EFFECT OF SALT ON MYOGLOBIN DERIVATIVES IN THE SARCOPLASMIC EXTRACT FROM PRE-RIGOR AND POST-RIGOR BEEF IN THE PRESENCE OR ABSENCE OF MITOCHONDRIA AND MICROSOMES

The effect of salt and pH on the colour stability (oxymyoglobin) in the sarcoplasmic extract (SPE) prepared from pre- and post-rigor beef muscle was studied in the presence or absence of mitochondria and microsomes during 96 h at 4°C. The sarcoplasmic extract from the post-rigor meat (pH 5·4) or from the pre-rigor meat adjusted to pH 5·4 contained more oxymyoglobin (MbO2) than the pre- or post-rigor SPE maintained at pH 7·4. The presence or absence of mitochondria and microsomes in the SPE at pH 5·4 had little effect on the percentage of MbO2. At pH 7·4, however, the percentage of MbO2 decreased in the SPE in the presence of mitochondria, whereas the percentage of MetMb was lower in the presence of microsomes. The relative proportion of MbO2 decreased and that of metmyoglobin (MetMb) increased with increasing salt concentration at low pH (more so in the absence of subcellular organelles) and with storage period in the SPE from both pre- and post-rigor meat. However, at pH 7·4, high levels of salt (2-4%) helped to maintain a high percentage of MbO2 in SPE in the absence of subcellular organelles, especially the mitochondria. The first-order interactions of pH value × subcellular organelles (P < 0·01) and pH value × salt concentration (P < 0·01) accounted for about 55% of the total variation in the percentage of MbO2 in the SPE. It is suggested that depressing microbial growth may be the operative mechanism by which added salt stabilizes the colour in pre-rigor minced meat rather than by enzymic effects of subcellular organelles. © 1990.