Sunday, December 15, 2002

How Do Chicken And Turkey Have Dark And White Meat?

Ever wonder why turkey legs at Thanksgiving have dark meat, while the breast meat is white? The simple answer is because dark meat has more blood vessels giving food and oxygen to those areas than white meat does. But there is much more to the story. Both white and dark meat are skeletal muscles--the kind of muscles that help you move. Muscles contract or shorten, and relax or get longer in order to help you move. The meats are different kinds of skeletal muscles, leading to their different colors. There are three main groups of skeletal muscles: fast twitch glycolytic (GLY-CO-LIT-IC), fast twitch oxidative (OX-A-DATE-IVE) and slow twitch.

What do these words really mean? Well, the muscle groups are named for how they work. The fast twitch glycolytic muscles are powerful muscles that contract or work quickly, but they tire out quickly too. Sprinters who run short distances have trained their legs to use many of these quick working muscles. Muscles that tire out quickly would not be much use to marathon runners who need lots of energy for longperiods of time. Marathon runners have more of the fast twitch oxidative muscles. These muscles also contract or work quickly, but tire out slowly. The reason they do not tire out as quickly as the fast twitch glycolytic muscles is that they have large numbers of factories producing energy especially for them. These energy factories are called mitochondria (MI-TO-CON-DRI-A) and they make energy for cells.

So we have muscles that contract quickly, but tire quickly and muscles that do not tire quickly but use up a lot of energy. What do we do when we need a muscle to contract or work all the time without using up all of our energy? We do not want to be walking around as if we just ran a marathon all the time! Imagine how tired we would be! This is why we have the slow twitch muscles. The slow twitch muscles are like the ones in our back. They are always contracted so we can sit up straight in our chairs. These muscles contain lots of blood vessels so that they can always get food and do not have to produce lots of their own energy with the help of mitochondria. Our body needs all three types of muscles to work properly.

But what does this have to do with chicken and turkey? What type of muscles do you think make up light and dark meat? Let's think about here the dark meat is on a bird. It is found in the thighs and drumsticks. Chickens and turkeys are always on their feet and they do not need to move quickly. Dark meat is therefore a slow twitch muscle. What about white meat? Birds fly rather then walk to get away from something. So it would make sense that they would have fast twitch muscles to help them fly. That is why you find white meat in the breast of a bird. Although chickens cannot fly like turkeys can, they are relatives of birds that can fly and that is why they still have white meat or fast twitch muscle that move their wings.

Little Lion Experiment:

Can you identify where all the different types of muscles in your body are found? Run a sprint down your block and see which muscles you use. Run a around your block a couple of times and try to figure out which muscles you use. Those are your fast twitch muscles. Think about what muscles would be your slow twitch muscles.

Next time your mom or dad has a whole chicken or turkey for dinner ask them if you can identify the different types of muscles while they cut it up. Let your parents handle the knife to cut up the poultry and always wash your hands after handling raw poultry.