of medical studies, the Institute of Food Technologists notes that moderate amounts of coffee - less than 600 milligrams a day - are not considered harmful to the average healthy adult.)

A coffee must have at least 97% of its caffeine removed to qualify as decaffeinated in the United States. Each five-ounce cup of decaffeinated coffee, therefore, contains less than 5 milligrams of caffeine.

Decaffeinated coffees tend to cost more than their non-caffeinated counterparts because of the additional labor, equipment, and material expenses required for caffeine removal. Coffee beans are decaffeinated before they are roasted, when the process can be done more cost effectively and with the least effect on the beans' flavor.

Drinkers of decaffeinated coffee can choose from a wide variety of unblended, blended, and flavored coffees with little sacrifice to flavor. Since the introduction of decaffeinated coffee to the United States just before World War I, the coffee industry has developed several methods to remove caffeine with a minimal loss of flavor and quality in the brewed product.

There are basically two methods of decaffeination: direct and indirect contact. In the first, the beans come directly in contact with the decaffeinating agents, after being softened by steam.

In the latter method, a water/coffee solution is normally used to draw off the caffeine; after being separated from the beans, the solution containing the caffeine is then treated with a decaffeinating agent.

In both methods, the agent is removed from the final product.

Agents of Decaffeination
The following agents are commonly used in decaffeinating coffee:

1. Methylene Chloride
In the direct contact method, the green (unroasted) beans are placed in a rotating drum and softened by steam for approximately 30 minutes; they are then repeatedly rinsed - for about 10 hours - with methylene chloride, which removes the caffeine from the beans. (This is also called the European Prep method.)

The caffeine-laden solvent is drained away and the beans are steamed a second time, for 8 - 12 hours, so the remaining solvent can evaporate. Finally, air or vacuum drying removes excess moisture from the decaffeinated beans. Virtually no solvent residue remains after roasting the beans.

In the indirect contact method, sometimes referred to as the "water process," the green beans soak for several hours in a water/caffeine solution at almost boiling temperature. Gradually the solution draws off the caffeine as well as other flavor elements and oils, from the beans.

The caffeine/water mixture is drained away and treated with methylene chloride, which absorbs the caffeine. The resulting mixture is then heated to evaporate the solvent and caffeine. Next the mixture is reunited with the beans, allowing them to regain most of the coffee oils and flavor elements. The solvent never touches the beans.

2. Swiss Water Process (Komodo Blend)
In this indirect contact method unroasted beans are circulated and soak in hot water that is saturated with coffee flavor, also known as "flavor-charged water." Activated carbon filters then removes caffeine from the "flavor-charged water" that is used again to decaffeinate the next batch of beans. The beans are then dried and bagged for sale. The coffee industry often refers to this as the Swiss Water Process because a Swiss company originally developed and patented the procedure.

3. Ethyl Acetate
Using this substance to deccaffeinate coffee is often referred to as a "natural" process because ethyl acetate is a compound found in any fruits, such as apples, peaches, and pears. This process is similar to the indirect contact method using methylene chloride described above, although ethyl acetate requires more time to absorb the caffeine.

The process begins when green coffee beans soak in a heated water/coffee solution, which gradually draws off the caffeine and flavor elements. The solution is separated from the beans and treated with ethyl acetate, a compound that absorbs caffeine.

A steaming process removes the caffeine-laden ethyl acetate from the water. The water is then returned to the beans, which reabsorb the flavor elements. Finally, the beans are dried.

Note: the USFDA has authorized by regulation the use of both methylene chloride and ethyl acetate for coffee decaffeination. According to an FDA report in the Federal Register most decaffeinated coffee has less than 0.1 parts per million (ppm) of residual methylene chloride, 100 times less than the maximum level of 10 ppm allowed by the FDA.

4. Triglycerides
Green coffee beans are soaked in a hot water/coffee solution to draw the caffeine to the surface of the beans. Next, the beans are transferred to another container and immersed in coffee oils that were obtained from spent coffee grounds.

After several hours of high temperatures, the triglycerides in the oils remove the caffeine - but not the flavor elements - form the beans. The beans are separated from the oils and dried. The caffeine is removed from the oils, which are reused to decaffeinate another batch of beans. This is a direct contact method of decaffeination.

5. Supercritical Carbon Dioxide
In the direct contact method, green beans are first softened by steam, to bring caffeine to the beans' surface. Next, they are immersed in carbon dioxide at a high temperature and pressure - in this "supercritical" state the carbon dioxide behaves as if it were a liquid while remaining a gas. It permeates the beans to extract the caffeine.

The supercritical carbon dioxide is than drawn off, leaving the beans 97% free of caffeine. The solvent residue remaining on the beans dissipates as a gas when the beans return to room temperature.

Consumer Awareness
Depending on which of the above methods is used, the loss of coffee flavor and aroma in the brewed beverage will vary. The minuscule solvent residues that may exist in the beans following decaffeination are considered safe and will not detract from the enjoyment of true gourmet coffee.

As described above, every method of decaffeination uses water. Coffees, therefore, that carry a "Water Processed" label are not necessarily decaffeinated by the "Swiss Water Process".

Also, coffee may be described as "naturally decaffeinated." This phrase is a marketing term that suggests the coffee has been decaffeinated by a natural process; no specific "natural process" exists.

back to top