Chemical and Functional Properties of Food Saccharides

The ultimate pH of meat after rigor mortis may range between 7.0 and 4.8.
Usually, pH of meat of standard quality ranges between 5.3 and 5.8 for pork, veal,
beef, and lamb, and between 5.8 and 6.0 for poultry. 5
The rate of postmortem glycolysis in skeletal muscles depends on the temperature
at which the carcass is cooled. Also, composition of muscle fiber type; species,
breed, and sex of animals; resistance to stress; and processing of the carcass after
slaughter, as, for instance, electrical stimulation, storage temperature, prerigor cutting
and curing, influence glycolysis.
The rate of glycolysis is higher in white muscle fibers than in the red, because
the activity of muscle ATPases in white muscle fibers is higher than it is in red
muscle fibers.
Muscle stimulation associated with the activity of the animal prior to its slaughter,
electrical stunning at the time of slaughter, and electrical stimulation of freshly
slaughtered carcass result in intensified release of calcium ions from the sarcoplasmic
reticulum and mitochondria and increase the rate of postmortem glycolysis.
The rate of postmortem glycolysis in anatomically the same muscles but from
another specimen can be entirely different. It is important in determining the ultimate
properties and quality of meat (Figure 16.3).
A normal pH decline pattern in porcine muscle is represented by a gradual
decrease from approximately pH 7.4 in living muscle to a pH of about 5.6 to 5.7
within 6 to 8 h postmortem, and then to ultimate pH (reached at approximately 24
h postmortem) in range of 5.3 to 5.7. In some animals, the pH drops only slightly
during the first hour after slaughter and remains stable at a relatively high level,
giving an ultimate pH in the range of 6.5 to 6.8. In other animals, muscle pH drops
rapidly to around 5.4 to 5.5 during the first hour after exsanguination. Meat from
these animals ultimately develops a pH in the range of 5.3 to 5.6.
pH
© 2004 by CRC Press LLC
7.0
6.5
6.0
5.5
5.0
1 2 3 4 5 6 24
Hours Post-Mortem
Meat Quality
Dark, firm, and dry
Normal
Pale, soft, and exudative
FIGURE 16.3 Effect of postmortem pH decline on the meat quality. (Modified from Briskey,
E.J. et al., J. Agric. Food Chem., 14, 201, 1966.)