Determination of Lipid Oxidation in Edible Oils by near Infrared Spectroscopy

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Abstract
The relationship between near infrared (NIR) second derivative spectra and lipid oxidation was investigated to develop a method for the determination of lipid oxidation in edible oils by NIR spectroscopy, using peroxide value ( POV) as the index of oxidation. Although several absorption peaks were found in the difference second derivative spectra of oxidised edible oils, the intensity of the peak at 2084 nm only was highly correlated to POV. In the spectra of purified hydroperoxides of methyl oleate and methyl linoleate, the intensity of the peak at 2084 nm was also highly correlated with POV, which demonstrates that the absorption is due to hydroperoxide. In addition, this peak shifted and weakened after reduction of hydroperoxide to hydroxide, which shows the absorption is specific for the hydroperoxyl group. These results suggest that 2084 nm is the key wavelength for lipid peroxide and can be used for the determination of lipid oxidation in edible oils.