Decaf Coffee Secrets
This entry was posted on December 21, 2008.
If you're like us, you might regard decaffeinated coffee as a disturbingly man-made mutation on the bland side of the flavor spectrum. Not that we've ever actually tasted it -- we're working largely from gross assumption here -- but we often get raving reviews of Lavazza's DEK decaffeinated coffee, so our interest was piqued: How is the caffeine removed from the bean, without it losing all it's flavor?
We found that there are three different methods for decaffeinating coffee: Organic solvents, water or carbon dioxide. The roaster often performs each method before they begin the roasting process.
Organic Solvents - Ethyl Acetate or Dichloromethane (DCM)
Decaffeination is performed directly or indirectly, utilizing chemical solvents to remove the caffeine compound. The direct method involves soaking the beans in hot water and the chemical solvent in order to release the caffeine compound into the water. The solvent is removed (taking much of the caffeine with it) and then the beans are put back into the water to reabsorb any flavors they may have lost. In the indirect method, the beans are soaked in the hot water to release the caffeine compound, are removed and then the solvent is put into the water to remove the caffeine, then the decaffeinated water is sprayed on the coffee to reabsorb flavor. While these are cheap methods of decaffeination, both solvents used are considered to have carcinogenic properties.
Often referred to as Swiss Water Process (which is trademarked by Kraft), this chemical-free decaffeination process utilizes a number of steps:
- A starter batch of unroasted beans is soaked in water, which absorbs the caffeine and flavor compounds.
- The caffeine-laden water is passed through carbon filters that remove the caffeine compounds but leave the flavor constituents intact.
- The caffeine-free, coffee-flavored water is used to soak a new batch of beans; as in the beginning of the process, the caffeine leaches into the water -- however, since the water contains as much of the flavor compounds as it can hold, flavor components are not leached from the new batch of beans, so they remain flavorful.
Carbon Dioxide - Lavazza's Preferred Method
As opposed to the first two decaffeination methods, which eliminate caffeine but also some of the flavor, the process using carbon dioxide - which is the same substance used to make beverages fizzy (e.g. sparkling water and soft drinks) - makes it possible to maintain all the aromatic characteristics of coffee. Lavazza uses this method because it's highly selective and avoids the use of any "chemical" solvent. During the first phase of the process, the beans are moistened with steam and/or water until they reach a humidity level of 30-50%. They are then placed in an extraction cylinder, in contact with gas in a "supercritical" condition. This condition is achieved when the temperature and pressure that are reached are such that the gas acquires the characteristics of both a gas and a liquid. Thus, it spreads out like a gas, but since it also has the solvent properties of a liquid, it facilitates the extraction of caffeine. At operating pressure and temperature conditions, the carbon dioxide begins the selective extraction of the caffeine, which will then be separated from the alkaloid by water. The cycle ends with a process to dry the coffee, which is now completely free of caffeine.