A COLORIMETRIC METHOD FOR THE DETERMINATION OF FAT-PEROXIDES AND ITS APPLICATION IN THE STUDY OF THE KEEPING QUALITY OF MILK POWDERS

Abstract

A colorimetric method based on the oxidation of ferrous to ferric iron and the determination of the latter as ferric thiocyanate has been found suitable for the estimation of fat-peroxides in milk powder. To an acetone extract of milk powder is added a solution consisting of 0.1% of ferrous ammonium sulphate and 0.4% of ammonium thiocyanate in 96% acetone, and the colour is developed by heating. The intensity of the red colour is measured with a Coleman spectrophotometer and is found to bear a close relation to the keeping quality of the milk powder. Peroxide values determined by this method are considerably higher than those obtained by an iodimetric procedure (4).