Caffeine aside, if you choose to drink decaf you must really love coffee. Coffee brands offering specialty coffees should consider, if they are not already, crafting decaf for the true coffee-lovers as, chances are, they will become their most loyal customers.

A cup that contains 6 ounces of coffee can have up to 50-75 mg of caffeine and so decaf should have less than 10 mg. Although preparation methods and bean types can potentially affect the caffeine amount in each cup, separate special methods are required to make beans lose their caffeine content, enough to make it palatable for those sensitive to caffeine.

Enough in a sense because decaffeinated coffee is not 100 percent caffeine free. According to the USDA standards, a 12 ounce cup of decaf may have 5.4 mg of caffeine instead of 180 mg that it originally might have had. So it needs to be 97% caffeine free.

In the beginning the process that was discovered effectively removing caffeine, involved benzene. The method is considered toxic these days and is abandoned. It was discovered by Ludwig Roselius in 1905.

There are four decaffeination methods popularly in use. Before we discuss what is different in each method, it might be interesting to know what remains same in either of the processes. Caffeine is always extracted from the green (un-roasted) beans regardless of the decaf process applied. Water is used as the solvent in two out of three methods and the green beans are always presoaked in water (or steam) before they get treated.
Water is not selective when it comes to dissolving or removing substances from coffee beans and hence creates a washed out feeling in the decaf coffee ripping it off of not just caffeine but many the other chemicals that give coffee its characteristic taste and aroma. Further assistance is obtained using decaffeinating agents. Methylene chloride, ethyl acetate, activated charcoal and or highly compressed CO2 are popularly used.

Ethyl acetate is a naturally found ester in fruits and vegetables. When ethyl acetate obtained from natural source is used as solvent in the decaf process the coffee is said to be naturally decaffeinated. Other solvent used in the similar manner is methylene chloride and both solvent based methods can be divided into direct and indirect categories.

1- In the direct solvent processing, as the name states the solvent comes in direct contact with the beans. For the direct solvent based processing the beans are soaked in steam rather than hot water. Once swelled up the beans are introduced directly to either of the solvents (ethyl acetate or methyl chloride) repeatedly. After being removed from the solvent the beans are steamed again to get rid of any solvent retained within the beans. The method usually uses ethyl acetate as the solvent and is the one referred to when beans are labeled “naturally decaffeinated”.

2- In the indirect solvent processing, beans are first soaked in water to draw out caffeine content and then that water is treated with the solvent, in separate container. For the indirect solvent based method beans are presoaked in hot water for many hours. That way caffeine and other oils from the beans get dissolved in hot water. The beans are then removed from the water, which is the mixed with solvent. Water and solvent mixture is then heated so that the solvent molecules (that have already selectively reacted with caffeine) may evaporate. The liquid is then returned to the beans to reabsorb the oils and flavors as much as possible. This method is particularly popular in Europe with methylene chloride used as solvent.

For people feeling concerned about residual solvent in the beans; both the solvents are volatile in nature and is highly unlikely that solvent molecules may escape the high temperature of steaming or roasting that follows.

3- Another method uses activated charcoal to remove caffeine from the coffee beans and is also called Swiss Water Process (SWP) because it began back in 1933 in Switzerland. The process is highly effective when it comes to retaining the flavor. Beans are first soaked in hot water to get the caffeine out. The water is then moved to another tank passing through an activated charcoal filter. The pore size of the filter is set to stop the larger caffeine molecules while allowing the passage of smaller oil molecules and other flavors.
As a result the final tank contains water that has all the flavors and oils but no caffeine. The batch of beans used for the first attempt is discarded. The water is retained and reused. As it is now saturated with flavors and oils the next batch of coffee beans is soaked in the same water. This time only caffeine is lost by the beans and no flavor oils because the water in the outer environment is already saturated with them courtesy of the first batch. Caffeine is absorbed by the activated carbon filters and beans move through while not losing much of their flavor. The method is labeled as “Swiss Water Decaf”.

4- Finally the CO2 method. Since it is expensive, only huge batches of commercial grade coffee is treated via this method to remove caffeine. Discovered by Kurt Zosel, the method reacts with only caffeine and nothing else. In a stainless steel container presoaked beans (water soaked) are mixed with liquid CO2 after the container is sealed tight and the gas is basically forced at 1000 pounds per square inch into the container. Now formed as solvent, CO2 reacts with caffeine in the beans and not with the other oils and flavors. The gas is then released into the next tank with pressure lifted CO2 returns back to gaseous state and caffeine separates from the gas. Cleared up gas is then reused in the same manner.

It is almost impossible to get exact tasting decaf as non-decaf coffee because pre-soaking and then getting the beans dried up back again before roasting make them difficult to roast actually. Decaffeinated coffee makes up about 12 percent of coffee industry so there are many options in the market for these real coffee loves. If you are one of them, do some tasting and decide for yourself which decaf process gives off the best decaf experience.

Sources:
http://www.coffeeconfidential.org/health/decaffeination/
http://coffeeandhealth.org/all-about-coffee/decaffeination/
https://www.scientificamerican.com/article/how-is-caffeine-removed-t/
http://www.todayifoundout.com/index.php/2011/04/how-decaffeinated-coffee-is-made/