LPT 321: Meat Science (1+1)

POSTMORTEM GLYCOLYSIS AND pH DECLINE

• In the absence of oxygen, anaerobic glycolysis leads to the formation of lactic acid from the glycogen reserves:

• The accumulation of lactic acid lowers down the muscle pH, which is an important postmortem change during the conversion of muscle to meat.
•  The rate and extent of pH decline are variable, being influenced by the species of food animal, various preslaughter factors, environmental temperature, etc.
• In most species, a gradual decline continues from approximately pH 7 in the living muscle during first few hours (5-6 hours) and then there is a little drop in the next 15-20 hours, giving an ultimate pH in the range of 5.5 – 5.7.
• The rate of pH decline is enhanced at high environmental temperature. A low ultimate pH is desired to have a check on the proliferating microorganisms during storage.
• A sharp decline in postmortem pH even before the dissipation of body heat through carcass chilling may cause denaturation of muscle proteins. So, the muscles depict pale, soft and exudative (PSE) condition.
•  Contrary to this, muscles which maintain a consistently high pH during postmortem conversion to meat due to depletion of glycogen prior to slaughter depicts a dark, firm and dry (DFD) condition. Both the conditions are undesirable.