Sarcomere shortening of prerigor muscles and its influence on drip loss.

Detailed studies of muscle shortening post mortem at incubation temperatures between -2°C and +38°C revealed that the sarcomeres in unrestrained, excised red bovine muscle (M. sternomandibularis) shortened less than 10 % in the prerigor state between 6°C and 18°C. Below 6°C, sarcomeres contracted up to 70%. Between 20°C and 38°C sarcomere shortening of 40% was observed. In the red porcine M. cleidooccipitalis the minimum of shortening was measured at about 10°C, a higher degree of shortening-up to 50%-being obtained above and below this temperature. The drip loss of both muscle types increased linearly with increasing prerigor shortening. This latter relationship is discussed with regard to changes within the muscle post mortem. The influence of three events on water movement from the interfilamental space into the interfibrillar fluid and from there into the extracellular space is critically evaluated. These events are: (1) the prerigor contraction of sarcomeres depending on the temperature of storage, (2) the changes due to the falling pH post mortem and (3) the onset of rigor mortis, with its irreversible association of actin and myosin.