The Various Ways Decaffeinated Coffee is Produced

Last week I received an e-mail from my friend Veronica asking me how decaffeinated coffee is made. What follows is a description of the process.

According to Wikipedia, decaffeination can be defined as the "act of removing caffeine from coffee beans, mate, cocoa, tea leaves and other caffeine-containing materials." In the case of coffee, the decaffeination process is performed on unroasted, green coffee beans. The actual process however varies; there are several different ways to accomplish it. First the green beans are steamed and then rinsed in a solvent that contains as much of the chemical make-up of coffee beans as possible without also containing caffeine in a soluble form. The process is repeated eight to 12 times until it meets the international standard of being 97 per cent caffeine free. The process however is not without its pitfalls; coffee contains over 400 chemicals that are important to the taste of coffee. This means that no chemical means of decaffeination can take place without affecting the taste of coffee.

There are a number of ways decaffeination can take place. These include the Swiss Water method, the direct method, the indirect method, and a process known as supercritical fluid extraction. The Swiss water method involves soaking a batch of green, unroasted beans in hot water, which releases caffeine into the water. The process is repeated over and over again with a new batch of green beans. The caffeine-rich water is then passed through a filter, which traps the caffeine but allows the water and the coffee solids to pass through. The process is repeated with new coffee beans added to the mix, a process that removes only the caffeine, leaving the flavour relatively intact.

The direct method involves having coffee beans steamed for about 30 minutes. These coffee beans are then rinsed repeatedly with with either methylene chloride or ethyl acetate for approximately 10 hours. This method is sometimes marketed as being "naturally processed" because ethyl acetate is a naturally occurring chemical that can be derived from fruits or vegetables. In most cases, however, the chemical is synthesized artificially.

The indirect method involves soaking the green beans in hot water for several hours, making what is essentially a pot of coffee. The beans are then removed and either methylene chloride or ethyl acetate is used to remove the caffeine from the coffee-rich water.

Supercritical fluid extraction involves soaking steamed beans in a liquid bath of carbon dioxide at pressures of between 73 to 300 atmospheres. After a thorough soaking, the pressure is reduced, allowing the carbon dioxide is allowed to evaporate, or else the pressurized carbon dioxide is run through either water or charcoal filters, removing the caffeine. This process has the advantage of not using potentially toxic solvents.

A final version of decaffeination is known as the triglyceride process. With this method, the green coffee beans are soaked in a hot water/coffee solution that draws the caffeine to the surface of the bean. The beans are then transferred to another container that contains coffee oils obtained from spent coffee grounds. After several hours at high temperatures, the triglycerides in the oil remove the caffeine from the beans.