ALPHA-TOCOPHEROL, GAMMA-TOCOPHEROL AND DELTA-TOCOPHEROL EFFECTS ON CHLOROPHYLL PHOTOSENSITIZED OXIDATION OF SOYBEAN OIL

The effects of 0, 1.0, 2.0 and 4.0 (x 10(-3) M) alpha-, gamma- or delta-tocopherol on chlorophyll b photosensitized oxidation of soybean oil in methylene chloride were studied by peroxide values and headspace oxygen. As concentrations of tocopherols increased, peroxide values decreased and headspace oxygen increased (P < 0.05). At 1.0 x 10(-3) M, alpha-tocopherol showed highest antioxidant effect, gamma-tocopherol second and then delta-tocopherol. alpha- and gamma-Tocopherols had similar effects and delta-tocopherol had lower effect at 2.0 x 10(-3) M (P < 0.05). However, the three tocopherols were not different (P > 0.05) at 4.0 x 10(-3) M. alpha-Tocopherol quenched singlet oxygen to reduce the photosensitized oxidation of oil. The quenching rate constants of alpha-tocopherol were 2.7 x 10(7)M-1sec-1 by peroxide value and 2.6 x 10(7) M-1sec-1 by headspace oxygen.