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6 pages, 5 figures, 5 tables.-- Review article.[EN] Peroxide value and the determination of conjugated dienes by UV absorption at 232 nm are normally applied alternatively for the evaluation of primary oxidation compounds. The objective of this study was to define the\udrelationship between both indexes during oil oxidation in sunflower oils with different degree of unsaturation. The oils studied were conventional sunflower oil (SO) and high oleic sunflower oil (HOSO). For comparative purposes, methyl linoleate, whose hydroperoxides are conjugated diene\udhydroperoxides, was also studied. Samples were oxidized at 40 °C in the dark. In order to accelerate oxidation at 40 °C, the natural antioxidants present in the oils were removed, and a high surface to oil volume ratio (0.8 cm 1) was applied  to guarantee total air availability. Linear regressions with high correlation coefficients between peroxide values and conjugated dienes were found for the three lipid systems studied (0.9988, 0.9991 and 0.9977 for methyl linoleate, SO and HOSO, respectively). Significant differences in the slopes of the lines were found (0.0974, 0.0854 and 0.0503\udfor methyl linoleate, SO and HOSO, respectively), indicating the formation of non-conjugated hydroperoxides from oleic\udacid in the oils, even in the oxidation of SO with a high degree of unsaturation. Consequently, only peroxide value would be reliable for the evaluation of primary oxidation compounds in oils of different degree of unsaturation, unless adequate calibration lines (peroxide value versus conjugated dienes) are applied.[ES] El índice de peróxidos y la medida de dienos conjugados mediante la extinción específica a 232 nm se utilizan alternativamente para la evaluación de compuestos primarios de oxidación en estudios de oxidación de aceites y grasas. El\udobjetivo de este estudio fue definir las relaciones entre ambas medidas en aceites de girasol con diferente grado de insaturación.\udLos aceites estudiados fueron aceite de girasol convencional (SO) y aceite de girasol alto oleico (HOSO). Con fines comparativos, también se estudió el linoleato de metilo, cuyos hidroperóxidos presentan estructura de dienos conjugados. Las muestras fueron oxidadas a 40 °C en la oscuridad. Con el fin de acelerar la oxidación a 40 °C, se eliminaron los antioxidantes naturales de los aceites, y se aplicó una relación superficie/volumen de aceite elevada (0.8 cm 1) para garantizar total disponibilidad de aire. Los resultados obtenidos se ajustaron a regresiones lineales con elevados\udcoeficientes de correlación (0.9988, 0.9991 y 0.9977 para el linoleato de metilo, SO y HOSO, respectivamente). Sin embargo,\udse encontraron diferencias significativas entre las pendientes de las rectas (0.0974, 0.0854 y 0.0503 para el linoleato\udde metilo, SO y HOSO, respectivamente), lo que indica la formación en los aceites de hidroperóxidos no conjugados\udformados a partir del ácido oleico, incluso en el aceite SO, de alto grado de insaturación. En consecuencia, sólo el\udíndice de peróxidos sería un índice de confianza para la evaluación de los hidroperóxidos en estudios de oxidación con\udaceites de diferente grado de insaturación, salvo que se utilicen rectas de calibración adecuadas.This work was funded by Ministerio de Ciencia e\udInnovación (projects AGL 2007-62922 and AGL\ud2007-63647) and Junta de Andalucía.Peer reviewe

Relationship between changes in peroxide value and conjugated dienes during oxidation of sunflower oils with different degree of unsaturation