INHIBITORY EFFECTS OF TOCOPHEROLS AND ?-CAROTENE ON SINGLET OXYGEN-INITIATE D PHOTOOXIDATION OF METHYL LINOLEATE AND SOYBEAN OIL

Abstract

Methyl linoleate was photooxidized in the presence of chlorophyll at 37.degree. C and the change in the isomeric composition of monohydroperoxides (MHP) produced was measured. The result of increasing the proportions of the 9- and 13-isomers with the elapse of time shows that autocatalytic oxidation occurs with the accumulation of MHP produced by singlet oxygen (1O2). .delta.-Tocopherol had the most inhibitory effect on the production of MHP among .alpha.-, .gamma.- and .delta.-tocopherols, by suppressing autocatalytic oxidation and by quenching 1O2. .alpha.-Tocopherol scarcely inhibited the production of MHP, because .alpha.-tocopherol disappeared rapidly during photooxidation. .beta.-Carotene retarded the photoooxidation of methyl linoleate efficiently. The inhibitory effect of .beta.-carotene was elongated in the presence of .delta.-tocopherol. .beta.-Carotene efficiently inhibited the deterioration of soybean oil which was exposed to photoirradiation in the presence of tocopherols.