Why is red meat red? And why is white meat white? These are the two questions that many people ask themselves or search for an answer, even though they know that red meat is typical of mammals, such as ruminants (cattle, deer, sheep, goat), horse, and hog, and that white meat is common in fish and poultry (farm birds). The answer to these questions lies in the sarcoplasm, which is the cytoplasm of the cardiac and skeletal muscle fiber (myocyte).
Aside from myofibrils, the sarcoplasm contains a reddish brown protein called myoglobin, which is somewhat similar to the hemoglobin, the protein found in the blood erythrocytes. Myoglobin takes up oxygen from the blood and stores it in the sarcoplasm, so that it is available in the amount needed for energy production in the form of ATP, which is carried out by the cell mitochondria. A high amount of myoglobin and abundant mitochondria are characteristic of red and dark color muscles; hence the red meat of mammals and the dark-reddish brown meat of wild birds, such as wild partridge, quail, and mallard. The muscles of these wild fowl hold a high quantity of both myoglobin and mitochondria, while the white meat of fish and farm birds have only scarce amount of myoglobin.
Why is red meat red? Physiological reason
As aforementioned, the dark-red color is due to the preponderance of red muscle fibers, which have abundance of myoglobin and mitochondria. A substantial content of these two components enables these red fibers to maintain contraction over longer periods of time, during harsh physical exertions. There are other types of skeletal muscle, such as white meat, like the pectoral muscle in chicken, which contains a high proportion of white fibers; this is due to the fact that they have a scarce amount myoglobin and mitochondria. Adapted for shorter bursts of rapid contractile activity, these lighter-colored muscles exhaust more rapidly.
Finally, intermediate muscle fibers are structurally and functionally intermediate between red and white fibers. Most human muscles are made up of red and intermediate fibers. It is very important to point out that people that work out in a gym, or perform labor jobs that demand strenuous physical exertion, with a diet rich in animal proteins, will develop more red muscle fibers than intermediate. In the same way, it is important to note, that poultry or farm birds, which do not fly, nor run, and are fed on unnatural feed, have white fiber muscle, or meat. In contrast to poultry, wild fowl, which fly or run constantly and eat wild natural feed, have reddish or dark brown muscle fibers, even in their pectoral muscles.
Below, on the left, wild partridge meat, which is read, and, on the right, a farm chicken.
Below, the traditional beef steak (mammal meat).
