Decaffeination (decaf) is the removal of caffeine from coffee beans, cocoa, tea leaves and other caffeine-containing materials. While soft drinks which do not use caffeine as an ingredient are sometimes described as "decaffeinated", they are better termed "uncaffeinated" because decaffeinated implies that there was caffeine present at one point in time. Decaffeinated drinks contain typically 1–2% of the original caffeine content, and sometimes as much as 20%.
In the case of coffee, various methods can be used. The process is usually performed on unroasted (green) beans, and starts with steaming of the beans. They are then rinsed with a solvent that extracts the caffeine while leaving other constituents largely unaffected. The process is repeated from 8 to 12 times until the caffeine content meets the required standard (97% of caffeine removed according to the international standard, or 99.9% caffeine-free by mass as per the EU standard). Coffee contains over 400 components important to the taste and aroma of the drink, so it is difficult to remove the caffeine without affecting other components.
- 1 Decaffeination processes
- 2 Decaffeinated tea
- 3 Decaffeinated coffee
- 4 Decaffito
- 5 See also
- 6 References
What all decaffeination processes have in common
In all decaffeination processes, coffee is always decaffeinated in its green, unroasted state. The greatest challenge to the decaffeination process is to try to separate only the caffeine from the coffee beans while leaving the other chemicals such as sucrose, cellulose, proteins, citric acid, tartaric acid, and formic acid at their original concentrations. This is not an easy task considering coffee contains somewhere around 1,000 chemicals that contribute to the taste and aroma. Since caffeine is a polar, water-soluble substance, water is used in all forms of decaffeination. However, water alone is not the best solution for decaffeination because it is not a selective solvent and therefore removes other soluble substances, including sugars and proteins, as well as caffeine. Therefore all decaffeination processes use a decaffeinating agent such as methylene chloride, activated charcoal, CO
2, or ethyl acetate. These agents help speed up the process and minimize the “washed-out” effects that water alone would have on the taste of decaf coffee.
The first commercially successful decaffeination process was invented by German merchant Ludwig Roselius and co-workers in 1903 and patented in 1906. Legend has it that his quest for decaffeinated coffee was motivated by the belief that excessive coffee drinking had poisoned his father. His decaffeination process involved steaming coffee beans with various acids or bases then using benzene as a solvent to remove the caffeine. Coffee decaffeinated this way was sold as Kaffee HAG after the company name Kaffee Handels-Aktien-Gesellschaft (Coffee Trading Company) in most of Europe, as Café Sanka in France and later as Sanka brand coffee in the U.S.. Café HAG and Sanka are now worldwide brands of Kraft Foods. Due to health concerns regarding benzene (which is recognised today as a proven carcinogen), this process is no longer used commercially and Coffee Hag and Sanka are produced using a different process.
Swiss Water process
The use of water as the solvent to decaffeinate coffee was originally pioneered in Switzerland in 1933 and developed as a commercially viable method of decaffeination by Coffex S.A. in 1980. In 1988 the Swiss Water Method was finally introduced to the market and its facility is based near Vancouver, British Columbia, Canada.This method is now used commercially under the trade-mark "Swiss Water Process" by The Swiss Water Decaffeinated Coffee Company of Burnaby, British Columbia, Canada. The Swiss Water Company’s decaffeination facility is the only facility in the world certified organic by both OCIA and Aurora Certified Organic. Additionally, they are also certified Kosher by the Kosher Overseers Association.
This method is different in that it does not directly or indirectly add chemicals to extract the caffeine. Rather, it relies entirely on two concepts - solubility and osmosis - to decaffeinate coffee beans. The process begins by immersing a batch of green coffee beans in very hot water in order to dissolve and extract the caffeine. The water is then drawn off and passed through an activated charcoal filter. The porosity of this filter is sized to only capture larger caffeine molecules, while allowing smaller oil and flavor molecules to pass through it. However, this extraction process will also extract desirable oils and other solids from the beans, resulting in beans with no caffeine and no flavor in one tank, and caffeine-free but with flavor water in another tank. The Swiss Water process method attempts to overcome this difficulty by first discarding the flavorless caffeine-free beans, and then reusing the flavor rich water to remove the caffeine from a fresh batch of coffee beans. Water saturated in this way is referred to as green coffee extract or GCE. It is created using a separate batch of green coffee beans, which are immersed in water and then discarded. In a pre-loading tank water, cane sugar and formic acid are mixed and heated and used to preload carbon filter columns. The GCE is then filtered over the columns to extract caffeine from it. A fresh batch of green coffee beans is then immersed in the GCE to remove caffeine but retain other components. The other components can be retained because the water is already saturated with flavor ingredients, therefore, the flavors in this fresh bath cannot dissolve - only caffeine moves from the coffee beans to the water. This results in decaffeination without a massive loss of flavor. The process of filtering the GCE to remove caffeine and immersing the beans is repeated until the beans are 99.9% caffeine free by mass, meeting the required standard. This process takes 8 to 10 hours. US US5208056, Kummer, Peter & Arthur Fischer, "Process for decaffeinating raw coffee", issued May 4, 1993
Solvents used in decaffeination
Given numerous health scares connected to early efforts in decaffeination using toxic solvents includes such as benzene, trichloroethylene, dichloromethane and even chloroform, the solvents of choice have become dichloromethane and ethyl acetate. Dichloromethane is able to extract the caffeine selectively and has a low boiling point. Although it is a solvent, its use as a decaffeination agent is not considered a health risk. In fact the Food and Drug Administration has determined any potential health risk is so low “as to be essentially non-existent”. While the FDA regulation allows up to ten parts per million (ppm) residual dichloromethane, actual coffee industry practice result in levels closer to one part per million. Although it is probable that traces of the solvent remain in the decaffeinated beans, it seems very unlikely that dichloromethane would survive the roasting process. Dichloromethane is highly volatile and vaporizes at 104F and coffee is roasted at a minimum of 400F for at least 15 minutes. Ethyl acetate is known to be more natural than other chemicals and safer than dichloromethane because it exists in several natural products and contributes to the characteristic aroma of many fruit. Ethyl acetate is also found in varying concentrations in foodstuffs including green and roasted coffee. Because ethyl acetate occurs in nature, coffee beans decaffeinated with this method are often labeled as “naturally” decaffeinated.
