Meat+Poultry - September 2019 - 49

THE FIRST 24-HOURS
Chilling is simply not just heat removal. The
rate and extent of chilling impacts many
factors, including biochemical and structural
changes occurring in carcasses that determine
the ultimate product. Initially muscle is still
working to maintain its necessary biological
activities and energy pathways, so it breaks
down glycogen through postmortem glycolysis
for ATP production, but with a side effect of
the buildup of lactic acid as a byproduct. Lactic
acid causes the pH of the muscle to decrease
from 7.0 to 5.6 under normal conditions (too
little or too much lactic acid in the postmortem
muscle is what causes the conditions of dark
cutting/dark, firm, and dry or pale, soft, and
exudative, respectively). As long as there
are sufficient supplies of ATP present, the
muscles will be in a relaxed state. Once
ATP supplies diminish, rigor mortis begins
to develop causing the muscles to become
inextensible. Both postmortem glycolysis and
the rate of rigor mortis are greatly influenced
by temperature. Higher temperatures speed up
both processes, and lower temperatures slow
them down.

BEEF CHILLING

larger and heavier beef and pork carcasses.
"Hot boxes," the term used to describe the
initial chilling coolers, are taxed with having to
hold carcasses that require more room, which
results in little to no space for sufficient air
movement around them for adequate chilling.
These heavier carcasses simply contain more
heat than smaller carcasses and managing the
chilling processes to ensure that carcasses
are adequately chilled in a timely manner so
that fabrication/cutting can commence can be
difficult for some establishments.

Carcass
chilling
impacts
food safety,
minimizes
shrinkage
and
maximizes
shelf life of
the finished
products.

During the late 1950s and early 1960s, it was
determined that carcasses must be chilled
quickly before they could be exported to
Europe. Researchers discovered that there was
a toughness to the meat associated with this
change. The term coined for this phenomenon
was "cold shortening," which meant that the
muscles would undergo shortening at the
microscopic level due to the exposure to
cold temperatures before rigor mortis set in.
Scientists began exploring ways to prevent
this cold-induced toughening. Many different
strategies, such as the application of electrical
stimulation, alternative carcass suspension
methods and, of course, different ways to chill
carcasses were investigated.
For beef, the challenge was how to reduce
carcass temperatures rapidly enough to meet
export requirements without doing it so quickly
that cold shortening would be a problem.
One such approach was to simply delay
chilling. This allowed some of the postmortem
conditions to run their course, thereby
minimizing the effects of cold shortening,
before the carcasses were moved into colder
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