Water Process Decaffeinated Coffee

All coffee can be decaffeinated. The challenge is that once picked, washed and dried at the coffee farm, rarely is the coffee also decaffeinated there too. Coffee is sent to decaffeination processing plants all over the world. Coffee grown and processed in South America, for example, will be sent to Canada to be decaffeinated. This is an expensive and time consuming extra step to get the final decaffeinated dried beans to the roaster. Hence why decaffeinated beans are often more expensive because of the multi-step process of removing the caffeine. Some standards worldwide require that the process of decaffeination eliminate 99.9% of the alkaloid from the coffee. The FDA requires at least 97% decaffeination in the US.

The Decaffeination Basics

Caffeine is water soluble. That's why the water goes into the grounds clear and clean and comes out brown and buzzing: the caffeine dissolves at an extraction rate that's determined by the size of your grinds and the temperature of the water.

In order to decaffeinate coffee, the soluble caffeine needs to be taken out of the bean, while leaving as much of the delicious flavor intact. This can be done in several ways, but the best and most natural option is a water process decaffeination. The greatest challenge is to try to separate only the caffeine from the coffee beans while leaving the other compounds at their original concentrations. This is not easy since coffee contains somewhere around 1,000 different compounds that are important to the taste and aroma of this wonderfully complex elixir.

Since caffeine is a water-soluble substance, water is used in all forms of decaffeination. However, water by itself is not the most efficient solution for decaffeination. Water is not a “selective” solvent and therefore removes other soluble substances, like sugars and proteins, as well as caffeine. Therefore, all decaffeination processes use a decaffeinating agent (such as methylene chloride, activated charcoal, CO2, 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 Decaffeination Details

The Water Process, aka The Swiss Water Process, Decaffeination Process (the method our decaf is decaffeinated with)

This water decaffeination process was pioneered in Switzerland in 1933 and developed as a commercially viable method in 1980. In 1988 the Swiss Water Method was finally introduced to the market and its facility is based near Vancouver, British Columbia, Canada. The Swiss Water Company’s decaffeination facility is the only facility in the world certified organic and Kosher.

This particular method of decaffeination is different in that it does not directly or indirectly add chemicals to extract the caffeine. Rather, it relies on solubility and osmosis. It begins by soaking a batch of beans in very hot water in order to dissolve 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. Consequently we end up with beans with no caffeine and no flavor in one tank, and caffeine-free “flavor charged” water (aka “Green Coffee Extract”) in another tank. The flavorless caffeine-free beans are discarded, but the flavor-rich water is reused to remove the caffeine from a fresh batch of coffee beans. Since this water already is saturated with flavor ingredients the flavors in this fresh batch can’t dissolve; only caffeine moves from the coffee beans to the water. So the result is decaffeination without a massive loss of flavor. This method is exclusively used for decaffeination of organic coffee. Coffee decaffeinated using this environment-friendly Swiss Water Process undergoes regular caffeine level audits to ensure compliance to 99.9% caffeine-free.

The Chemical aka "Solvent" Decaffeination Process

The Roselius Process: The first commercially successful decaffeination process was invented by the German coffee merchant Ludwig Roselius 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 process involved steaming coffee beans with a brine solution (i.e., water, saturated with salt) and then using the organic chemical compound benzene as a solvent to extract the caffeine. This process, however, is no longer used due to the fact that benzene is known to be a human carcinogen.

Solvent based processes are those in which the caffeine is removed from the beans with the help of a chemical solvent, such as methylene chloride or ethyl acetate. They can be divided into methods using the “direct” method versus the “indirect” method. In the direct method, caffeine is removed by soaking the materials directly in a solvent. In the indirect method the caffeine-laden water is transferred to a separate tank and treated with a solvent; in this case the solvent never touches the beans. Given numerous health scares connected to early efforts in decaffeination science (the list of toxic solvents includes: benzene, trichloroethylene (TCE), dichloromethane and even chloroform) the solvents of choice have become methylene chloride and ethyl acetate. Although methylene chloride is a solvent, its use as a decaffeination agent is not considered a health risk. In fact the FDA has determined any potential health risk is so low “as to be essentially non-existent”. While it is probable that traces of the solvent remain in the decaffeinated beans it seems very unlikely that methylene chloride would survive the roasting process. This colorless liquid is highly volatile and vaporizes at 104
ºF. Now if you take into consideration that coffee is roasted at a minimum of 400ºF for at least 15 minutes, and that proper brewing temperature is at about 200ºF, it seems unlikely that much methylene chloride would end up in your cup. Ethyl acetate is considered more natural than other chemicals and is akin to vinegar, and safer than methylene chloride since it exists in minute quantities in ripening fruits, such as apples and blackberries. However, because of the impracticality of gathering natural ethyl acetate and its cost, often the compound used in decaffeination is synthetic. Ethyl acetate is produced commercially from ethyl alcohol and acetic acid, which in turn may be produced from natural ingredients or petroleum derivatives. Two years ago we had a sugar cane derived ethyl acetate decaf Colombia that was quite fruity, unique and delicious.

1) The Indirect–Chemical Process: In the indirect-chemical method the coffee beans are soaked in near boiling water for several hours, which extracts the caffeine as well as other flavor elements and oils from the beans. The water is then separated and transferred to another tank where the beans are washed for about 10 hours with either methylene chloride or ethyl acetate. The molecules of the chemical solvent selectively bond with the molecules of caffeine and the resulting mixture is then heated to evaporate the solvent and caffeine. Lastly, the beans are reintroduced to the liquid to reabsorb most of the coffee oils and flavor elements. This method is very popular in Europe, especially in Germany, and primarily uses methylene chloride as solvent.

2) The Direct–Chemical Based Process: The beans are steamed for about 30 minutes in order to open their pores. Once the coffee beans are receptive to a solvent, they are repeatedly rinsed with either methylene chloride or ethyl acetate for about 10 hours to remove the caffeine. The caffeine-laden solvent is then drained away and the beans are steamed again to remove any residual solvent. Most of the time the solvent of choice in this method is ethyl acetate.
3) The Carbon Dioxide (CO2) MethodIs a newer method developed by Kurt Zosel, a scientist of the Max Plank Institute, and uses liquid CO2 in place of chemical solvents. It acts selectively on the caffeine, i.e., it releases the alkaloid and nothing else. In this process, water-soaked coffee beans are placed in a stainless steel container called the 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. Here the pressure is released and the CO2 returns to its gaseous state, leaving the caffeine behind. The caffeine free CO2 gas is pumped back into a pressurized container for reuse. Because of its cost, this process is primarily used to decaffeinate large quantities of commercial-grade, less-exotic coffee.

Why is it so Difficult to Make Good Decaf Coffee?

Decaf coffee drinkers know that finding a good decaf coffee is the exception rather than the norm. The reason for this centers around two problems that are very difficult to overcome. First, the decaffeination process tends to damage many flavor compounds that contribute to the sensory character of roasted coffee. Secondly, decaf coffees are notoriously difficult to roast. In fact, several small coffee roasters don't even roast or offer decaffeinated coffee in their line-up. The reason for this is that decaffeinated, unroasted coffee beans start off almost brown in color rather than green. This makes it difficult for the roasters to control them, since they respond inconsistently and exaggeratedly to heat applied to them during roasting. Decaffeinated beans tend to run hotter in the roaster and require heat introduced later in the roast than caffeinated beans. Furthermore, they have less moisture content, which causes them to roast faster. So, you are dealing with an unroasted “green” bean that tends to roast darker and faster than caffeinated beans.

Sourced from Decaffeination 101: Four Ways to Decaffeinate Coffee (coffeeconfidential.org)