Biochemical changes in beef muscle post mortem and the effect of rapid cooling in ice

The biochemical changes resulting from glycolysis and ATP (adenosine‐5′‐triphosphate) degradation were investigated in either the M. semimembranosus or the M. semitendinosus of 7 beef carcasses, during the first 24 hours post mortem. The effects of ice‐cooling were compared with normal air‐cooling at the slaughterhouse. Lactic acid production and pH fall in the muscle indicated a high turn‐over of ATP in the first hour post mortem. ATP was maintained at a high level, chiefly by the glycolytic pathway, during this first hour, and then declined as the pH continued to fall. The occurrence and turn‐over of the various degradation products of ATP was recorded. A loss of water holding capacity and a loss of protein solubility occurred continuously during the 24 hours; the relation between these changes and the observed fall in pH and in ATP levels is discussed. Ice‐cooling increased the rate of temperature fall, at 4 cm depth in the muscle, by a factor of 1.5. This significantly retarded glycolysis and ATP breakdown, and reduced denaturation of protein and loss of water retention. IMP (inosine‐5′‐monophosphate) could be retained at higher levels in the icecooled muscles.