Coffee contains around 1,000 different chemical compounds that affect the flavor, aroma, and body of this wonderfully complex elixir. One such compound is caffeine. The astounding complexity of coffee makes separating caffeine from the rest of these compounds an exceptionally difficult task.
In its natural, unroasted (green) state, coffee is always caffeinated. Since caffeine is water-soluble, soaking the unroasted beans in water can remove caffeine from the beans; however, water alone isn’t the best option for decaffeination.
Brewing a whole batch of beans would decaffeinate them, but there’s a good reason twice-brewed beans haven’t caught on. Water is a non-selective solvent, so it will removeall the flavor and aroma compounds along with the caffeine.
For this reason, all decaffeination methods use one of a few special decaffeinating agents to complete the process. These agents separate caffeine from the essential flavor and aroma compounds, so you can savor your cup without getting wired.
There are three main methods of decaffeination used today:
– Natural decaffeination
– CO2 Process
– Swiss Water Process
There are two different types of solvents that can be used in the natural decaffeination process: Methylene Chloride and Ethyl Acetate. Both are naturally-occurring, organic chemicals found in many fruits.
There are also two different techniques for using these decaffeinating agents: soaking and steaming.
In the first method, unroasted beans are soaked in near-boiling water, which extracts all of the beans’ flavor and caffeine.
The extract is separated from the coffee beans and treated with either Methylene Chloride or Ethyl Acetate. The decaffeinating agent binds to the caffeine molecules and is then removed from the coffee extract.
After the caffeine is removed, the original beans are reintroduced to the coffee extract. The beans absorb all the flavor compounds and oils from the extract, giving them all the flavor of the original beans without the caffeine.
Methylene Chloride and Ethyl Acetate are never absorbed by the beans, because both compounds dissipate at 170 degrees—much lower than the ideal temperature for brewing coffee.
In the second method, the unroasted beans are steamed for around thirty minutes. Steaming the beans opens their pores, making them receptive to caffeine solvents.
The steamed beans are then rinsed with either Methylene Chloride or Ethyl Acetate for around ten hours, to remove the caffeine.
Just like the soaking method, the solvents bond with the caffeine molecules and are evaporated from the mixture. The beans are steamed a final time to remove any leftover solvent.
The CO2 (carbon dioxide) method is the most cost-effective decaffeination process; however, it removes more flavor compounds than natural decaffeination or Swiss Water® Process. Due to its low cost, this method is primarily used for decaffeinating large quantities of commercial-grade, less-exotic coffees, often found in grocery stores.
In the CO2 decaffeination process, unroasted beans are soaked in water, then placed in a stainless steel container, called an extraction vessel. The container is sealed and liquid CO2 is added to the coffee at pressures of 1,000 pounds per square inch.
Due to the high temperature and high pressure, the carbon dioxide remains liquid and is able to extract caffeine molecules from the beans. The CO2 dissolves and removes caffeine from the beans, but leaves larger flavor molecules untouched.
The caffeine-laden CO2 is transferred to another container, called an absorption chamber. In this chamber, the pressure is released and the CO2 returns to its gaseous state, leaving the caffeine behind. The now-caffeine-free CO2 is pumped back into a pressurized container for reuse.
Swiss Water® Process:
The Swiss Water® Process is the only common decaffeination method that is completely chemical-free. Coffee beans can only be Swiss Water® certified if they are decaffeinated by the Swiss Water Decaffeinated Coffee Company in Canada.
Like the other methods, it begins by soaking unroasted beans in near-boiling water, which dissolves the caffeine and flavor compounds.
Instead of being treated with a chemical solvent, this liquid is passed through activated charcoal filters. The filters’ pores are sized to capture large caffeine molecules, while letting smaller flavor and oil molecules through.
At this point, there is a tank filled with flavorless, decaffeinated coffee beans and another tank filled with a caffeine-free coffee extract.
This is where the Swiss Water® Process differs from the others. The caffeine-free coffee extract is added to a fresh batch of unroasted beans, heated, and passed through activated charcoal filters.
Since this extract is already saturated with all the flavor and oil compounds from the previous batch of beans, it is unable to remove any of these substances from the new batch—it will only remove caffeine. The result is decaffeination without much flavor loss.
Post by guest blogger Jordan Yonts. Jordan Yonts is a digital marketing consultant by day, finance student by night, and unskilled amateur chef by late-night. While not consulting, writing, or mistaking powdered sugar for flour, he enjoys discussing and learning about business ethics, theology, economics, and, of course, coffee. You can find him on Google+.