Prooxidative Activity of Myoglobin Species in Linoleic Acid Emulsions

Initiation of lipid peroxidation in oil-in-water linoleic acid emulsions catalyzed by metmyoglobin (MbFe(III)), metmyoglobin/oxymyoglobin (MbFe(III)/MbFe(II)O 2 ), ferrylmyoglobin (MbFe(IV) O), and perferrylmyoglobin ( • MbFe(IV) O) was investigated in the pH area of interest for meat and meat products (pH 5.5−6.5). MbFe(III), MbFe(IV), and MbFe(III)/MbFe(II)O 2 showed similar lipid hydroperoxide dependent catalytic efficiency in initiating lipid peroxidation. The presence of lipid hydroperoxides, in heme protein-initiated lipid peroxidation, was found to be the crucial factor rather than the redox state of heme proteins. In contrast, • MbFe(IV) O, formed in situ by reaction of MbFe(III) with H 2 O 2, was an ineffective catalyst, as it undergoes intramolecular electron transfer resulting in heme globin cross-linkage to yield a green iron(III) heme pigment rather than reacting with the lipids.