Protein antioxidants for the stabilization of lipid foods: current and potential applications - Oxidation in Foods and Beverages and Antioxidant Applications - page 250

Fig. 11.1 Tocopherol and tocotrienol structures.
decomposition of lipid hydroperoxides (Decker and McClements, 2001; Frankel,
1998; McClements and Decker, 2000; Min and Boff, 2002; Nawar, 1996). Due
to the fact that all food products contain trace amounts of metals, and that it is
not practical or feasible to remove metals from food ingredients, metal-catalyzed
decomposition of hydroperoxides is an important reaction in the oxidation of
food lipids. Two metal-hydroperoxide reactions, which follow classical Fenton
chemistry, are typically observed.
The application of metal inactivators, or chelators, to food lipids is often an
effective strategy for inhibiting lipid oxidation. In the presence of metals,
chelating compounds can form chelates, or complexes resulting from the com-
bination of a metal ion and a multidentate ligand such that the ligand forms two
or more bonds with the metal, resulting in a ring structure that includes the metal
ion (Miller, 1996). By complexing with transition metals in such a manner, the
Fenton-mediated decomposition of lipid hydroperoxides is effectively disrupted.
Common inactivating chelating compounds include citric acid, phosphoric acid,
ethylenediaminetetraacetic acid (EDTA), and 8-hydroxy-quinoline (Frankel,
1998). Other compounds are capable of strongly binding metals without
rendering them redox inactive. Such compounds can alter the physical location
of metal-catalyzed reactions, thus inhibiting lipid oxidation by preferentially
partitioning metals to regions of low-lipid concentration.
Substances that safely destroy peroxides inhibit oxidation reactions by
converting lipid hydroperoxides into non-reactive species. The inactivation of