chapter  18
Antioxidant Mechanisms
Pages 22

I. Introduction ........................................................................................................................ 475 II. Inactivation of Free Radicals.............................................................................................. 476

A. Tocopherols ................................................................................................................ 479 B. Synthetic Phenolics..................................................................................................... 480 C. Ubiquinone ................................................................................................................. 483 D. Plant Phenolics ........................................................................................................... 484 E. Carotenoids ................................................................................................................. 484 F. Water-Soluble Free Radical Inactivators.................................................................... 485

III. Control of Lipid Oxidation Catalysts ................................................................................. 486 A. Control of Prooxidant Metals ..................................................................................... 486 B. Control of Singlet Oxygen ......................................................................................... 488 C. Control of Lipoxygenasses ......................................................................................... 488

IV. Inactivation of Oxidation Intermediates ............................................................................. 488 A. Superoxide Anion....................................................................................................... 488 B. Peroxides..................................................................................................................... 489 C. Photoactivated Sensitizers .......................................................................................... 490

V. Alterations in Lipid Oxidation Breakdown Products......................................................... 490 VI. Surface-Active Antioxidants and Physical Effects............................................................. 490 VII. Antioxidant Interactions ..................................................................................................... 491 References ..................................................................................................................................... 492

Krinsky [1] has defined biological antioxidants as ‘‘compounds that protect biological systems against the potentially harmful effects of processes or reactions that cause extensive oxidations.’’ While food lipids are derived from biological systems, the ultimate purpose of food antioxidants is different, since they are used to inhibit oxidative reactions that cause deterioration of quality (e.g., of flavor, color, nutrient composition, texture). With this goal in mind, food antioxidants can be defined as any compounds serving to inhibit oxidative processes that deteriorate the quality of food lipids. Antioxidant mechanisms that fit this definition include free radical scavenging, inactivation of peroxides and other reactive oxygen species, chelation of metals, and quenching of secondary lipid oxidation products that produce rancid odors.