Technological properties of vegetable raw material extraction by liquid carbon dioxide in pre-critical conditions

Processing of the vegetable raw material with liquid carbon dioxide at pressure up to 70 atmospheres and at temperature up to 30.5⁰C is called pre-critical CO² extraction. In those conditions biologically active substances that are in the vegetable raw material are leached through the cell membranes and go to the liquid phase. Actually, this method of extraction should be considered as a liquid method, as it is analogical in its main principles to extraction in the water-alcohol and water-glycerin solutions or to extraction of raw materials in liquid oils or propylene glycol.

By its nature, liquid CO₂ is, although, enough “soft”, but non-polar solution, and, therefore, as an extragent, has activity analogous to activities of other non-polar solutions. As all well extracting non-polar solutions, liquid CO₂ at the pre-critical conditions can extract all the biologically active substances that present en biological raw material with the exception of only “heavy polymers”. In these conditions the “depth” of extraction depends only on exposition time, and also on temperature and pressure in extractor. When extracting in pre-critical CO₂, there is no degradation of biologically active substances due to temperature and chemical actions in contrast to chemical non-polar solutions. There is also no need in additional technological methods for separation of the obtained extracts apart of ballast admixtures of the solution that is a consequence of the evaporation of the solutions from the obtained extracts at high temperature and vacuum when the considerable part of volatile (aromatic) fractions are lost.

Only due to continuous separation of the ready products during extraction we can obtain up to nine different in composition and functional purposes biologically active substances, from fractions that contains volatile (aromatic) ethers and finishing with fraction that is formed by fatty acids and lipoid vitamins. At this step during the process of extraction the solvent (liquid CO₂) in the closed volume turns to gaseous form and is totally removed from the obtained extraction fraction.

- In outward appearance the obtained 100% CO₂ extracts are somewhat fluid (depending on fraction) opaque liquids, usually achromatous, with rich odor that is typical for this kind of raw material.

Conclusions:

1. At the pre-critical CO₂ extraction the extracts with a predetermined preparation composition can be obtained.
2. Pre-critical CO₂ extracts do not have ballast substances and residues of organic solvents, that is, they belong to the “absolute” class by their characteristics.
3. Most of the substances that form pre-critical CO₂ extracts ideally mix with oils, alcohol, propylene glycol and do not induce lamination in emulsions and gels.
4. Pre-critical CO₂ extracts contain only natural biologically active substances that have not been exposed to temperature and chemical actions.

Due to conditions of extraction (absence of oxygen and relatively high pressure) pre-critical CO₂ extracts are completely refined of different types of possible microbiological contamination that allows keeping them in hermetically sealed containers at normal room temperature at least 24 months.

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