Peroxidewaarde

Peroxidewaarde, commonly abbreviated PV, is a measure of the amount of peroxides and hydroperoxides formed in fats and oils, representing primary oxidation products. It is expressed as milliequivalents of active oxygen per kilogram of sample (meq O2/kg). A low PV indicates little primary oxidation; PV increases as fats oxidize, although the value may decrease later as peroxides decompose to secondary products.

Determination is typically by iodometric titration. A sample is dissolved in an organic solvent mixture, such as acetic acid/chloroform or isooctane, and treated with potassium iodide. Peroxides liberate iodine, which is titrated with sodium thiosulfate using a starch indicator. The peroxide value is calculated from the amount of thiosulfate used, the normality of the titrant, and the sample weight. Standardized procedures exist (for example ISO 3960 and various AOCS methods).

PV is influenced by storage conditions (light, heat, oxygen), metal catalysts, processing conditions, and the presence of antioxidants. In freshly refined oils, PV is typically low; during storage or frying, PV rises as oxidation proceeds. Over longer times, peroxides can break down, causing PV to either stabilize or decline, while secondary oxidation products increase.

Applications include quality control and shelf-life assessment of edible fats and oils, margarines, and processed fat products, as well as use in cosmetics and feed ingredients. PV is a common parameter in the food industry and research to assess freshness and oxidative stability of fats and oils.