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Early post mortem events

Early post mortem events. Buenos Aires Sept 2008. Outline. Consequences of circulatory failure. Muscle metabolism post slaughter. Effect on pH. Biochemistry of rigor mortis. Circulatory failure. Muscle continues using energy (ATP). Ultimate pH (pHu) 5.5 stops metabolism.

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Early post mortem events

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  1. Early post mortem events Buenos Aires Sept 2008

  2. Outline • Consequences of circulatory failure. • Muscle metabolism post slaughter. • Effect on pH. • Biochemistry of rigor mortis.

  3. Circulatory failure Muscle continues using energy (ATP) Ultimate pH (pHu) 5.5 stops metabolism Localised oxygen consumed (ie in blood) Rigor mortis pH declines due to lactic acid build up Aerobic metabolism stops Glycogen catabolised as fuel producing lactic acid ATP conc. falls stimulating anaerobic metabolism

  4. Muscle Metabolism • Two sources of energy (ATP) • Creatine Phosphate • glucose

  5. Creatine Phosphate • Short term energy supply (intense exercise). • ATP drops when Creatine Phosphate used up.

  6. ATP breaks actin/myosin linkages • enables muscles to relax again. - no ATP… rigor mortis!

  7. Glycolysis Aerobic Anaerobic Glucose Glucose ADP ADP Glycolysis Glycolysis ATP ATP Heat Some ATP Pyruvate Pyruvate Lactic acid Mitochondrial Wall Heat CO2 H2O ATP O2 TCA

  8. Changes in metabolite conc. post mortem

  9. pH decline • To rapid – heat shortening, or PSE (pale soft exudative meat). • To slow – cold shortening. • pHu (5.5) not reached – dark cutting meat (DFD meat).

  10. Factors affecting rate of pH decline • Muscle type (ie red/white) • Species (horse>pig>cow) • Temperature • Stimulation

  11. Rigor Mortis: Definition • Biochemical – ATP insufficient to break actin/myosin linkages. • Chemical – post mortem muscle pH is lower than 6.0 • Practical – muscle has “set”. Stiff to the touch.

  12. Rigor: biochemical scenario Slaughter Onset of rigor CP depleted Actin/myosin links increase Glycogen Lactate ATP conc. drops pH Ca2+ leaks ATP breaks links Actin/myosin links (contraction)

  13. Conclusions • Circulatory failure • Post Mortem muscle metabolism • Glycolysis • Creatine Phosphate • Factors affecting pH decline • Species • Muscle type • Temperature • Biochemistry of Rigor Mortis

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