Determination of Unoxidized Tocopherols in Milk Fat

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Abstract
The procedure was developed to follow tocopherol degradation in oxidizing milk fat. It combines saponification (in the presence of pyrogallol) to destroy tocoquinones and essentially all fat peroxides, chromatography on SnCl2 + HCl-treated Floridin (Kjolhede) to remove carotenoids, possible residual peroxides, steroids, etc., and color development in benzene-ethanol with ferric chloride and bipyridyl in acetic acid solution (Devlin and Mattill). Pyrogallol addition prevented tocopherol destruction during saponification and was superior to saponification under nitrogen. Complete saponification was effected by using 17 ml of 3.5 N KOH/10 g fat. If the saponification step was eliminated, the treated Floridin column reduced tocopheryl-p-quinones but not tocopheryl-o-quinones. The former were similarly reduced by the Quaife and Biehler hydrogenation procedure. Reduced compounds are measured as tocopherols.