Biochemical processes and structural changes that occur in muscle during the first 24 h postmortem play a great role in the ultimate
quality and palatability of meat and are influenced by the chilling processes that carcasses are subjected to after slaughter. For
beef and lamb, employing chilling parameters that minimize cold shortening is of greatest importance and can be best addressed by
ensuring that muscle temperatures are not below 10 C before pH reaches 6.2. For pork, because of the impact of high muscle temperatures
and low pH on the development of pale, soft, and exudative (PSE) pork, a more rapid chilling process is needed to reduce
PSE with the recommended internal muscle temperature of 10 C at 12 h and 2–4 C at 24 h. Spray chilling, a system whereby chilled
water is applied to carcasses during the early part of postmortem cooling, is used to control carcass shrinkage and to improve chilling
rates through evaporative cooling. Delayed chilling can be used to reduce or prevent the negative effects of cold shortening; however,
production constraints in high-volume facilities and food safety concerns make this method less useful in commercial settings.
Electrical stimulation and alternative carcass suspension programs offer processors the opportunity to negate most or all of the
effects of cold shortening while still using traditional chilling systems. Rapid or blast chilling can be an effective method to reduce
the incidence of PSE in pork but extreme chilling systems may cause quality problems because of the differential between the cold
temperatures on the outside of the carcass compared to the warm muscle temperatures within the carcass (i.e., muscles that are darker
in color externally and lighter in color internally).