How to compare salmon oil fatty-acid and oxidation specifications

Start with the basis of the EPA and DHA values

EPA and DHA figures are useful only when you know what the percentage describes. A result may express each fatty acid as a percentage of total fatty acids, or as a percentage of the whole oil. Those denominators are not interchangeable: total fatty acids describe the relative fatty-acid profile, while whole-oil values relate the amount to the oil itself.

When comparing salmon oil offers, read the unit and denominator next to each result rather than comparing percentages in isolation. Ask whether EPA and DHA are reported individually, whether the figures are percentages or another unit, and what analytical method and reporting basis were used. If one specification uses a fatty-acid profile and another uses whole-oil content, the numbers cannot be treated as directly equivalent without a clear, appropriate conversion basis.

A useful specification identifies the product grade and states the basis plainly. It should also show whether EPA and DHA are separate results or combined. A combined figure can obscure a difference in the balance between the two fatty acids, which may matter when a formulation sets individual targets.

Read peroxide and anisidine values as different measurements

Peroxide value (PV) measures primary oxidation products, principally peroxides formed as oils oxidize. Anisidine value (AV) measures certain secondary oxidation products, including aldehydes. Because they reflect different stages or products of oxidation, one result does not stand in for the other.

A low PV on its own does not provide a complete picture of oxidation: peroxide compounds can break down as oxidation progresses, while secondary products remain relevant. Conversely, AV alone does not show the primary oxidation result. Read both values together, alongside their units, test methods and sample context, rather than treating either as a universal freshness score.

The test method matters because results are meaningful in relation to how they were produced. When two offers report oxidation values, compare the method and reporting basis as well as the number. If those details differ or are missing, treat the results as non-equivalent until the analytical basis is clarified.

Use ToTox as a combined indicator, not a replacement for its components

ToTox is commonly calculated as twice the peroxide value plus the anisidine value: ToTox = 2 × PV + AV. It brings information about primary and secondary oxidation into one figure, but it does not erase the distinction between the two underlying tests.

For a fair comparison, check that the PV and AV used in the calculation come from compatible analytical results and that the ToTox calculation is identified. Review the component values too. Two oils could have the same combined result while differing in the balance of primary and secondary oxidation products.

Do not compare a supplier’s reported ToTox figure with a calculated value unless the inputs, units and methods are clear. A specification should make it possible to understand both the summary indicator and the measurements behind it.

Match criteria to the salmon oil’s intended grade and use

Reference criteria used for oils intended for human consumption are not automatically the requirements for salmon oil sold into feed or pet-food applications. The applicable specification depends on the product grade, intended use and buyer’s quality program. A familiar human-consumption reference value should not be presented as a universal salmon oil limit.

For a sourcing comparison, first define the intended market and the required grade. Then compare the same set of fields across offers: EPA and DHA with their denominator and units; PV and AV with methods and units; and ToTox with its calculation basis. If a buyer has a required criterion, state it as a purchase requirement rather than assuming it applies to every grade.

The date and context of the analysis also matter. A test result describes the sample at the time it was analyzed; it does not by itself establish the condition of a later shipment. For a purchasing decision, align the analysis date, lot identification and product grade with the material being offered.

Build a comparable specification before buying

A practical comparison sheet should give each result its own row or field, with the value, unit, denominator where relevant, analytical method and sample or analysis date. Keep EPA and DHA separate from oxidation measures, and keep PV, AV and ToTox visible as distinct fields. This makes missing context easier to spot than a single headline claim about omega-3 content or freshness.

Before requesting a quote, define the salmon oil grade and the analytical requirements that matter for your application. If your formulation depends on a particular EPA-to-DHA profile or oxidation criteria, provide those requirements with the intended use. Exact limits, methods and supporting lot documentation need to match the specific offer; they should not be inferred from a general reference.

For buyers sourcing against a defined analysis, see the [Salmon Oil ingredient page](/ingredients/salmon-oil) and include the required analytical basis in your inquiry.

Common questions.