In an Arabica coffee the caffeine is contained on average 1.2 to 1.5%, while in a Robusta coffee is present from 2% to 4%.
The decaffeinated coffee is a coffee to which has been removed, by means of a technological process, the caffeine contained in it. Subsequently to the decaffeination process the residual content of allowed caffeine must be not more than 0.1% by weight on the dry product.
The decaffeination of green coffee is obtained with the use of different extraction processes, which differ from each other mainly by the extracting substance used.
All processes involve some common steps.
In all cases the green coffee is wet in large tanks filled with water and in the presence of steam, so that the beans swell and extraction of caffeine is easier through the widened fibers.
At this point a solvent extracts the caffeine that is transported out of the grain.
The most common system uses as a solvent the dichloromethane, highly volatile (evaporates at 40 °), very selective so that the aroma of the coffee remains intact.
Another system, uses water as solvent, however, theis method has the limit to be little selective and therefore, reduces and changes the coffee aromatic range.
A third process is known as CO2 extraction.
At very high pressures and temperatures, the carbon dioxide assumes an intermediate state between liquid and gas and acquires characteristics of extreme selectivity and speed of extraction of caffeine to which it becomes a product suitable for the removal of caffeine from coffee.
It is a refined method but also expensive for the type of equipment that must be used and then suitable for large volumes.
With this system the organoleptic characteristics and the aroma remains intact and the coffee you get, keeps its original qualities.