Caffeine occurs naturally in more than 60 plants, including:
- the arabica plant, which produces coffee beans
- the Theobroma cacao tree, which produces the beans that are the primary ingredient in chocolate
- kola nuts, which many cola drink products are made with
- the Thea sinensis plant, whose leaves are used for teas
When separated from its sources, caffeine is a white, bitter-tasting powder. See How Caffeine Works for more information about caffeine.
Several methods are used to remove caffeine from its natural sources:
- Methylene chloride processing
- Ethyl acetate processing
- Carbon dioxide processing
- Water processing
Methylene chloride is a chemical used as a solvent to extract caffeine from many raw materials. Molecules of caffeine bond to molecules of methylene chloride. The materials are softened in a water bath or in steam. The next step is to process the materials with methylene chloride by either of two methods:
- Using the "direct" method, caffeine is removed by directly soaking the materials in methylene chloride.
- Using the "indirect" method, caffeine, which is water soluble, is extracted by soaking the materials in water. Many of the flavors and oils are also extracted during this process, so the solution is treated with methylene chloride and then returned to the material for reabsorption of the flavorings.
Ethyl acetate processed products are referred to as "naturally decaffeinated" because ethyl acetate is a chemical found naturally in many fruits. Caffeine is extracted in the same way as with methylene chloride processing, but ethyl acetate is the solvent.
To decaffeinate using carbon dioxide (CO2), water-softened materials are "pressure cooked" with the gas. At high pressures and high temperatures, carbon dioxide is in a supercritical state, acting as both a gas and a liquid. It becomes a solvent with its small, nonpolar molecules attracting the small caffeine molecules. Since flavor molecules are larger, they remain intact, which is why this process retains the flavor of the material better.
Caffeine extraction with water is used primarily for coffee decaffeination. The process is similar to the "indirect" method used in methylene chloride processing, but no chemicals are used. After the caffeine is leached out of the material by soaking in hot water for a period of time, the solution is then passed through a carbon filter for caffeine removal. The water is then returned to the beans for reabsorption of flavors and oils. In the "Swiss Water Process," the same method is used, but instead of soaking in water, the beans are soaked in a coffee-flavored solution. This results in the caffeine being extracted without removing the coffee flavors.
Caffeine is not removed completely using any of these methods, but under federal regulations in the United States, caffeine levels must not be above 2.5 percent of the product in order for a product to be labeled "decaffeinated."
Most of the caffeine removed in processing is manufactured for use in other products, such as medicines and soft drinks. For example, less than 5 percent of the caffeine found in cola drinks is actually from the kola nut, and many of the popular "high caffeine" soft drinks do not contain kola nut extracts at all. The caffeine content of soft drinks is primarily, and sometimes completely, from the addition of caffeine extracted from decaffeination processes.