Conversion Of Muscle To Meat

When an animal is stunned and exsanguinated, oxygen supply to the muscle ceases and a series of biochemical changes commences. The end result depends on the condition of the animal and preslaughter handling. The main metabolic events are a depletion of the ATP energy store and a degradation of the glycogen, which is converted an-aerobically to lactic acid. Accumulation of lactic acid results in a decline of pH from near 7.0 to the range of 5.5 to 5.9; this is a postmortem condition easily monitored to establish rate and status of changes in the muscle as it is converted to meat. Rigor mortis also occurs as the muscle is converted from a soft, pliable, and extensible condition to one of rigidity. This is explained by a locking together of the myosin to actin filaments as ATP depletes. The time for rigor mortis differs with species, with beef and lamb being longer than pork and poultry. Some shortening of muscle occurs during the onset of rigor mortis. There are also two other shortening conditions of interest to meat science. Cold shortening results when muscle is exposed to a low temperature prior to ordinary development of rigor mortis, and it may result in considerable toughening. If meat is frozen prior to the onset of rigor mortis, it may then shorten greatly when thawed. This is known as thaw rigor and results in severe toughening. The postmortem changes also influence color and water-holding capacity of the resulting meat. This is quite important in pork, where a rapid pH decline results in so-called pale, soft, and exudative (PSE) meat. In beef, a dark, firm, and dry (DFD) condition may result if the pH remains high. These undesirable conditions are due largely to the genetic predisposition of the animal. However, proper handling both pre-and postmortem is important. Preslaughter stress to the animal can greatly influence postmortem events. Likewise, postmortem handling, such as proper temperature control during the chilling process, influences the final outcome. Other procedures, such as electrical stimulation, employed during postmortem time can be used to control tenderness and quality of meat.

The Mediterranean Diet Meltdown

The Mediterranean Diet Meltdown

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