Teach science with your Thanksgiving left-overs
The remains of your holiday bird can be used to not only make good food, but also teach science.
This is an article in a series focusing on science activities about the natural world that anyone can conduct with children. This can be done in numerous settings including within a family, at day-care, as part of school activities, a 4-H club or with any group working with young children.
After having a wonderful dinner with family and friends, there is a science opportunity waiting in your refrigerator, and there is good food to be had in the process. Michigan State University Extension recommends asking lots of questions.
Before the big bird is baked, you will usually notice a bag with strange looking parts, called giblets, tucked inside the body cavity. What do you do with those things? Usually giblets include the neck, heart, gizzard and liver of the turkey. What did the bird use them for when they were still alive? What can we learn from them?
- Neck – The neck is used to hold up the head. The reason it is usually removed is to make it easier to pack and fit in your fridge. The neck also contains the spinal cord, which transports messages from the brain to the body. After it has cooked, making stock (see below), you can try to move it around and look at the parts which help hold it together versus those that send messages.
- Heart – Most are familiar with the heart, and that it is not actually heart-shaped. Birds have four-chambered hearts, just like mammals. If you pull the heart out and slice it down the middle, try to identify the four chambers. Does it seem strange that something so small can pump blood throughout the entire turkey?
- Gizzard – Since turkeys don’t have teeth, they swallow grit and grind up their food in a strong muscle called a gizzard to break down their food. Potterville, Michigan, has a Gizzard Fest every year.
- Liver – Livers do lots of jobs for us (and for turkeys too). Livers remove “bad stuff” from our bodies. Livers make bile that helps us digest fat. Livers store vitamins and minerals.
When everyone is done eating turkey, and you have most of the meat removed from the carcass for leftovers, don’t throw the bones away. There is more science and good food to be had.
Stock is a flavorful liquid that is the basis for many foods, especially soup. To make stock, first boil the carcass (all the leftover skin, bones, giblets and uneaten parts) with some carrots, onion, celery, herbs and spices. You don’t need to be too particular, just cover the bird with water and cook it on low for at least four hours until the remaining meat falls off the bone. As it cooks, particularly if there is a lot of skin, you will notice a different liquid on the surface. This is poultry fat or schmaltz. As you observe, ask:
- Why does it float on top? If you have ever made a salad dressing with oil and vinegar, you know that oil will float on other liquids. This is because oil is less dense than water.
- Why does skin have so much fat? Fats and oils repel other liquids. If we didn’t have a lot of fat in our skin, we would melt in water.
Strain the stock and put it in the refrigerator. Something strange will happen with the liquid after it sets in the fridge overnight. The clear soup will turn into Thanksgiving–flavored gelatin! This will generate a few more interesting questions:
- Why does this happen? The soup thickens because of dissolved collagen. Collagens help keep our skin flexible. Collagen also keeps our joints, muscles and organs all where they are supposed to be. It is part of the “glue” that keeps our bodies together. When you add hot water, some of that stuff dissolves.
- Is it ok to eat? Yes, it is. It is very similar to the process used to make gelatin. This thick stuff can add body and flavor to soups, stuffing and anything else that calls for liquid to be added.
- What happens to the stuff when it heats back up? It will dissolve back into a liquid. In this liquid form, it can be used for cooking rice or beans.
After you make the stock, you can examine the bare skeleton of the turkey. Try to put the pieces back together and figure out how the bird moved when it was alive. How did it walk? How did it fly? How are the bones of a turkey different from human bones? What exactly is the wishbone? What does it do? If you have beef or pork bones, compare them to poultry bones.
Have fun with your family over the holidays and enjoy science!