| Gateway | Science & Technology | Chat | Search | News |
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

Chemical

 

 

  

SUPERCRITICAL FLUID EXTRACTION USING CARBON DIOXIDE

  

 

The extraction Process

Ø      The extract consists of essential oils (EO), active ingredients, fatty oils, coloring matter, and in general all oil soluble substances.

Ø      The residue consists all other substances that are present in the feed.

Ø      The oil soluble substances are a range of chemicals with different molecular weights. They exhibit a solubility pattern inversely proportional to their molecular weights at any given temperature and pressure. The presence of different organic substituted groups also affects the solubility.

Ø      Lower molecular weight components are extracted faster and have higher solubility in CO2, while higher molecular weight components have a lower solubility and consequently lower extraction rates.

Ø      Once the extract is obtained, it is clarified, and water is separated out and the material is filled in containers. This extract is called the total extract.

Supercritical fractionation

Sometimes there is a need to separate the low boiling essential oils or other active ingredients from the high boiling components of the combined total extract. This can be done using liquid supercritical fractionation column. This is a continuous operation with respect to both the extract and CO2. The bottom end of the fractionator is a mixture of unextracted material. The top section carries the extracted low boiling components along with CO2.

Comparison with other extraction techniques

no

Solvent extraction

SCF extraction

1

Solvent presence is unavoidable. The residual ppm level of the solvent depends on the type of solvent used.

Is totally free of solvents and hence very pure

2

Heavy metal content is also unavoidable and depends on the solvent, the recycle method for the solvent, the source of the raw material, and the material of construction of the contact parts of the machinery.

Totally free of heavy metals since they are not extractable even if they are present in the raw material. No heavy metals are present in CO2 and the equipment

3

Inorganic salt content cannot be avoided, using the same concept as above

Totally free of inorganic salts using the same explanation as above

4

Polar substances get dissolved along with the lipophilic substances from the raw material due to poor selectivity of the solvent. During solvent removal operation, these polar substances form polymers, which lead to dark color of extract and poor flow characteristics. All this renders the extract to look different from the basic components in the raw material and hence it is more of a "pseudo" natural extract.

No such possibility since there is very high selectivity of CO2 and no chance of polar substances forming polymers. In addition the operating temperature is only 40-50 degree Celsius.

5

Both polar as well as non polar colors are extracted

Only non polar colors get extracted

6

Solvent removal requires extra unit operations and hence the cost and recovery of useful material is lower

No extra unit operations needed and yield of useful material is very high

Example-SCF extraction of ginger.

Essential oils (EO) contain two basic ingredients:

Ø      Monoterpenes- non-oxygenated hydrocarbons, which are of little importance as perfumery materials.

Ø      Sesquiterpenes- Oxygenated hydrocarbons which are of high importance as perfumery materials.

The EO's obtained from steam distillation contain only monoterpenes and other hydrolyzed products. Hence they are relatively cheap as well as inferior in quality. The Sesquiterpenes cannot be steam distilled. These can however be easily extracted using SCF extraction and hence the quality of the extract is far superior.

Salient features of SCF extraction:

The extracts are free of the following undesirable components:

Ø      Solvent residues

Ø      Decomposition or hydrolysis products

Ø      Heavy metals

Ø      Inorganic substances

Ø      Polar substances

The extracts are clear, transparent, and contain almost every non-polar ingredient present in the original raw material. The moisture content is also reduced by physical separation.

 

Acknowledgement 

for more information

Web Site: http://www.pioneerherbs.com/
 
1