Post mortem reactions

Oxygen supply to the muscles is interrupted at slaughter by circulatory collapse. The metabolism shifts from aerobic to anaerobic operation.

Lactic acid then builds up in muscle tissue. It becomes more concentrated as metabolic processes continue, but there is no circulation to transport the lactic acid to the liver (where in the live animal it is resynthesized into glucose or glycogen).

Rigor mortis, or stiffness, occurs when the adenosine triphosphate (ATP) level is low and molecules combine in the muscle. After a variable period of time, rigor mortis reduces as the muscle softens.
pH after slaughter indicates if meat quality problems will develop. Photo: Ingemar Hansson