So, the coffee bean comes with a certain amount of caffeine in it, but the caffeine can be removed while leaving the coffee bean intact.
How does decaf work?
The answer is that it is a lengthy process that often uses chemicals.
The hard thing about removing caffeine is that, in addition to the caffeine, coffee contains about 1000 other chemical compounds – many of which contribute to the flavor profile. Therefore, the challenge is to remove the caffeine without removing the flavor. To do that requires a solvent that can enter the bean and dissolve the caffeine and remove it while leaving everything else – this is where the chemicals come into play.
The Inventor of Decaf Coffee
German coffee merchant Ludwig Roselius patented the first method for coffee decaffeination in 1906. Since caffeine is water-soluble at temperatures above 175°, his process involved boiling the beans in a saltwater solution to separate the caffeine from the coffee, and then using benzene as a solvent to extract the caffeine. His process removed much of the caffeine, but it also removed lots of flavor from the coffee. It was also later discovered that benzene is a carcinogenic, which made his method less than desirable
For the record, Roselius improved on his process and went on to sell his discovery under the Sanka brand name.
How Decaf is Done Today
There are currently 5 common methods used for removing caffeine from coffee:
• Traditional Process – Direct Method:
All of the processes decaffeinate the bean while it is still in green, unroasted form. The direct method process involves steaming the green coffee beans for about 30 minutes to soften them and open their pores, then washing them for about 10 hours in a solution of either a methylene chloride or ethyl acetate to absorb the caffeine from the bean.
The solution containing the caffeine is then discarded, and the beans are re-steamed to remove any remaining solvent (methylene chloride boils away at 104°; ethyl acetate at 114°). After that, the beans are dried back to their original moisture content.
In the direct method, ethyl acetate is used as the solvent more often than methylene chloride. Since ethyl acetate can be extracted from various fruits and vegetables, it is considered a “naturally-found” chemical, and this method is often referred to as the “The Natural Decaffeination Method.” In truth, however, most ethyl acetate used for decaffeinating is synthethically produced.
• European Process – Indirect Method:
In this method, the coffee beans are soaked in very hot water instead of being steamed. The caffeine is extracted from the bean along with many of the oils and flavor compounds. The extracted solution is then treated for 10 hours with either methylene chloride or ethyl acetate, which bonds with the caffeine.
The solution is then heated to the temperature at which the solution with the caffeine and either methylene chloride or ethyl acetate evaporates. The remaining solution with the oils and flavor compounds is then reintroduced to the beans, and then the beans are dried.
About 80% of decaf coffees are processed by this method. It is very popular in Europe and especially in Germany, and many coffee drinkers believe this method makes for the best-tasting decaf coffee.
There are concerns about the chemicals, however. Methylene chloride is usually used as the solvent because it can evaporate at a lower temperature and leaves virtually no trace in the beans. It evaporates at 104°, and the coffee is roasted at 400°, so, it is all burned out of the finished product. However, it is an environmental hazard to workers at decaffeination plants, and it is known to harm the ozone layer.
• The 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 European, 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 then run through activated charcoal filters to remove the caffeine but leave the flavor and oils.
The caffeine solution that results is known as Green Coffee Extract.
For the second step, a new batch of beans is added to this solution for soaking, and, according to the laws of osmosis, the caffeine leaves the beans to go to the decaffeinated solution, but since the flavor and oils in both the solution and the beans is equal, minimal flavor and oils leaves the beans. The beans are then dried back to their original moisture content.
This is a very good method, but, similar to Roselius’ first method, some of the flavors and oils are get removed with the caffeine, resulting in coffee with some flavor loss.
• The Hypercritical Carbon Dioxide Method:
This newer method is also known as the CO2 Method or the Liquid Carbon Dioxide Method. It is not as popular as the other methods, partly because it is more expensive.
In this method, the caffeine is removed by soaking the beans in a solution of liquid carbon dioxide. To get the carbon dioxide to a liquid state, it must be highly pressurized to a state of 73 to 300 atmospheres. After the caffeine is absorbed by the carbon dioxide, the pressure is reduced and carbon dioxide evaporate and carries the caffeine with it.
The cost of the high pressurization is high, but 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.
• Triglyceride Method
In this method, the green coffee beans are soaked in a solution of hot water and coffee to open the pores of the bean. The beans are then transferred to another container and immersed in a solution containing coffee oils that were obtained from spent coffee grounds. The solution is heated to a high temperature for several hours, and the triglycerides in the oils remove the caffeine from the beans while leaving the oils and flavors.
The beans are then dried while the caffeine is removed from the oils so that they can be used to decaffeinate another batch.
No Perfect Method For Making Decaf
The jury is still out on which method is the best, and there will be new methods developed. The problem with all of the above methods is that they don’t always remove all of the caffeine, and that they all remove some of the flavor from the coffee.
According to the USDA, coffee must be 97% caffeine-free in order to be declared decaf. Therefore, decaf coffee generally does still contain some caffeine. A regular 12 oz. cup of coffee would usually contain about 180 mg of caffeine, but a decaf coffee might still contain 5.4 mg of caffeine.
There is hope, however: the future of decaffeinated coffee may be the cultivation of Naturally Caffeine-Free Coffee from trees that have been discovered that produce beans containing no caffeine.
Regardless, the next time you order decaf coffee, maybe you can appreciate the work that went into making that cup.