Coffee naturally contains the active supplement caffeine. The stimulating power of
coffee is as well known as the outstanding taste. A lot of people appreciate this
stimulating power, but there are some people that do not handle caffeine so well or do not
like the stimulating effect every time of the day. For them there is decaffeinated coffee
on the market. This decaffeinated coffee lacks the stimulating power of caffeine.
Normal coffee beans contain between 0.8 percent and 2.5 percent caffeine depending on
origin and variety. Decaffeinated coffee is not entirely caffeine-free. In European
Community (EC) countries, roasted decaffeinated coffee may contain a caffeine residue of
0.1 percent and coffee extract 0.3 percent.
To make coffee caffeine free, the stimulating supplement needs to be derived from the
beans. Since coffee develops most of its flavour during roasting, the caffeine is
extracted from the raw green coffee beans. Various methods exist to achieve this, of which
the water-carbon (H2O/C) and dichloromethane (commonly known as DCM) methods are the most
used. Both of these techniques extract the caffeine with a caffeine-selective solvent,
which therefore leaves the other substances in the bean. Modern decaffeinating methods
have no effect upon the flavour and aroma of the coffee. Good decaffeinated coffee
therefore tastes almost the same as coffee containing caffeine.
This process uses water (H2O) as a solvent. The green beans are rinsed with water
for a long period, during which time the caffeine dissolves into the water. The water,
with its dissolved caffeine, is then pumped through an active carbon (C) filter which
absorbs the caffeine. The decaffeinated beans are dried using warm air and then cooled
with cold air. They are then roasted, ground and packed in the usual way. The water is
re-used for the decaffeination process.
This method employs dichloromethane (DCM) as a solvent and has been developed to
suit the requirements of the out of home industry. The green beans are moistened with
water in order to make the surface of the bean porous, and soaked in the solvent for 30
minutes. This is repeated several times. The beans are removed from the solvent once the
caffeine has dissolved. They are then steamed for some time in order to remove any
remaining solvent. Afterwards the beans are dried using warm air, then cooled with cold
air. They are roasted, ground and packed in the usual way. The dichloromethane is reused
for further decaffeinating.
source: Douwe Egberts