This process was first discovered by a scientist called Kurt Zosel at the Max Planck Institute for Coal Research in 1967 as he was looking at new ways of separating mixtures of substances. In 1988, a German decaffeination company called CR3 developed this process for decaffeination whereby natural carbon dioxide (which comes from prehistoric underground lakes) is combined with water to create ‘sub-critical’ conditions which create a highly solvent substance for caffeine in coffee. It is a gentle, natural and organically certified process and the good caffeine selectivity of the carbon dioxide guarantees a high retention level of other coffee components which contribute to taste and aroma. The process is outlined below:
1. The green beans enter a ‘pre-treatment’ vessel where they are cleaned and moistened with water before being brought into contact with pressurised liquid carbon dioxide. When the green coffee beans absorb the water, they expand and the pores are opened resulting in the caffeine molecules becoming mobile.
2. After the water has been added, the beans are then brought into contact with the pressurised liquid carbon dioxide which combines with the water to essentially form sparkling water. The carbon dioxide circulates through the beans and acts like a magnet, drawing out the mobile caffeine molecules.
3. The sparkling water then enters an evaporator which precipitates the caffeine-rich carbon dioxide out of the water. The now caffeine-free water is pumped back into the vessel for a new cycle.
4. This cycle is repeated until the required residual caffeine level is reached. Once this has happened, the circulation of carbon dioxide is stopped and the green beans are discharged into a drier.
5. The decaffeinated coffee is then gently dried until it reaches its original moisture content, after which it is ready for roasting.
