pH Dependence of the progression in NMR T(2) relaxation times in post-mortem muscle

Continuous NMR T(2) relaxation measurements were carried out on seven rabbit longissimus muscle samples in the period from 25 min to 28 h post-mortem at 200 MHz for (1)H. To display differences in post-mortem pH progress and extent of changes in water characteristics during conversion of muscle to meat, three of the seven animals were pre-slaughter injected with adrenaline (0.5 mg/kg live weight 4 h before sacrifice) to differentiate muscle glycogen stores at the time of slaughter. Distributed analysis of T(2) data displayed clear differences in the characteristics of the various transverse relaxation components dependent on progress in pH, as did the water-holding capacity of samples 24 h post-mortem. This reveals a pronounced effect of the progressive change in pH on the subsequent development in physical/chemical states of water during the conversion of muscle to meat. Finally, the relaxation characteristics are discussed in relation to supposed post-mortem processes of protein denaturation.