Studies on Oxidative Rancidity of Fat and Oil (II)

Thiobarbituric Acid-reaction of Autoxidized Methyl Linolenate and Its products

Abstract

The oxidation of methyl linolenate in diffused daylight, and under UV ray γ ray was studied by pursuing changes of its thiobarbituric acid (TBA) value, peroxide value, quantity of conjugated diene, carbonyl value, and rate of weight increase. As a result, it was found that the tendency of changes in TBA value and cardonyi value were similar, and that UV ray did not only accelerate to produce the first oxidative product[s]of methyl linolenate, but did more intensely to decompose this product[s], which influenced TBA value and carbonyl value after UV treatment.
Three pigments were always identified from the reaction products of oxidized methyl linolenate and TBA by chromatography without regard to the methods and various stages of oxidation. The pigment 1, λ max. 454mμ, seemed to be similar to n-vaieraldehyde-TBA condensation product from the viewpoint of chromatographic behaviours and spectro-photometric character, which was presumed as one of substances disturbing TBA value. The pigment 2, λmax. 510mμ, was found to be very small in quantity amoag the reaction mixtures. The pigment 3, λmax. 532mμ, was identified as the object of TBA value and a malonaldehyde-TBA condensation product.