During normal conditioning procedures, as the muscle goes into rigor there is shortening, which depends on the temperature of the muscle, being greatest at high and low temperatures in unrestrained muscle, and differs with species. Early classical studies (26) showed that the minimum shortening for beef occurred at about 15°C (Fig. 4), and other studies showed that the greater the amount of shortening, the greater the toughening of the cooked meat (27) (Fig. 5). Increases in shortening at rigor temperatures above 15°C are as expected, as such contractures would increase with temperature in a normal way. Increases in shortening with temperature falls below 15° to 0°C are unexpected and are likely to arise from a combination of reduced calcium binding by cell organelles with the fall in temperature, causing an increase in intracellular calcium. The increased contracture by the muscle through increased calcium levels is more than offset by the concomitant falloff in muscle responses at the lowered temperature. A more quantitative analysis of the effect of
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