Temperature

For optimum meat quality, meat should be held at 59 to 61 degrees Fahrenheit (15 to 16 degrees Celsius) during the onset of rigor mortis. Temperatures which are too low can result in unfavorable conditions such as thaw rigor and cold shortening. Temperatures which are too high can results in heat rigor.

Thaw Rigor and Cold Shortening

When meat is frozen before the onset of rigor mortis, a more severe form of rigor mortis will set in upon thawing the meat. This is called thaw rigor. When this occurs, severe muscle contractions will cause the length of the muscle to shrink 60 to 80 percent. The resulting meat is very tough and lacks juiciness.

When meat is not frozen but is stored between 32 and 59 degrees Fahrenheit (0 and 15 degrees Celsius), cold shortening develops, which is similar to but less severe than thaw rigor. Muscles which are not attached to the skeleton are the most severely affected but there will also be some undesirable effects in those, which are attached to the skeleton. Beef and lamb are particularly susceptible to this condition, but it occurs in other meats as well. Carcasses with lower fat content lose their heat more quickly and will be more severely affected than carcasses with higher fat content. Electrical stimulation can be used to prevent cold shortening especially in beef and lamb.

Heat Rigor

Muscle which is held at temperatures above the optimum temperature (above 59 to 61 degrees Fahrenheit) will have severe shortening due to early onset of rigor mortis. This condition results in tough, less juicy meat.