220.127.116.11. Advantages and disadvantages of extraction with supercritical CO2
The advantages in using supercritical CO2 are largely of a “health and safety” and environmental nature and relate to increased unease about the presence of organic solvent residues in material for human consumption. However it is also well established in certain applications that the extracts obtained are more acceptable to taste panels than extracts obtained in other ways. This in turn probably relates to the closeness to which the extracted flavour resembles that in the original plant.Advantages can be summarised as follows:
It can be easily recycled
Chemically inert. (However Lorn (1988), notes the presence of some acetates on the raspberry extract, obtained with supercritical CO2)
Has good solvent characteristics for non-polar and slightly polar solutes.
It is a “natural” substance, present in mineral waters and part of the life cycle
It is easily removed from the product
The dissolving power and selectively can be controlled by selection of suitable pressure/temperature combination
It has a convenient critical temperature (31.04ºC). This enables extractions to be carried out at comparatively low temperature (often as low as 40 or 50ºC), decreasing the risk of damage of thermalabile compounds.
Most of the volatile components, which tend to be lost in hydrodistillation, are present in the supercritical extracts [Martinez de La Ossa et al. (1991) and Vardag and Korner (1995)]. Partly because of this, extracts obtained in this way tend to have flavour and taste, which are well liked by tasty panels.
Extraction of natural raw material with supercritical CO2, allows the obtaining of extracts which flavour and taste are perfectly respected and reproducible
The supercritical fluid ability to vaporise non-volatile components (at moderate temperatures) reduces the r energy spent, when comparing to distillation.
Once the pressure excess in the equipment prevents oxygen entry while extraction occurs, oxidation reactions don’t happen
The number of solvents possible to be used on supercritical extraction is superior of classic organic solvents
Supercritical fluids have a superior selectivity although they have an inferior solvent power than classic organic solvents
Many examples of the extraction of aromatic herbs with liquid and with supercritical carbon dioxide are giving by Moyler (1984, 1994), Naik et al. (1989) and Meyer-Warnod (1984). In addition, the table below lists literature references to the extraction of several herbs and spices using liquid or supercritical carbon dioxide.
|Rosmarinus officinalis||30 MPa/35ºC/60 minTateo and Fellin, 1988|
30 MPa/45ºC/60 min
|10 MPa/40ºC||Reverchon and Senatore, 1992|
|Liquid CO2||Moyler, 1993|
|Vanilla||10-13 MPa/35-38ºC||Nguyen et al., 1991|
|Liquid CO2||Moyler, 1993|
|Coriandrum sativum L. (Fruits)||9 MPa/40ºC|
|Kerrola and Kallio, 1993|
|Coriandrum sativum L.||5.7 MPa/20ºC|
|Machado et al. 1993|
|Coriandrum sativum L.||12,5 MPa/35ºC|
|Lopes Cardoso, 1992|
|Mentha piperita||8-13 MPa/33-37ºC/4 h||Barton et al., 1992|
|Juniperus communis||Liquid CO2||Moyler, 1993|
|Ocotea caesia||8MPa/40º C/40 min||Janete et al.,1994|
Vilegas et al.,1994
|Piper nigrum L.||6.35-7.35 MPa/16-20ºC||Ferreira et al., 1993|
|9 MPa/50ºC||Reverchon et al., 1994|
|Humulus lupulus L.||Liquid CO2||Moyler, 1993|
|Syzygium aromaticum L.||Liquid CO2||Moyler, 1993|
|Thymus vulgaris||20 MPa/54ºC/30 min||Hartonen et al., 1992|
|Liquide CO2||Moyler, 1994|