Supercritical carbon dioxide isn’t only a efficient solvent for apolar compounds, in fact, if it’s combined with fluid modifiers like water, it becomes a very efficient solvent also for medium polar and polar substances (caffeine for coffee decaffeination).The extraction efficiency than conventional technologies based on chemical solvents is achieved by the following features offered by supercritical CO2:
- Increase Of Mass’ Transport for the Zero Superficial Tension Effect, with correlated advantages in the extractive efficiency and in the duration of the extractions (minutes vs. hours);
- With a minimum modulation of temperature and pressure in the process, the Solvent Properties are modified in an important way;
Totally Miscible like gasses;
- Low Viscosity, Eco-Friendly and green solvent, Not Inflammable, Inert and Not Toxic;
- High Diffusivity and so it can increase the extractive kinetics;
The Co-Solvents (water, ethanol) can further modify the solvent proprieties;
The relatively low temperatures of extraction help the Conservation of volatile compounds;
- This process is not influenced by the Oxidation: the extraction vessel, full of supercritical CO2, is an inert space for the oxidation process also at high temperature (50-70 °C);
- Antibacterial and so the final extracts are high quality products, for a microbiology point of view;
- Cheap: it’s common in the atmosphere (0,04% and this value is still raising in this years) and it’s concentrated in a pure solution (99,9% of CO2, gas state,20-25 bar), simply available in safety cylinders bottles.
During the process the CO2 is continually Recycled and this reduce the primary costs of extraction. At the same time, the small quantity of solvent lost during the process, and so released in the atmosphere, doesn’t increase global CO2 emissions, because the same CO2 was concentrated from the atmosphere in cylinders;
- If it was used a polar Co-Solvent (like water and ethanol) for the extraction of polar or medium polar chemical compounds, the extracted substances are easily isolated with the evaporation of the co-solvent.