How to Extract Fish Oil: Methods and Techniques Explained
Fish oil is extracted from fish tissues and is rich in omega-3 polyunsaturated fatty acids (such as EPA and DHA), which are beneficial to human health. It offers numerous health benefits, including regulating blood lipids, protecting the cardiovascular system, and reducing inflammation. There are many methods for extracting fish oil, ranging from traditional processes to modern high-tech techniques, each with its own advantages and disadvantages. Below are the main methods and detailed steps for fish oil extraction.
Fish Oil Extraction Methods
1.Physical Extraction Methods
⑴ Pressing Method
Oil is squeezed out of fish tissues using mechanical pressure. This method is simple but has a low extraction rate (only part of the free oil can be extracted). It is suitable for small-scale production and is now less commonly used.
Steps:
Crush raw materials → heat and steam → mechanically press → filter and separate oil.
⑵ Steaming Method
The fish cell structure is broken down by heating to release oil. This method can be divided into direct and indirect steaming.
Steps:
Cut raw materials into pieces → steam at high temperature (80–100°C) → allow to stand for stratification → collect the upper layer of oil.
Disadvantages: High temperatures can lead to oil oxidation, reducing its nutritional value.
2.Chemical Extraction Methods
⑴ Solvent Extraction Method
Organic solvents (such as n-hexane or ethanol) are used to dissolve the oil, which is then recovered through evaporation.
Steps:
Crush raw materials → soak in solvent → filter → distill to recover solvent → obtain crude fish oil.
Advantages: High extraction rate (up to 90% or more).
Disadvantages: Risk of solvent residues, requiring strict purification.
⑵ Light Alkali Hydrolysis Method
Dilute alkali (such as NaOH) is used to break down proteins and release oil. This method is suitable for cod liver oil extraction.
Steps:
Add alkali solution (pH 8–9) to raw materials → hydrolyze → centrifuge to separate → acidify → refine.
3.Biotechnology Methods
Enzymatic Hydrolysis Method
Proteases (such as trypsin or papain) are used to gently hydrolyze proteins and release oil.
Steps:
Homogenize raw materials → add enzyme (40–60°C, pH 7–8) → hydrolyze for 2–4 hours → deactivate enzyme → centrifuge to extract oil.
Advantages: Mild conditions preserve EPA/DHA activity.
Disadvantages: High enzyme cost.
4.High-Tech Extraction Methods
⑴ Supercritical CO₂ Extraction Method
Under high pressure (20–30 MPa) and low temperature (30–50°C), CO₂ is used as a solvent to selectively extract oil.
Steps:
Load raw materials → circulate supercritical CO₂ for extraction → decompress to separate → collect fish oil.
Advantages: No solvent residue, high EPA/DHA purity.
Disadvantages: Expensive equipment.
⑵ Molecular Distillation Method
Under high vacuum (0.1–1 Pa) and low temperature (<100°C), fatty acids are separated based on differences in boiling points.
Steps:
Degum crude fish oil → deacidify → perform multi-stage molecular distillation → collect EPA/DHA fractions.
Advantages: Efficiently concentrates omega-3 (purity can exceed 70%) while avoiding oxidation.
Fish Oil Refining and Enrichment Techniques
The extracted crude fish oil must be further purified to remove impurities (such as cholesterol and heavy metals) and increase EPA/DHA content:
1.Urea Inclusion Method: Uses urea to form complexes with saturated fatty acids, which are then removed by filtration, enriching unsaturated fatty acids.
2.Low-Temperature Crystallization: Cools oil (-20°C) to precipitate high-melting-point lipids, separating liquid unsaturated fatty acids.
3.CO₂ Supercritical Fractionation: Adjusts pressure and temperature to selectively separate different fatty acid components.
Precautions for Fish Oil Extraction
1.Raw Material Selection: Deep-sea fish (such as salmon and sardines) have higher EPA/DHA content.
2.Antioxidant Treatment: The extraction process should involve nitrogen flushing or vitamin E addition to prevent oxidation.
3.Purity Testing: High-quality fish oil should have an omega-3 purity of ≥60%, verified by GC or HPLC analysis.
Industrial-scale fish oil extraction primarily relies on enzymatic hydrolysis and supercritical CO₂ extraction, balancing efficiency and quality. Molecular distillation is the core technology for producing high-purity fish oil. When selecting fish oil products, consider the EPA/DHA content and antioxidant treatment to ensure maximum health benefits.