Green coffee and pure water are loaded together into a stirred tank extractor. This mixture is heated to the temperature set to start the extraction process. Water is not a selective solvent to extract only caffeine from coffee beans. Indeed, the water extracts almost all water soluble substances from coffee and the solution obtained is composed by coffee flavours and caffeine. This solution continuously flows and passes through a bed of special activated carbons with selectivity towards caffeine and its molecules are captured. The solution now deprived from the alkaloid, but still rich of coffee aromas, is sent back, favouring again the extraction of caffeine and inhibiting the extraction of flavourings. This process has a variable length depending on the amount to be extracted. After this stage, the residual aqueous solution is concentrated to suitable conditions without the caffeine. When a certain concentration of flavours in the solution is reached, the reincorporation phase begins. This stage consists in putting the coffee in contact with the concentrated solution in suitable conditions to facilitate penetration of the flavouring in the coffee bean, thus reintroducing the flavour extracted beforehand. The coffee is then dried and cooled. Finally the coffee is bagged as per customers’ specifications.
The water decaffeination process takes place in the Demus S.p.A plant, within which also takes place the decaffeination with dichloromethane. The plant was built in order to minimize the interference between the two separate methods of decaffeination.
The water decaffeinated coffee appears dark, almost black. Some coffee beans are slightly chipped due to the loss of the shoot, because of the prolonged contact with hot water. Decaf is mechanically more delicate than non decaf, thus a bit more fragile and degrades from an organoleptic point of view faster than decaffeinated obtained with other methods.
Water decaffeinated coffee roasting is different from the roasting of regular coffees and other decaffeinated coffees: to obtain a product with good organoleptic characteristics in the cup, we suggest a slow roasting, starting at a lower temperature than that used for the decaffeinated with dichloromethane, with the aim to obtain a homogeneous outcome.
The roasting curves should be recalibrated according to the new product.
Size coffee batch processing: around 2.600 kg
Coffee qualities: arabicas, blends 100% arabicas, blends with robustas ≤ 30%
Residual caffeine in the bean: ≤ 0,1 %
Residual humidity in the bean: ≤ 11%
Weight loss after processing: 8% arabicas, 10% blends with robustas (estimate)