Hydraulic pressing, heat extraction and solvent extraction are traditional methods that are commonly used to extract fish oils. Usage of high temperature, toxic solvents and high degree of oxidation are the major drawbacks of these traditional methods. High temperature degrades heat-sensitive natural compounds, while residual toxic solvents may be present in the final product when used in the extraction process.
Furthermore, because the extraction process requires a significant amount of heat, these traditional methods usually have a greater impact on the environment and there is a risk of toxic solvents leaking into the environment.
To produce concentrated fish oil, molecular distillation is commonly used while a minority of fish oil processed using supercritical CO2 extraction.
Although molecular distillation is a cheap and effective way to purify and concentrate fish oil, heat is a major drawback. Just like light and oxygen, heat is detrimental to omega-3 because it increases oxidation/rancidity. In molecular distillation process, omega-3 oil are repeatedly exposed to high heat. Especially so for fish oils with higher concentration of omega-3. The repeated and prolonged heat exposure could also result in generation of unwanted residues.
Supercritical CO2 extraction is a purification and concentration technology that is fairly new to fish oil market and it is more superior than molecular distillation. Crude fish oil is mixed with liquid CO2. Omega-3 dissolved into the liquid CO2 are then easily separated and concentrated from other fats and cholesterol. This results in pure, odourless and extremely low cholesterol fish oil extract that is free of heavy metals, other toxic contaminants or solvent residues. Since CO2 is recycled, this technology is also environmentally sustainable. With this technology, highly concentrated and pure fish oils can be made without using heat (just above room temperature). Compared to molecular distillation, this technology applies up to 350% lesser heat to the oil. The usage of low temperature prevents thermal stress on the highly temperature-sensitive omega-3 EPA and DHA. This renders supercritical CO2 extraction one of the most suitable technologies for the concentration of polyunsaturated fatty acids.
Comparison between Supercritical CO2 Extraction and Molecular Distillation
In addition to extraction technology, it is very important to use nitrogen in fish oil bottling facility at every stage of processing to minimise exposure to oxygen, which in turn protects the fish oil from oxidative rancidity. Oxidised fish oil is detrimental, it can lead to increased free radical generation in the body, as well as unpalatable fishy smell.
Fish oil processed via supercritical CO2 technology is superior to molecular distillation or traditional extraction method because it does not involve high heat and toxic solvents. The use of nitrogen at every stage of processing is vital to minimize exposure to oxygen, which will protect fish oil from rancidity, as well as fishy smell.