COLORIMETRIC DETERMINATION OF LIPID HYDROPEROXIDES IN OILS AND FATS WITH MICROPEROXIDASE

The use of the peroxidase-like activity of microperoxidase for the calorimetric determination of lipid hydroperoxides in oils and fats has been investigated. The principle of the determination is that 4-aminoantipyrine and N,N-diethylaniline are coupled oxidatively by the hydroperoxides through the action of microperoxidase, yielding a violet colour with maximum absorbance at 554 nm. The response of the microperoxidase system is enhanced by the presence of acetonitrile. The method has been successfully applied to the determination of methyl linoleate hydroperoxide, tert-butyl hydroperoxide and the hydroperoxides in oil and fat samples (soybean oil, linseed oil, olive oil, salad oil, butter and lard). The results agreed closely with those obtained by the iodometric method. The proposed method permitted the determination of the hydroperoxides at 0.5-0.05 μmole levels, with the same sensitivity regardless of sample type tested, with satisfactory reproducibility compared with that obtained by the conventional assay methods. © 1990.