Aspects of myoglobin and hemoglobin-mediated lipid oxidation in muscle foods and its inhibition

Abstract: Hemoglobin (Hb) and myoglobin (Mb) provide red coloration to raw muscle tissue and can promote lipid oxidation during storage. Reasons that Hb is more pro-oxidative than Mb are presented which includes lower heme affinity of Hb. Plasma induced modification of biomolecules (PLIMB) with tandem mass spectrometry is presented as a rapid, benchtop technique to assess solvent accessible sites of proteins in relation to heme affinity of fish and bovine metHb. Caffeic acid and epigallocatechin gallate are shown to be reactive with Hb to form metHb and quinone; the quinone covalently binds to specific sulfhydryls of certain Hbs, generating the reduced phenol. Crystal structures of bound phenol to Hb are presented to highlight distances required for electron transfer from the bound phenol to the heme iron. The phenol bound to Hb is found to be both pro-oxidative and antioxidative in model systems. Carnosol present in commercial rosemary extracts is found to covalently bind to an avian Hb. Involvement of polyphenols in the peroxidase activity of Mb and Hb is also presented as a possible antioxidant mechanism. Phospholipase A2 is shown to inhibit Hb-mediated lipid oxidation in a washed muscle model system and to inhibit lipid oxidation in pork sausage when in combination with rosemary extract. Possible mechanisms of antioxidant action include modifying phospholipids so that Hb interacts less with the lipid phase and conversion of the liberated free fatty acid hydroperoxides to hydroxides by methionine residues of myofibrillar proteins or other reductants.