“Fish oil 18/12” looks reassuringly specific. It normally refers to approximately 18% EPA and 12% DHA by weight, giving about 300 mg of EPA plus DHA per gram of oil.
That is useful information—but it answers only one purchasing question.
It does not automatically identify the molecular form, confirm oxidative condition, establish contaminant compliance or show that the oil will remain within specification throughout its shelf life. Two suppliers can therefore quote the same 18/12 grade while offering materially different documentation, processing history and quality controls.
Establish the Exact Location Before Discussing the Cause
For a typical 18/12 oil, one gram would theoretically provide:
- • approximately 180 mg EPA;
- • approximately 120 mg DHA;
- • approximately 300 mg combined EPA and DHA.
The remaining oil contains other fatty acids and minor constituents. “1,000 mg fish oil” should therefore not be interpreted as 1,000 mg of omega-3 or EPA plus DHA.
Before comparing offers, buyers should confirm:
- whether EPA and DHA are reported as percentages or mg/g;
- whether the figures are minimum limits or typical values;
- whether total omega-3 is tested separately;
- which analytical method is used;
- whether results are expressed as fatty acids, triglycerides or ethyl esters.
GOED’s analytical guidance allows EPA and DHA results to be expressed in different ways depending on the product form. Results that appear similar may not be directly comparable unless the basis and method are aligned.
Is the Oil TG, rTG or Ethyl Ester?
The 18/12 description does not necessarily tell a buyer how the fatty acids are chemically arranged.
Commercial omega-3 oils may be supplied as:
- natural triglycerides;
- re-esterified triglycerides;
- fatty-acid ethyl esters;
- other defined lipid forms.
Molecular form can affect manufacturing route, specification language, positioning and finished-product documentation. It should not be inferred from the EPA and DHA percentages alone.
Buyers should request the stated form and the analytical evidence supporting it. They should also avoid presenting one form as universally superior: absorption comparisons depend on dose, meal composition, formulation and study design.
A Correct EPA/DHA Result Does Not Prove Freshness
Long-chain polyunsaturated fatty acids are susceptible to oxidation. An oil can meet its EPA and DHA assay while still requiring separate review of its oxidative condition.
Peroxide Value (PV): an indicator of primary oxidation;
p-Anisidine Value (p-AV): an indicator of selected secondary oxidation products;
TOTOX: commonly calculated as 2 × PV + p-AV.
Codex CXS 329-2017 gives reference maximums of 5 meq active oxygen/kg for peroxide value, 20 for anisidine value and 26 for TOTOX for the fish oils to which those criteria apply. These values should not be copied indiscriminately to every lipid matrix, particularly oils with high phospholipid content.
A buyer should verify the actual lot results, methods and testing date—not simply accept “fresh” or “low oxidation” as marketing descriptions.
The Package Becomes Part of the Stability Plan
An acceptable result at release does not guarantee the same result after months of storage. Exposure to oxygen, heat, light and pro-oxidant metals can accelerate deterioration.
The specification review should therefore extend to:
- antioxidant system and declared additives;
- nitrogen flushing or other oxygen controls;
- headspace and container closure;
- packaging material and light protection;
- storage and transport temperature;
- shelf-life evidence for the proposed packaging.
Pharmacopoeial guidance for omega-3-rich fish oil emphasizes airtight, well-filled containers, protection from light and storage under inert gas. PDF
Finished softgels, liquids and emulsions still require their own stability programs. A raw-material COA cannot establish the shelf life of the consumer product.
Contaminants Need Their Own Specification
EPA and DHA results do not describe environmental contaminants.
Depending on the source, destination market and product category, the buyer may need limits and appropriate methods for:
- dioxins and dioxin-like PCBs;
- non-dioxin-like PCBs;
- relevant heavy metals;
- other agreed contaminants or process residues.
“Purified fish oil” is not a substitute for numerical limits and lot-specific evidence. Requirements should be established according to the intended market rather than copied from an unrelated supplier sheet.
Source identity and traceability also matter. Buyers may need the fish species, fishing or production region, processing site, chain-of-custody information and sustainability documentation appropriate to their commercial claims.
What Should an 18/12 Fish Oil RFQ Include?
A useful request for quotation should specify more than “18/12, best price.” Include:
- target EPA, DHA and total omega-3;
- reporting basis and required method;
- triglyceride, re-esterified triglyceride or ethyl-ester form;
- oxidation limits and required lot results;
- contaminant and microbiological requirements;
- antioxidant system;
- packaging size and headspace controls;
- shelf life and storage conditions;
- destination market;
- annual volume;
- required certifications.
This gives suppliers enough information to quote comparable material instead of returning several products that share a name but not a complete specification.
Planning an Omega-3 Product?
SRS Nutrition Express can review available fish-oil and omega-3 options against your target EPA/DHA concentration, molecular form, dosage format, destination market and documentation requirements.
Share the intended serving, capsule or liquid format, annual volume and required quality limits. Where available, SRS can provide specifications, representative COAs and samples for technical and commercial evaluation.
The supplied documentation describes the proposed ingredient. Final approval, finished-product compliance and shelf-life validation remain the responsibility of the buyer, manufacturer and qualified laboratory.
Evidence Boundaries
- An 18/12 description does not establish one universal fish-oil specification.
- EPA and DHA concentration does not demonstrate oxidative condition.
- TOTOX should be interpreted using an appropriate method and oil matrix.
- Raw-material results cannot confirm finished-product stability.
- Codex and voluntary industry values do not replace applicable destination-market requirements.
- Supplier documentation should be connected to the proposed grade and commercial lot.
Recommended Reading
- Fish Oil Is Not the Whole Omega-3 Story: Which Source Fits Your Product?
- COA vs. Full Supplement Ingredient Qualification: What Brands Should Request
- Can One Raw Material Specification Work for Every Finished Product?
References
- Codex Alimentarius Commission. Standard for Fish Oils, CXS 329-2017, as amended.
- Global Organization for EPA and DHA Omega-3s. GOED Technical Guidance Documents: Analytical Methods for EPA and DHA. March 2021.
- Ismail A, Bannenberg G, Rice HB, Schutt E, MacKay D. Oxidation in EPA- and DHA-rich oils: an overview. Lipids in Health and Disease. 2016;15:55. DOI: 10.1186/s12944-016-0224-4.
- European Pharmacopoeia. Fish Oil, Rich in Omega-3 Acids and General Chapter 2.4.29.
- United States Pharmacopeia. General Chapter <401>, Fats and Fixed Oils.
Post time: Oct-30-2026
