Interpretation of the spectra of meat pigments. II.—Cured meats. The mechanism of colour fading

Spectral studies carried out indicate that the pigment of the cooked cured meats and that of the denatured nitric oxide haemoglobin is a low‐spin ferrous‐porphyrin co‐ordination complex. The spectra of the nitric oxide haemochrome prepared from haemin, derived from cured meat, and that of the acetone extract of the same cured meat give strong evidence that both co‐ordination positions of the iron ion in these compounds are occupied by nitric oxide and that globin is not associated with the molecule. Further evidence is presented by electron paramagnetic resonance studies, which show that the acetone extract of the cured meat pigment is diamagnetic. The pigment of the fresh cured meats and that of the nitric oxide haemoglobin are identical. They are low‐spin ferrous‐porphyrin co‐ordination complexes, but the one coordination position of the iron in these compounds is occupied by globin and the other by nitric oxide. A mechanism of the fading of the cured meat colour is presented, as well as theoretical considerations for the preparation of cured meats with stable colour.