Agriculture Reference
In-Depth Information
Fig. 12.3
Supercritical CO
2
density as a function of pressure and temperature.
1 Extraction time - equates to total kg CO
2
/kg raw material
2
Extractor design
3
Raw material pre-treatment
•
Particle size
•
Particle porosity
•
Bulk density.
Extraction time is largely determined at the design stage of any equipment and the
circulation pumps sized to meet a pre-determined batch extraction time. Extractor
design is also optimised at the same time. Extraction of molecules that have very
limited solubility in supercritical CO
2
can be enhanced by the addition of
entrainers. These are co-solvents added as a percentage of the supercritical CO
2
fl ow prior to the extractor to increase the solvating power of the extraction solvent.
Ethanol is most commonly used as a co-solvent and can be used both to increase
solvent polarity and as a carrier for the subsequent extract. Vanilla beans are
normally extracted in this way to keep the extracted vanillin in solution.
Many commercial fl avour and fragrance raw materials have already been extracted
using liquid or supercritical CO
2
and their composition published together with the
comparative composition with traditional methods of extraction described. Between
2000 and 2010 over 220 new papers were published describing both the essential oil
composition and a broader range of functional molecules such as antioxidants.
Extraction with carbon dioxide produces an extract that will vary in composition
according to the temperature and pressure used and will not produce a product
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