Decaf CoffeesCaffeine constitutes from 1% to 1.5% of the Arabica species coffee bean. For a coffee to be called decaffeinated in the United States, at least 97% of its caffeine must be removed.
Decaffeination removes all the waxes which protect the raw coffee beans, an added benefit for those whose digestive systems are irritated by these waxes.
There are three types of decaffeination:
1. Chemical solvents
2. Supercritical gases
3. Water and caffeine-free extracts
Chemical solvents: First the coffee is steamed, swelling the beans and making extraction easier. Then the coffee is repeatedly rinsed with a solvent at a temperature close to the solvent's boiling point. The better the solvent, the more the caffeine is removed selectively. After the caffeine-laden solvent is drained away, the beans are thoroughly steamed a second time to remove the solvent. The two solvents in use are methylene chloride and ethyl acetate.
Ethyl Acetate is a compound found in many fruits and is thus referred to as a natural process. Its use, however, requires more contact time with the coffee than methylene chloride, and its boiling point is substantially higher. I have not liked any ethyl-acetate-decaffeinated coffees I have tried; coffee flavor is, in my experience, quite radically altered and unpleasant.
Methylene chloride is the most selective solvent, and its boiling point is a mere 104° F, allowing gentler extraction and leaving by far the purest coffee flavor of any decaffeination process. The FDA allows 10 parts per million (ppm) of methylene chloride in food products; while residue in our decaf is below 2 ppm, it is further dramatically reduced from barely-detectible to zero after roasting, where temperatures exceed 400° F. Coffee flavor can be very good.
Supercritical gases: The gas used is carbon dioxide, a natural ingredient of roasted coffee.
Carbon dioxide: After being softened by steam, the coffee beans are immersed in carbon dioxide at high temperature and pressure. In this super-critical state, the gas acts like a liquid solvent and penetrates the beans to remove the caffeine. The gas is then separated and can be re-used after separation from the caffeine through charcoal or evaporation. Coffee flavor can be very good. I continue to get samples of coffee processed this way cup them regularly.
Swiss Water® and water: A batch of coffee is soaked in hot water until 97% of the caffeine, along with many other substances including flavor compounds, is dissolved. Next the caffeine is extracted from this saturated liquid by means of carbon filters. The leftover solution is then used for the next batch of beans, the principle being that only the caffeine will dissolve in the saturated liquid. While a water-only approach might seem the most natural, the problem has been flavor which was quite compromised - until now! Today Swiss Water® is the best there is - at least with the coffee I tasted. The finest decaf I have ever tasted (June 2006) was made by the Swiss Water process (La Magnolia, Costa Rica).
The future of non-caffeinated coffee: There exist several coffee species in Madagascar which have little to no caffeine. They produce seeds (beans) which are unpalatable, however. Creating successful hybrids by crossing them with the high-quality Arabica-species coffee is singularly difficult, if not impossible. A more likely contender will be genetically modified Arabica plants, being developed in several places around the world, including Hawaii. They could make their appearance in three to five years.
A very recent discovery (announced July 2004) appears to be naturally non-caffeinated Arabica plants growing in Arabica's birthplace, Ethiopia. These plants will be far easier to cross with other Arabica plants. Naturally non-caffeinated coffee is coming! It is only a question of when (over five years from now at least).