Decaffeination

Decaffeination is the act of removing caffeine from coffee beans, mate, cocoa, tea leaves and other caffeine containing materials. (While caffeine-free soft drinks are occasionally referred to as "decaffeinated," some are actually prepared by simply omitting caffeine from production.)

In the case of coffee, the decaffeination processes are performed on unroasted (green) beans, but the methods vary somewhat. It generally starts with the steaming of the beans. They are then rinsed in solvent that contains as much of the chemical composition of coffee as possible without also containing the caffeine in a soluble form. The process is repeated anywhere from 8 to 12 times until it meets either the international standard of having removed 97% of the caffeine in the beans or the EU standard of having the beans 99.9% caffeine free by mass. Coffee contains over 400 chemicals important to the taste and aroma of the final drink; this effectively means that no physical process or chemical reaction will remove only caffeine while leaving the other chemicals at their original concentrations.

Coffea arabica normally contains about half the caffeine of Coffea robusta. A Coffea arabica bean containing little caffeine has been found recently in Ethiopia.^[1] This may change how low-caffeine coffee is produced in the future. Additionally, genetic engineering technology may be eventually applied to create a "naturally" caffeine-free coffee. But for now, one of several methods to remove the caffeine from caffeine-containing beans is employed.

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Roselius process

The first commercially successful decaffeination process was invented by Ludwig Roselius and Karl Wimmer in 1903. It involved steaming coffee beans with a brine (salt water) solution and then using benzene as a solvent to remove the caffeine. Coffee decaffeinated this way was sold as Coffee (Kaffee, Koffie etc) HAG (from Kaffee Handels Gesellschaft or Coffee Trading Company) in most of Europe , as Café Sanka in France and later as Sanka brand coffee in the US. Due to health concerns regarding benzene, this process is no longer used commercially and Coffee Hag and Sanka are produced using a different process.

Swiss water process

The Swiss Water Process is a method of decaffeinating coffee beans that was developed by the Swiss Water Decaffeinated Coffee Company. To decaffeinate the coffee bean by the Swiss Water method, a batch of green (unroasted) beans is soaked in hot water, releasing caffeine. This process is done until all the caffeine and coffee solids are released into the water. These beans are then discarded. Next, the water passes through a carbon filter which traps the caffeine molecules but allows the water and the coffee solids to pass through. The caffeine-free water which comes through, known as "flavor-charged" water by the company, is then put in a similar filtration device, and new coffee beans are added. However, since the flavor-charged water cannot remove any of the coffee solids from the new beans, only the caffeine is released. The process repeats, filtering out all the caffeine until the beans are 99.9% caffeine free. These beans are removed and dried, and thus retain most if not all of their flavour and smell.

Although the process originated in Switzerland in the 1930s, today the world's only Swiss Water decaffeination facility is based near Vancouver, Canada^[2].

Direct method

In the direct method the coffee beans are first steamed for 30 minutes and then repeatedly rinsed with either methylene chloride or ethyl acetate for about 10 hours. The solvent is then drained away and the beans steamed for an additional 10 hours to remove any residual solvent. Sometimes coffees which are decaffeinated using ethyl acetate are referred to as naturally processed because ethyl acetate can be derived from various fruits or vegetables. However, for the purpose of decaffeination, it is not generally possible to create such a large quantity of ethyl acetate, thus the chemical is synthetically derived.

Indirect method

In the indirect method beans are first soaked in hot water for several hours, essentially making a strong pot of coffee. Then the beans are removed and either methylene chloride or ethyl acetate is used to extract the caffeine from the water—as in other methods, the caffeine can then be separated from the organic solvent by simple evaporation. The same water is recycled through this two-step process with new batches of beans. An equilibrium is reached after several cycles, where the water and the beans have a similar composition except for the caffeine. After this point, the caffeine is the only material removed from the beans, so no coffee strength or other flavorings are lost. Because water is used in the initial phase of this process, sometimes indirect method decaffeination is referred to as "water processed" even though chemicals are used.

CO₂/O₂ process

This process is technically known as supercritical fluid extraction. With the CO₂ process, pre-steamed beans are soaked in a liquid bath of carbon dioxide at 73 to 300 atmospheres. After a thorough soaking, the pressure is reduced allowing the CO₂ to evaporate, or the pressurized CO₂ is run through either water or charcoal filters to remove the caffeine. The carbon dioxide is then used on another batch of beans.^[3] This same process can also be done with oxygen (O₂). These liquids work better than water because they are kept in supercritical state near the transition from liquid to gas so that they have the high diffusion of gas and the high density of a liquid. This process has the advantage that it avoids the use of potentially toxic solvents.

Triglyceride process

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 - from 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.

Decaffeinated tea

Tea may also be decaffeinated, usually by using processes analogous to the Direct Method or the CO₂ process as described above. Fermentation (i.e. the process of oxidizing tea leaves to create "black," "red," or "oolong" tea leaves from green leaves) does not affect the amount of caffeine present in the tea, though tea plant species (i.e. Camellia sinensis sinensis vs. Camellia sinensis assamica) may differ in natural caffeine content. Younger leaves and buds contain more caffeine per weight than older leaves and stems. A generally accepted statistic is that a cup of tea contains 40-50 mg of caffeine, roughly half the content of a cup of coffee. ^[4] Although a common technique of discarding a short (30-60 second) steep is believed to reduce caffeine content in a subsequent brew by 80-90%, research suggests that a five minute steep yields up to 70% of the caffeine, and a second steep has one third the caffeine of the first (about 23% of the total caffeine in the leaves).^[5]

Caffeine content of decaffeinated coffee

Almost all brands of decaffeinated coffee still contain some caffeine.^[6] Drinking ten cups of decaffeinated coffee could deliver as much caffeine as one or two cups of regular coffee, according to research at the University of Florida Maples Center for Forensic Medicine.^{[citation needed]} However, in June 2004, a naturally caffeine-free bean has been produced.^[7]

References

1. ^ "Scientists discover decaf coffee bean", Guardian Unlimited, June 24, 2004. 
2. ^ History of the SWISS WATER® Decaffeination Process , Jan 04, 2007
3. ^ Coffee Decaffeination. Retrieved on 2007-12-17.
4. ^ Upton Tea Imports (2003). "Tea and Caffeine". Upton Tea Imports Newsletter 16 (1). Retrieved on 2007-01-26.
5. ^ Monique B. Hicks, Y-H. Peggy Hsieh and Leonard N. Bell (1996). "Tea preparation and its influence on methylxanthine concentration (abstract)". Food Research International 29 (3-4). Retrieved on 2007-08-22.
6. ^ "Study: Decaf coffee is not caffeine-free" UPI, October 10, 2006, at ScienceDaily.com. viewed 28/06/2007
7. ^ "Naturally decaffeinated coffee plant discovered", NewScientist.com, June 23, 2004

• Ramalakshmi K., Raghavan B. (1999). "Caffeine in coffee: Its removal. Why and how?". Critical Rev. Food Sci. Nutrition 39: 441-456. doi:10.1080/10408699991279231.