In the direct method, the coffee beans are first steamed for 30 minutes to open their pores and then repeatedly rinsed with either dichloromethane or ethyl acetate for about 10 hours to remove the caffeine. The caffeine-laden solvent is then drained away and the beans steamed for an additional 10 hours to remove residual solvent. Sometimes coffees that are decaffeinated using ethyl acetate are referred to as naturally processed because ethyl acetate can be derived from various fruits or vegetables, but because of the impracticality of gathering natural ethyl acetate, the ethyl acetate used for decaffeination is synthetic.
In the indirect method, beans are first soaked in hot water for several hours, in essence making a strong pot of coffee. Then the beans are removed and either dichloromethane 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, wherein 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, indirect method decaffeination is sometimes referred to as "water-processed".
This process has been referred to as CO2 Method, Liquid Carbon Dioxide Method, and Supercritical Carbon Dioxide method but it is technically known as supercritical fluid extraction. This method is the most recent method developed by Kurt Zosel, a scientist of the Max Plank Institute, and uses liquid CO2 in place of chemical solvents.
The supercritical CO2 acts selectively on the caffeine, releasing the alkaloid and nothing else. Water soaked coffee beans are placed in an extraction vessel. The extractor is then sealed and liquid CO2 is forced into the coffee at pressures of 1,000 pounds per square inch to extract the caffeine. The CO2 acts as the solvent to dissolve and draw the caffeine from the coffee beans, leaving the larger-molecule flavor components behind. The caffeine laden CO2 is then transferred to another container called the absorption chamber where the pressure is released and the CO2 returns to its gaseous state and evaporates, leaving the caffeine behind. The caffeine is removed from the CO2 using charcoal filters and the caffeine free CO2 is pumped back into a pressurized container for reuse on another batch of beans. This process has the advantage that it avoids the use of potentially harmful substances. Because of its cost, this process is primarily used to decaffeinate large quantities of commercial-grade, less-exotic coffee found in grocery stores.
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.
Tea may also be decaffeinated, usually by using processes analogous to the direct method or the CO2 process, as described above. The process of oxidizing tea leaves to create black tea ("red" in Chinese tea culture) or oolong tea leaves from green leaves, does not affect the amount of caffeine 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.
Certain processes during normal production might help to decrease the caffeine content directly, or simply lower the rate at which it is released throughout each infusion. Several instances in China where this is evident is in many cooked pu-erh teas, as well as more heavily fired Wuyi Mountain oolongs; commonly referred to as 'zhonghuo' (mid-fired) or 'zuhuo' (high-fired).
A generally accepted statistic is that a cup of normal black (often called red in China; as distinct from green) tea contains 40–50 mg of caffeine, roughly half the content of a cup of coffee.
Although a common technique of discarding a short (30- to 60-second) steep is believed to much reduce caffeine content of a subsequent brew at the cost of some loss of flavor, 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).
Caffeine content of decaffeinated coffee
A controlled study of ten samples of prepared decaffeinated coffee from coffee shops showed that some caffeine remained. Fourteen to twenty cups of such decaffeinated coffee would contain as much caffeine as one cup of regular coffee. The 16-ounce (473-ml) cups of coffee samples contained caffeine in the range of 8.6 mg to 13.9 mg. In another study of popular brands of decaf coffees, the caffeine content varied from 3 mg to 32 mg. An 8-ounce (237-ml) cup of regular coffee contains 95–200 mg of caffeine, and a 12-ounce (355-milliliter) serving of Coca-Cola contains 36 mg.
Both of these studies tested the caffeine content of store-brewed coffee, suggesting that the caffeine may be residual from the normal coffee served rather than poorly decaffeinated coffee.
As of 2009, progress toward growing coffee beans that do not contain caffeine was still continuing. The term "Decaffito" has been coined to describe this type of decaffeinated coffee, and trademarked in Brazil.
The prospect for Decaffito-type coffees was shown by the discovery of the naturally caffeine-free Coffea charrieriana, reported in 2004. It has a deficient caffeine synthase gene, leading it to accumulate theobromine instead of converting it to caffeine. Either this trait could be bred into other coffee plants by crossing them with C. charrieriana, or an equivalent effect could be achieved by knocking out the gene for caffeine synthase in normal coffee plants.
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