Does color matter? This meaty issue has surprising applications. Photo courtesy: digiology

Does color matter? This meaty issue has surprising applications. Photo courtesy: digiology

11/28/2006

The Tint of the Turkey

By Eric Bland

Last week, the Thanksgiving turkey came out of the oven and received a place of honor in the middle of the table, likely surrounded by cranberry sauce, stuffing (inside or outside the turkey), mashed potatoes with gravy and yams.  Someone around the table stood up with a big carving knife, turned to you and asked the question:  white or dark?

Before you answered, you may have paused to consider the difference between white meat and dark meat.  Why exactly is white meat white and dark meat dark?  It has to do with the way a bird uses its muscles, and has led to a way to turn dark meat into white meat.  Dark meat-inducers in the wrong place can even reveal a heart attack.

The most obvious difference between white and dark meat (besides the color) is the taste.  White meat tends to be lean, bland, and consistent.  Dark meat has a richer, gamier and oilier taste and tends to have more fat.  Dieters avoid dark meat because of this, but chefs love it; dark meat is juicier and holds sauces and marinades better.  A majority of Americans prefer white meat over dark meat.  A few years ago McDonald’s even ensured that all Chicken McNuggets would be white meat.  

But back to the difference in color.  Since turkeys and chickens run everywhere but can only imperfectly fly, the energy needs for the different muscle groups are different.  Muscles need energy, and they get part of that energy from oxygen.  When a turkey (or human, for that matter) breathes in normally, red blood cells pick up the oxygen and transport it to the muscles and organs.  Red blood cells get their ruddy complexion from iron, which is locked up inside a molecule called hemoglobin.  Muscle cells contain a cousin of hemoglobin called myoglobin.  Since myoglobin contains iron as well, it gives frequently-used muscles a darker tint.  

While hemoglobin will give up oxygen relatively easily, myoglobin holds onto oxygen extremely tightly and will only release it when the muscle isn’t getting enough oxygen from the blood.  The more you work the muscle the more energy is required.  Myoglobin basically acts like a little backup battery for your muscles; when the oxygen supply from the blood runs out, myoglobin supplies extra.  And it’s even upgradeable; the more you exercise, the more myoglobin in your muscles.  Thus, turkey legs and thighs are darker than the less-used wings and breast muscles.  Additionally, this is a reason why an iron deficiency leads to fatigue—your blood can’t get enough oxygen to your muscles.  

Myoglobin in muscles is vital but in the blood stream it’s toxic.   Damaged muscles release myoglobin into the bloodstream, which destroys the kidneys in a condition called rhabdomyloysis.  Because heart attacks damage cardiac muscles, the resulting myoglobin in the blood can be used to detect a heart attack.  However, it’s an expensive test and is rarely used.

But what if no one in your family likes dark meat?  Don’t just throw the legs and thighs out; let the University of Georgia help you.  Last year researchers there put mashed dark meat into a centrifuge (a machine that spins very quickly in a circle) and presto, the myoglobin and fat are separated and removed and white meat exists where before there was only dark.

After you and yours stuffed yourselves and moved from the dinner table to couch to watch football, turning your own dark meat a slightly lighter tint from lack of use, don’t blame the turkey.  Blame the myoglobin.