Understand what PV, AV and TOTOX reveal about fish-oil oxidation, why their results should be read together, and how to compare lot-specific analyses against use-specific limits.
Peroxide value (PV), anisidine value (AV) and TOTOX are complementary measures used to describe different parts of fish-oil oxidation. PV reflects primary oxidation products, AV reflects certain secondary products, and TOTOX combines the two results. Comparing all three gives a more informative view than relying on a single number—but they do not describe every aspect of oil quality.
Oxidation develops through chemical reactions that can change the oil over time. Because primary products can break down into secondary products, a low PV on its own does not always mean oxidation has been minimal. The interpretation depends on the full set of results, the analytical method and the oil’s intended use.
PV estimates the concentration of peroxides, especially hydroperoxides, formed during early oxidation. It is commonly reported as milliequivalents of active oxygen per kilogram of oil. A higher result indicates more of these primary oxidation products were present in the tested sample.
PV is useful, but it is not a complete history of the oil. Peroxides can decompose as oxidation continues, so PV may decline even while secondary oxidation products accumulate. This is why a PV result should be read alongside AV and in the context of the sample and test method, rather than treated as a stand-alone freshness score.
AV, usually determined with a p-anisidine method, responds to certain aldehydic compounds formed as oxidation progresses. It can add information that PV misses when primary peroxides have started to break down. Like PV, it measures a defined group of chemical indicators—not every oxidation product or every sensory change.
AV results can be affected by the analytical method and characteristics of the sample. When comparing offers or lots, make sure the method is stated and consistent. A number without its method and reporting basis is difficult to evaluate against a specification or another laboratory result.
TOTOX is commonly calculated as 2 × PV + AV. It gives a combined indicator that weights PV twice and adds AV, bringing information about primary and certain secondary oxidation products into one figure. The calculation is useful for screening and comparison when the underlying results are available.
A TOTOX figure should not hide its components. Two oils can have the same calculated value but different PV and AV profiles, which may reflect different stages or patterns of oxidation. Buyers should request the individual PV and AV results as well as TOTOX, and verify that the stated formula, methods and units are aligned. TOTOX is not an independent test that captures all oil condition.
A useful lot comparison records PV, AV and calculated TOTOX together with the test methods, units or reporting basis, sample identification and date of analysis. If results are close to a purchasing limit, ask whether the samples were collected and handled comparably; differences in sampling or test procedure can complicate a direct comparison. Also consider any other quality attributes required for the intended application, since oxidation indicators do not establish fatty-acid profile, contaminants, sensory acceptability or overall suitability by themselves.
Do not apply an aquafeed reference value automatically to every fish-oil purchase. Acceptable limits depend on the buyer’s formulation, product use and applicable purchasing or regulatory requirements. The relevant criterion should be established for the specific use and checked against the applicable standard, rather than assumed from a value used in another context.
Before sourcing, define the required form and application, then state which oxidation results and methods your specification expects. For bulk fish oil, the Fish Oil page is the natural next step once those requirements are clear.
PV measures primary oxidation products, especially peroxides, while AV measures certain secondary aldehydic products. They describe different parts of oxidation, so comparing both is more informative than relying on either one alone.
TOTOX is commonly calculated as 2 × PV + AV. Request the underlying PV and AV results too, since the combined figure can conceal different profiles and depends on comparable methods and reporting.
No universal limit should be assumed. The applicable acceptance criteria depend on the intended use and relevant purchasing or regulatory requirements. Verify the criteria for the specific application, including aquafeed, rather than transferring a reference value from another context.
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