White Meat and Dark Meat: Why are they different?

June 30, 2008

If you’re a meat eater, it’s impossible not to have noticed that the chicken breast you’re eating looks different from the steak across the table. But why do different meats have different colors when they are all muscle tissue? Why is a chicken leg darker than the breast? How do these differences affect flavor?

There are two basic types of muscle fiber: white and red.

White Muscle Fiber

White muscle fiber is used for quick bursts of energy. For example, a chicken flapping its wings to fly away when you startle it is a use of white muscle fiber. Because a chicken’s wings are used only for short, quick bursts of energy, chicken breasts are almost all white muscle fiber. This fiber uses glycogen for energy, a compound stored in the tissue, and does not require oxygen to operate.

Red Muscle Fiber

Red muscle fiber is used for more constant, longer lasting activity. This energy comes mostly from fat cells and requires oxygen. Two proteins, myoglobin and cytochromes, are the key to metabolizing the fat with oxygen and they give red muscle fiber its dark color.

As you can imagine, grazing cows don’t often make sudden movements, so most of their muscle is red fiber. It is interesting, however, that while chicken breast is almost all white fiber, duck breast is mostly dark because it is used constantly during migration. Mixtures of white and red fibers are frequent, such as in chicken legs which are about half red and half white.

Flavor

When cooked, amino acids, sugars, fatty acids and other compounds react to form different flavors. Meats with mostly red fiber end up having more flavor because the tissue has a wider variety and greater abundance of compounds that break down and react to form flavors. More specifically, the fat in the tissue that is converted into energy and the membranes that contain the cytochromes contribute significantly to this increased flavor. White muscle meat generally has less flavor.

What does this mean for the cook? If you are looking for a meaty flavor, stick with well exercised red meats like beef, lamb, or duck. Or choose parts of the animal that contain are exercised more consistently, like the legs of poultry. If you want a more subtle flavor, go with the white meat of chicken or younger cuts of red meat like veal, which contains less red muscle fiber.

Posted in Food Science |