The decaffeination process
Arabica coffee beans contain 1%–1.5% caffeine, whereas robusta
contains more than 2%. Caffeine is an alkaloid with stimulant properties that
are pleasing to the majority of coffee drinkers, but not to all. Decaffeination
caters for those who for whatever reason do not want the stimulant effect of
caffeine.
The caffeine in the green coffee beans has to be extracted. Different processes
are used. The solvents are water, organic extraction agents or carbonic acid.
The processing steps are vaporization, decaffeination and drying. All these
steps are carried out using the green coffee bean.
First the green coffee is treated with vapour and water to open up the bean
surface and the cell structure to access the crystalline caffeine taken up on
the cell walls. The second step is the extraction of the caffeine by an
extraction agent which has to possess the ability to extract only the caffeine.
The caffeine extraction is not a chemical process but a physical one. No
chemical changes take place. Instead differences in the characteristics of the
extraction agent, which has to absorb the caffeine, and the beans containing
the caffeine, are used. The extraction agent absorbs the caffeine selectively.
Once the extraction agent is saturated with caffeine the next processing step
removes the caffeine and the extraction agent can be used again. This
cycle is repeated until practically all the caffeine is removed from the coffee
bean. Then the wet coffee, from which the caffeine has been removed, is dried
until once again it reaches its normal moisture content. It can then be roasted
as usual.
The following decaffeination agents are allowed in the European Union:
methylene chloride, ethyl acetate, carbon dioxide, and watery coffee extract
from which the caffeine is removed by active carbon. All conventional
decaffeination methods have undergone intensive scientific examination and are
considered safe. In the European Union the absolute caffeine content in
roasted, decaffeinated coffee may not exceed 0.1%, or 0.3% in soluble coffee.
In the United States, 'decaffeinated' is generally taken to mean that the
caffeine content has been reduced by 97%, or to less than 3% of the original
content.