Peroxide value

Peroxide value is an analytical parameter that measures the level of primary oxidation in a fat, quantifying peroxides, the first products formed when lipids oxidise, and it is usually expressed in milliequivalents of active oxygen per kilogram of fat (food science literature). A high value indicates the onset of [rancidity](/glossary/rancidity-oxidation) and a loss of quality, so manufacturers use it to check the freshness of incoming fats and oils such as [poultry fat](/glossary/poultry-fat) or [salmon oil](/glossary/salmon-salmon-oil), as well as the stability of the finished product. A useful nuance: the peroxide value does not tell the whole story, because peroxides later break down into secondary compounds, which is why it is often paired with other measures such as the anisidine value or aldehyde assays. For a buyer, the peroxide value does not appear on the label; it belongs to internal quality control. Monitoring it forms part of a broader oxidation-management strategy, alongside antioxidants, packaging such as [modified atmosphere packaging](/glossary/modified-atmosphere-packaging) and date control, ensuring fat quality is maintained from sourcing to the end of shelf life. The marker: the peroxide value is a behind-the-scenes freshness check for fats, an early-warning measure of oxidation rather than a consumer-facing figure, and it is part of the quality machinery described in the [Petipedia glossary](/glossary).

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