Peroxide value colorimetric determination

Peroxide value (POV), 656, 657-64 chromatography, 672 colorimetric determination, 632 mbber and elastomers, 676 Peroxisomes, antioxidant in biological systems, 610, 611 Peroxo complexes... 

Several methods have been introduced which express the degree of oxidation deterioration in terms of hydroperoxides per unit weight of fat. The modified Stamm method (Hamm et at 1965), the most sensitive of the peroxide determinations, is based on the reaction of oxidized fat and 1,5-diphenyl-carbohydrazide to yield a red color. The Lea method (American Oil Chemists Society 1971) depends on the liberation of iodine from potassium iodide, wherein the amount of iodine liberated by the hydroperoxides is used as the measure of the extent of oxidative deterioration. The colorimetric ferric thiocyanate procedure adapted to dairy products by Loftus Hills and Thiel (1946), with modifications by various workers (Pont 1955 Stine et at 1954), involves conversion of the ferrous ion to the ferric state in the presence of ammonium thiocyanate, presumably by the hydroperoxides present, to yield the red pigment ferric thiocyanate. Newstead and Headifen (1981), who reexamined this method, recommend that the extraction of the fat from whole milk powder be carried out in complete darkness to avoid elevated peroxide values. Hamm and Hammond (1967) have shown that the results of these three methods can be interrelated by the use of the proper correction factors. However, those methods based on the direct or indirect determination of hydroperoxides which do not consider previous dismutations of these primary reaction products are not necessarily indicative of the extent of the reaction, nor do they correlate well with the degree of off-flavors in the product (Kliman et at. 1962). 

Iodine, colorimetric determination of amylase using, 689-692 Iodine value, lipid composition canola oil, 474 (table) oil quality indices, 467-469, 475-477 lodometric titration, determination of peroxide value, 518-519 Ionization techniques, in mass... 

Kofakowska, A. and Szybowicz, Z., 1981a, An attempt to fix criteria of rancidity of frozen fish on a basis of colorimetric determination of peroxide value, Chlodnictwo, 16(7IS), 37, (in Pohsh). 

The standard iodometric method for peroxide value requires a sample of 5 g for peroxide values below 10, and about 1 g for higher peroxide values. The sensitivity of this method is about 0.5 meq/kg, and can be improved by determining the iodine starch-end point colorimetrically, or the liberated iodine electrometrically by reduction at a platinum electrode maintained at constant potential. 

The ferric thiocyanate method for peroxide value is based on the oxidation of ferrous to ferric ions, which are determined colorimetrically as ferric thiocyanate. This method is more sensitive and requires a smaller sample (about 0.1 g) than does the iodometric method (Table 5.3). However, the values obtained by the ferric thiocyanate method are higher by a factor of 1.5 to 2 relative to those of the iodometric method. The peroxide values obtained by both methods are of only relative significance. The ferric thiocyanate method is commonly applied to dairy products, which undergo oxidative deterioration at relatively low peroxide values. Other colorimetric methods for peroxide values include the determination of the blue starch-iodine complex in the iodometric method, the red color developed with 1,5-diphenyl-carbohydrazide, the color developed with ferric ions and xylenol orange, ferrous chloride and 2,6-dichlorophenolindophenol, titanium dichloride, and xylenol orange. 

Peroxide value determination, "CSN 580130, part 4 - 1986 747 TAKAGI, ., MITSUNO,Y.,MASUMURA,M. Determination of peroxide value by the colorimetric iodine method with protection of iodide as cadmium complex, "Lipids", (2),147-152 (1978)... 

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