1. What factors affect the color of meat
and poultry?
Myoglobin
, a protein, is responsible for the majority
of the red color. Myoglobin doesn’t circulate in the
blood but is fixed in the tissue cells and is purplish
in color. When it is mixed with oxygen, it becomes
oxymyoglobin and produces a bright red color. The
remaining color comes from the hemoglobin which
occurs mainly in the circulating blood, but a small
amount can be found in the tissues after slaughter.
Color is also influenced by the age of the animal,
the species, sex, diet, and even the exercise it gets.
The meat from older animals will be darker in color
because the myoglobin level increases with age.
Exercised muscles are always darker in color, which
means the same animal can have variations of color
in its muscles.
In addition, the color of meat and poultry can change
as it is being stored at retail and in the home (see
explanation in question 5). When safely stored in the
refrigerator or freezer, color changes are normal for
fresh meat and poultry.
http://www.fsis.usda.gov/wps/wcm/connect/e8dad81f-f7fc-4574-893e-bae20cf8b215/Color_of_Meat_and_Poultry.pdf?MOD=AJPERES