Text Box: 9:10 AM Text Box: Microbiology Text Box: The quenching mechanisms and kinetics of α-, β-, γ-, and δ-tocopherol in chlorophyll Text Box: Robert E. King and Dr. Min Text Box: Lipid oxidation is a serious concern for the food industry, due to the production of off-flavors and odors, discoloration, and the formation of toxic compounds. Chlorophyll is a natural photosensitizer. When exposed to light chlorophyll becomes excited and leads to the formation of singlet oxygen, which readily oxidizes fatty acids. Lipid oxidation can be slowed or prevented by antioxidants. Tocopherols (α, β, γ, and δ), commonly known as Vitamin E, have been showed to have antioxidant activity. This study examines the antioxidant mechanisms and kinetics of α-, β-, γ-, and δ-tocopherol in chlorophyll (4ppm) photosensitized oxidation of lard (0.03, 0.07, 0.11, and 0.3M). Lard oxidation was analyzed using headspace oxygen depletion and peroxide value. All tocopherol isomers were found to prevent lard oxidation via singlet oxygen quenching. Quenching rates determined from headspace oxygen depletion were 2.78 x 107, 2.21 x 107, 1.71 x 107, and 1.16 x 107M-1s-1 for β-, δ-, α-, and γ-tocopherol, respectively. Quenching rates determined from peroxide value analysis were 2.73 x 107, 1.39 x 107, 9.13 x 106, and 6.99 x 106M-1s-1 for γ-, α-, β-, and δ-tocopherol respectively. Peroxide value measures the hydroperoxide concentration within a sample. Hydroperoxides decompose during the oxidation process, making the analysis of quenching rates by this method less accurate than headspace oxygen depletion. The high quenching rates, as determined by headspace oxygen, of α, β, γ, and δ-tocopherol indicate that tocopherol isomers are effective singlet oxygen quenchers.