A "Cold Shortening" Effect in Avian Muscle

SUMMARY— Experiments were conducted to determine the effect of post-mortem temperatures between 0 and 20°C on the degree of shortening in isolated pectoralis major muscles of chickens and turkeys. A "cold shortening" effect in these muscles is described and compared to post-mortem pH, average sarcomere length of isolated myofibrils, and relative solubility of myofibrillar and sarcoplasmic proteins.
The degree of muscle shortening at each temperature after various periods post-mortem indicated that shortening was essentially complete after 3 hr in chickens and 5 hr in turkeys. Shortening in muscles stored at 0°C was significantly greater (P < .01) than in the 12–18°C temperature range. Shortening was greatest in muscles stored at 20°C. The degree of gross shortening observed was directly related to the average sarcomere length of isolated myofibrils. Post-mortem decline in pH was not significantly correlated (P > .05) with shortening. Extractability of myofibrillar and sarcoplasmic proteins after 5 hr at either 0 or 16°C was determined and found to be unrelated to the degree of post-mortem shortening.