On Food and Cooking

The appearance of meat changes in two
different ways during cooking. Initially it’s
somewhat translucent because its cells are
filled with a relatively loose meshwork of
proteins suspended in water. When heated to
about 120ºF/50ºC, it develops a white opacity
as heat-sensitive myosin denatures and
coagulates into clumps large enough to scatter
light. This change causes red meat color to
lighten from red to pink, long before the red
pigments themselves are affected. Then,
around 140ºF/60ºC, red myoglobin begins to
denature into a tan-colored version called
hemichrome. As this change proceeds, meat
color shifts from pink to brown-gray.
The denaturation of myoglobin parallels
the denaturation of fiber proteins, and this
makes it possible to judge the doneness of
fresh meat by color. Little-cooked meat and
its juices are red, moderately cooked meat and
its juices are pink, thoroughly cooked meat is
brown-gray and its juices clear. (Intact red