Metmyoglobin and inorganic metals as pro-oxidants in raw and cooked muscle systems.

The pro-oxidant activities of metmyoglobin (Mb) and metal ions on the induction of lipid oxidation in raw and heated water-washed muscle systems from fish, turkey, chicken, pork, beef and lamb and during storage of these systems at 4°C, were investigated. Lipid oxidation was invariably faster in heated than in raw systems. In raw Mb-catalyzed systems, oxidation was slow over a 5-day period, except in fish, where significant (P < 0·05) increases in TBA values occurred; in contrast, significant (P < 0·05) increases in TBA values occurred in cooked fish, turkey, chicken and pork after 3 days of storage. Cooked beef and lamb, however, showed significant lipid oxidation only after 5 days of storage. Fe(2+) was found to be highly catalytic in cooked muscle. Cu(2+) and Co(2+) were less effective catalysts than Fe(2+); the overall pro-oxidant activity was in the order Fe(2+) > Cu(2+) > Co(2+) > Mb, and the susceptibility to lipid oxidation of the muscle systems was in the order: fish > turkey > chicken > pork > beef > lamb, probably reflecting the degree of unsaturation of the constituent triglyceride fractions.