Studies on the structure and oxidation properties of extracted cooked cured meat pigment by four spectra

The structure and oxidation properties of cooked cured meat pigment (CCMP) were investigated by comparing the change in spectra of CCMP before and after oxidisation. CCMP was extracted using petroleum ether/acetone/ethyl acetate step by step from precooked cured beef. The extracted sample was oxidised by being exposed to air with normal lighting or adding 1.5 ppm H2O2, respectively. The structure of CCMP was identified as a pentacoordinate mononitrosylheme complex by electron paramagnetic resonance (EPR), HPLC/ESI-HR-MS, Raman and FT–IR spectra. The changed EPR spectra of CCMP in acetone oxidised under different conditions suggested a new proposal that the NO− group might not detach itself from iron porphyrin during oxidation in air with normal lighting, but changed in conjugated structure, and the structure tended to axial symmetry by analysis of the changes in g factor. This hypothesis was further supported by the results of the HPLC/ESI-HR-MS and Raman spectrum.