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.