In the lab
Decaffeination with natural liquid carbon dioxide - Behind the doors of the CR3 plant
César MAGAÑA | 2019-10-22
Decaffeination plant report (1/4).
CR3 is headquartered in Bremen, Germany. It operates the only facility in the world that uses subcritical CO2 to decaffeinate coffee. Managing Director Jan Schwital, Specialty Manager Joshua Ruiz and Head of Quality Oliver Suesse-Herrmann welcomed César this summer for a visit and explanation of this decaffeination method, unique in the profession. Here, we share their decaffeination experience and clarify certain aspects of their innovative decaffeination technology.
A little physics : what is the difference between supercritical and subcritical?
In nature, matter is found in three different forms, depending on the surrounding temperature and pressure conditions: solid, liquid and gas. But there are also other more exotic states which apply only to certain materials under certain conditions.
Carbon dioxide (CO2) is called pure gas because it's composed of a single molecule. Under atmospheric conditions (1,013 bars at sea level and a temperature of 15°C), CO2 exists in a gaseous state. The air that we breathe also contains 0.04% CO2.
It is however possible to change a state of a pure gas by altering its surrounding pressure and temperature conditions. For example, we can change CO2 from a gaseous to a liquid state by creating specific conditions. This is called liquefaction. And the process is reversible, meaning that the CO2 can also return to its original state, which is called vaporisation.
There is also an additional state, called the supercritical state. In this state, CO2 becomes a liquid while possessing the physical and chemical properties of a gas. This in an in-between state that is possible only at a pressure above 73.8 bars (critical pressure) and a temperature more than 31°C (critical temperature). Extraction with supercritical CO2 is a well-established technology also used for the decaffeination of coffee.
Graphical presentation of supercritical CO2
Under these specific conditions, CO2 has unique properties, between those of a gas and a liquid.
CR3 uses liquid CO2 under subcritical conditions
This is where CR3 has been so innovative. Unlike other plants, CR3 uses a different state called the subcritical state. As opposed to supercritical CO2, subcritical CO2 requires lower temperature and pressure conditions (23°C and a pressure between 70 and 80 bars), which is a major advantage for us as coffee producers because it is less detrimental to the other components of green coffee, while preserving an optimum aromatic profile.
Graphical presentation of subcritical CO2
According to Jan Schwital, “liquid carbon dioxide has excellent properties in terms of selectivity for caffeine and hence quality. The high selectivity for caffeine comes at the cost of low solvency power resultin in long extraction times (up to 7 days). However if you define the quality of a process by the least change between the green coffee before and after processing, we do believe that our process offers the best result and that the quality speaks for itself."
View of CR3 company
View of CR3 company
A 4-step process
1 Steaming. First, the green coffee is placed in a tank and is treated with water vapour. This step is carried out prior to decaffeination and prepares the coffee beans by making them swell and more permeable for the extraction with the liquid carbon dioxide.
2 The beans are then placed in contact with liquid CO2 under subcritical conditions. During extraction the liquid CO2 continuously draws caffeine out of the coffee beans. The caffeine is dissolved in the liquid CO2. Because CO2 has a very high selectivity for caffeine practically no other components are dissolved, resulting in a very high quality.
3 The flow of liquid CO2 then carries the caffeine into a separate tank where the CO2 is evaporated into a gaseous state. Consequently, the CO2 loses its affinity for caffeine. The purified CO2 is then transformed back into a liquid state (by compression) and is then returned to the decaffeination tank to begin a new cycle.
4 Once a caffeine content of less than 0.08% is reached (under European regulations, the maximum authorised caffeine content for decaffeinated coffees is 0.1%), the beans are removed and dried using vacuum and warm air bed drying.
2 The beans are then placed in contact with liquid CO2 under subcritical conditions. During extraction the liquid CO2 continuously draws caffeine out of the coffee beans. The caffeine is dissolved in the liquid CO2. Because CO2 has a very high selectivity for caffeine practically no other components are dissolved, resulting in a very high quality.
3 The flow of liquid CO2 then carries the caffeine into a separate tank where the CO2 is evaporated into a gaseous state. Consequently, the CO2 loses its affinity for caffeine. The purified CO2 is then transformed back into a liquid state (by compression) and is then returned to the decaffeination tank to begin a new cycle.
4 Once a caffeine content of less than 0.08% is reached (under European regulations, the maximum authorised caffeine content for decaffeinated coffees is 0.1%), the beans are removed and dried using vacuum and warm air bed drying.
Decaffeinated coffee process in CR3
The avantages of this process
+ The main advantages of this process are the high selectivity of natural carbon dioxide and the relatively low temperature exposure during the process, thereby preserving not only the coffee will remain unaltered, which is especially beneficial to high-grade Arabica coffees.
+ Chemical free - the process uses only potable water and natural carbon dioxide, so there are no synthetic compounds, meaning it can be used for the decaffeination of certified organic coffee.
+ Although an energy-intensive process, this is offset by optimised energy efficiency. CR3 uses natural gas and generates electrical energy in a high efficiency coupled heat and power system to minimize power consumption and emissions.
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Tank of decafeination – CR3, Bremen, Germany
Report: Belco field study of decaffeination processes
Decaffeinated coffees are attracting interest from a new public, more mindful of cup quality, which is something that many decaffeination professionals have clearly understood. At Belco, we place a high priority on integrity, and are firmly commited to supplying quality green coffees. This is why we chose to study the different decaffeination technologies more closely, in order to choose the one that best meets our quality standards. As a result of this research, we are today able to answer many questions and concerns and put paid to some preconceived ideas about “decaf” coffee.
We currently work with four partners, who decaffeinate our coffees using three different processes. César, our quality manager, has travelled the world to find out exactly what each decaffeination process involves. From Canada to Germany, via Colombia and Mexico, click on the links below to read our reports :
