Views: 0 Author: Site Editor Publish Time: 2020-05-22 Origin: Site
CO2 / Carbon Dioxide - CO2 decaffeination uses highly compressed carbon dioxide gas, which becomes a fluid under pressure. CO2 is totally safe and is effective at removing caffeine. The CO2 process is good at preserving flavor; its main downside is that it is expensive.
Ethyl Acetate - Ethyl acetate is a naturally occurring compound, common in fruit (and also occurring in small concentration in tea leaf). It is completely safe at the levels in which it remains in the tea after decaffeination. The ethyl acetate process is inexpensive, but it has the disadvantage of removing more flavor than other methods.
Methylene Chloride / Dichloromethane - Methylene chloride, also called dichloromethane, is effective at extracting caffeine while leaving other flavors intact. However, it is a probable carcinogen and is toxic in large concentrations. Its use in decaffeination is legal in the U.S. but regulated by the FDA. Methylene chloride probably does not pose a large health risk in the low concentrations left in most decaf tea, but teas analyzed in the past have been found to have levels exceeding the legal limit. Companies using this process generally do not announce it due to the negative public perception of this chemical.
Benzene - The original decaffeination processes used benzene as a solvent. Benzene is a dangerous chemical and can cause cancer and numerous other health problems. It is not safe for use in decaffeination, and fortunately, its use for this process has been banned and discontinued long ago.
Trichloroethylene - Another organic solvent that has been banned and discontinued for use in decaffeination, trichloroethylene was abandoned after it was found to cause liver tumors in mice.
How Coffee is Decaffeinated
First, let's start with a really quick history. Coffee was first decaffeinated by Ludwig Roselius, a German coffee merchant, in 1905 after he received a coffee shipment that had gotten soaked during a storm at sea. He experimented with the brine-soaked coffee and found out that benzene could be used as solvent to bond with the caffeine. Since caffeine is water-soluble at temperatures above 175°, he could boil the solution to separate the caffeine from the coffee. With his process, the coffee was decaffeinated, but it had lost much of its flavor.
For the record, Ludwig improved on his process and went on to sell his discovery under the Sanka brand name. Benzene is no longer used, as it is not considered safe for human consumption.
Today there are 3 commonly used methods available for removing caffeine from coffee, with dozens of variations of those methods. Two common variations are Direct and Indirect Method.
European or Traditional Process - Direct Method:
The direct process involves softening the beans by steam first, then washing them for about 10 hours with either a methylene chloride or ethyl acetate solution to absorb the caffeine from the bean. The solution is discarded, the beans are re-steamed to remove any remaining solvent (methylene chloride boils away at 114°; ethyl acetate at 104°), then the beans are dried to their original moisture content.
European or Traditional Process - Indirect Method:
Instead of being steamed, the coffee beans are soaked in very hot water, which extracts the caffeine along with many of the oils. This solution is then treated with either methylene chloride or ethyl acetate, which bonds with the caffeine. Then the solution is heated to the temperature at which the caffeine and either methylene chloride or ethyl acetate compounds evaporate. The oils are then reintroduced to the beans, and the beans are then dried.
About 80% of decaf coffees are processed by the Traditional, or European Process, and many serious coffee drinkers believe this method makes for the best-tasting coffee. Others worry about the chemicals involved. Methylene chloride is considered a superior solvent since it can evaporate at a lower temperature and leaves virtually no trace in the beans, but it is an environmental hazard to workers at decaffeination plants, and it is known to harm the ozone layer. Ethyl acetate can be extracted from various fruits and vegetables and so it is considered a "naturally-found" chemical, but most ethyl acetate used for decaffeinating is synthetically produced.
The Water or Swiss Water Process:
Also known as the water process, this process uses no chemicals, but rather hot water, steam and osmosis to remove the caffeine from the coffee in two steps. In the first step, which is similar to the Traditional, Indirect Method, the beans are soaked in a hot water solution to remove the caffeine and the flavor oils. The beans used in this step are then discarded. The solution is run through activated charcoal filters to remove the caffeine but leave the flavor oils. A new batch of beans is then soaked in the solution. According to the laws of osmosis, the caffeine leaves the beans to go to the caffeinated solution, but the flavor in both the solution and the beans is equal, so no flavor leaves the beans.
The beans are then dried and shipped to the roasters. The disadvantage is that the water processing removes more than just the caffeine. Some of the oils from the coffee bean are removed as well, making it less flavorful.
The Hypercritical Carbon Dioxide Method:
In this method, which is not as popular as the other methods, the beans are soaked in a solution of liquid carbon dioxide to remove the caffeine. The get to a liquid state, the carbon dioxide must be highly pressurized (73 to 300 atmospheres), which makes the logistic cost of this method a bit higher than the other methods. After the caffeine is absorbed by the carbon dioxide, either the pressure is reduced and carbon dioxide is allowed to evaporate, or the solution is run through a carbon filter to remove the caffeine. Although more expensive, the advantage of the Carbon Dioxide Method is that since carbon dioxide is not a harmful gas, the method is not harmful to health or the environment.