STABILITY OF HEME PIGMENTS IN MODEL SYSTEMS AND COOKED MEAT

The stability of sheep haemoglobin and myoglobin in aqueous solution a t 80, 100 and 121-degrees-C for 1 h was measured by subjecting portion s of the heated solutions to electrospray mass spectrometry (ESMS). ES MS dissociates haem proteins into the globin chains and the haem moiet y and, with haemoglobin, degradation of the alpha-(15047.5 Da) and bet a-(16073.3 Da) chains was observed at all heating temperatures. Under the same conditions, sheep myoglobin dissociated into the globin (1692 3.2 Da) and haem parts but the globin was stable and few degradation p roducts were observed in the ESMS trace (mass range 4-20 kDa) even aft er 1 h at 121-degrees-C There did seem to be limited breakdown of the globin due to loss of 170 Da. From the amino acid sequence, it is post ulated that this is due to loss of GLY-LEU from the N-terminus. Method s for extracting myoglobin from raw and cooked meat were then investig ated. Water was adequate for myoglobin extraction from raw meat but ur ea solution was required for adequate extraction of cooked meat sample s. Sheep meat was heated at 80, 100 and 121-degrees-C in sealed cans, extracted and the mass profile in the range 4-20 kDa measured. Myoglob in was the major peak when samples were heated for 10, 20, 30 and 40 m in. After that time, other peaks appeared although the myoglobin globi n chain was still apparent. The results are discussed in relation to u sing myoglobin as a marker for meat speciation.