Being Supercritical Is Good

Fish oil can be extracted from fish using a couple of different methods. The most common is called molecular distillation. The most OPTIMAL is called supercritical CO2.


What is molecular distillation?

Molecular distillation is an extraction process that uses a vacuum system (low pressure, high heat) to evaporate specific molecules. In this case, we are referring to EPA and DHA, the two key components of fish oil. As heavier contaminants generally do not vaporize well, they remain in the original, non-distilled material. However, contaminants are not completely removed, so further refining is necessary. Molecular distillation uses temperatures of between 140-160 °C, resulting in greater oxidative damage to the oil, measured as TOTOX (total oxidation value).

The ability of molecular distillation to concentrate oils (for example, to create a high EPA final product) is limited, requiring multiple runs of the oil through the distillation process, with consequent repeat exposure to high temperatures. That’s not good. Molecular distillation is suitable for mid-range concentrates, but not ideal for highly concentrated oils.

What is supercritical CO2?

Supercritical CO2 is becoming an increasingly important solvent for oils as well as for herbal distillates and pharmaceuticals. Supercritical CO2 is becoming recognized as a “green” solvent, because of its low toxicity and environmental impact. The term “supercritical CO2” refers to carbon dioxide in its fluid state. When held at its critical temperature and pressure (31.1°C and 72.9 atm), CO2 adopts characteristics between that of a gas and a liquid.

Supercritical CO2 extraction uses compressed or “supercritical” CO2 at very low temperatures (35-50 °C) to gently separate individual fatty acids through column chromatography. The solubility of various substances in supercritical CO2 vary with pressure, allowing for a very selective extraction process, ideal for creating highly purified, highly concentrated extracts.

Supercritical CO2 extraction uses column chromatography with stationary and mobile phases to separate, identify, and quantify compounds as they move through the column. In addition to highly effective concentration, this process allows for the most efficient removal of contaminants including dioxins, furans, PCBs, and heavy metals. Due to the very low temperatures used, there is minimal damage to the oil, and the resultant product has very low TOTOX values. It beats out molecular distillation on all fronts.

Here are the key differences of extraction summarized.


Molecular Distillation

Supercritical CO2

High Quality

High EPA


Low Contaminants


Low Temperature