Determination of Peroxide Values of Some Fixed Oils by Using the mFOX Method

ABSTRACT The peroxide value is a useful indicator of the extent of oxidation of lipids, fats, and oils. The oxidation of food lipids is undesirable due to off-flavors, toxins, and loss of fat-soluble vitamins. Some fixed oils like walnut, hazelnut, wheat germ, sesame, nettle seed, grape seed, and St. John's oil are used in food, cosmetics, and medicine. In addition, the analysis of the peroxide content of oil samples is a very analytical task because high peroxide levels in oils have been a threat to human health. In this investigation, the determination of the peroxide values was performed after opening bottles of different commercial oil samples and after 1 month of storage at room temperature. The peroxide values of fixed oils were analyzed by the improved ferrous oxidation–xylenol orange (mFOX) method. The method is based on the absorbance measurements at 650 nm for colored complex of ferric ions formed by the oxidation of ferrous ions with the reaction of peroxides in the presence of xylenol orange (3,3′-bis [N,N′-di{carboxymethyl}-aminomethyl]-o-cresolsulfonephthalein). A standard curve was used for the mathematical estimation of the peroxide amount of fixed oils. A good coincidence was reported for the experimental results. KEYWORDS: determinationfixed oilsmFOX methodperoxide values Acknowledgments This was an invited paper for a special issue on the 12th National Spectroscopy Congress, Turkey, with International Participation, May 18–22, 2011, at Ankara University, ÖRSEM campus, Side-Antalya, Turkey. The issue was edited by Erdal Dinç, Ankara University, Faculty of Pharmacy, Department of Analytical Chemistry. Notes SE(m), standard error of slope of calibration curve; SE(n), standard error of intercept of calibration curve; SE(r), standard error of correlation coefficient of calibration curve; LOD, limit of detection; LOQ, limit of quantitation. a Values represent the averages of triplicate analysis ± standard deviations. b The period of oil stored at room temperature after manufactured and sealed in a bottle. c One month passed after opening the oil of the same bottle, stored at room temperature. d Two months passed after opening the oil of the same bottle, stored at room temperature. SS, sum of squares; df, degree of freedom, MS, mean squares. This was an invited paper for a special issue on the 12th National Spectroscopy Congress, Turkey, with International Participation, May 18–22, 2011, at Ankara University, ÖRSEM campus, Side-Antalya, Turkey. The issue was edited by Erdal Dinç, Ankara University, Faculty of Pharmacy, Department of Analytical Chemistry.