for the following reasons:
a) to kill bacteria and make the meat safe to eat
b) to make the meat more digestible (denatured proteins are more easily digested than folded
c) to improve flavour
d) to reduce toughness (however, cooking may also increase toughness, as explained below)
What occurs on cooking?
As meat is heated, the muscle proteins start to denature. This starts at a temperature of approximately
40 °C, when the highly heat sensitive muscle proteins the myosins start to denature. This can be
visualised by the apparent loss of translucency - light can no longer pass through the gaps previously
present between the individual highly-folded proteins, and the meat loses some transparency. This
initial denaturation is also associated with an increased in juiciness of the meat - some liquid is
liberated as the proteins unwind. As temperature increase, the other proteins present will also start to
denature and coagulate. At around 60 °C, one of the last proteins denatures – this is the myoglobin,
and its denaturation has a much more important affect on the colour of the meat than the texture. The
myoglobin denatures to form a compound called hemischrome that is more a brown-gray colour (since
is similar t the colour change on brining meat).
So at the temperature where the meat changes colour from red to brown is to some extent associated
with the temperature at which the protein network is the most “juicy”, and this can be used as an
indicator for the doneness of meat – meat removed from the heat just after the meat goes brown (ie
when it is at a temperature of about 65°C) will be tender and juicy.
With continued heat, the networks of meat proteins will start to strengthen, and water will be squeezed
out of this network, which will then evaporate, and then meat will shrink. These strong protein
networks makes the resulting meat difficult to chew, and the meat will appear much dryer. So the
longer the meat is heated, the tougher and drier it becomes. Hence a well done steak is much drier