Oxidation of Milk Fat Globule Membrane Material. I. Thiobarbituric Acid Reaction as a Measure of Oxidized Flavor in Milk and Model Systems

Abstract

Summary The thiobarbituric acid (TBA) reaction was used for investigating oxidized flavor in model systems containing fat globule membrane material and ascorbic acid. Trichloroacetic acid was used to flocculate the proteins and the TBA reaction was carried out and determined in the filtrate. The method is highly satisfactory in reproducing and measuring rapid oxidation rates in the model system. When applied to milk, lactose was found to contribute considerable interference in the TBA reaction. This was shown by chromatographic separation and spectrophotometric analyses of TBA pigments. A satisfactory application for milk uses trichloroacetic acid to remove fat and protein and ethanolic-TBA to increase the rate of color formation at 60C, a temperature at which lactose degradation is minimized. Results are presented showing quantitative recovery of oxidized milk from mixtures of oxidized and nonoxidized milk. Effect of exposing homogenized milk to direct sunlight for 20-min intervals is readily detected by the method. Relation between organoleptic and TBA analyses is indicated.