In this Issue:
Your kitchen is a great place to study science! Cooking involves chemical reactions that combine molecules in a mixture, or change them through chemical reactions. When you eat the tasty food you've cooked, your body performs another series of chemical reactions allowing the nutrients in the food to nourish you. It is an amazing process: read on to find out how our bodies interact with different foods. Then try out some kitchen science experiments!
Carbohydrates, fats, and proteins are the main nutrients that provide our bodies with energy. (Vitamins and minerals are also important, as they are helpful to chemical processes.) Carbohydrates, including sugars and starches, are the main provider of energy. Protein is important for building and repairing tissues, especially muscles. Fats also build tissue, manufacture cell membranes, and carry vitamins like A and D. A well-balanced diet includes all of these nutrients in some form.
Carbohydrates are carbon, hydrogen, and oxygen compounds. Simple carbohydrates (sugars like fructose, lactose, and sucrose) don't have vitamins or minerals; they are "empty carbs" that just give you a jolt of energy. Complex carbohydrates (starches) contain vitamins, minerals, and sometimes fiber, which is plant material that doesn't get broken down during digestion. (Fiber helps clear your digestive system.) Although some diets are low-carb, your body usually needs carbohydrates to work properly. Your brain, for instance, needs the sugar glucose in order to function. Potatoes, rice, fruits, vegetables, and bread are good sources of carbs.
Every living cell contains protein, and it is the main component of your muscles, organs, and glands. Proteins are complex molecules, built with amino acids. Your body produces some of these, but there are also some essential amino acids that you can only get through food. You need all of these amino acids if your body is going to work properly. Some foods have only incomplete proteins; they don't contain all of the essential amino acids. It is a good idea to combine these foods with others than will provide the rest of the amino acids you need (rice, for example, is an incomplete protein, but you can "complete" it by adding beans).
Since proteins don't get stored in your body, you have to regularly eat enough of them for your body to use in building muscle and other tissue. Too little protein can result in stunted growth. Lack of protein can also cause edema, a condition where water leaks into tissue resulting in swelling of hands, feet, and bellies. (This is the reason starving children sometimes have protruding bellies.)
Fats are an important high-energy source for the body. They provide fatty acids that are necessary for many body functions, including controlling blood pressure and clotting, transporting vitamins through the bloodstream, maintaining body temperature, and building healthy cells. Fats are especially essential for the growth and development of babies. Your body stores the fat that you don't use, so eating too much can result in obesity and other health problems. Fats are usually found in meat and dairy products, but many plants turn carbohydrates into fat and store them in seeds (peanuts are a good example).
Carbohydrates, proteins, and fats all provide your body with energy, but you also need vitamins and minerals to help use that energy. Vitamins are chemical compounds and minerals are chemical elements (you can find them on a periodic table). Vitamins are necessary for some chemical reactions inside us. Among other things, they help make our bones, skin, and hair healthy, as well as strengthening our immune system. Our bodies also use many minerals in tiny amounts; for example, iron is used in making hemoglobin, which carries oxygen through our blood.
Malnutrition is an imbalance between a body's nutrient intake and the energy it needs to function. It is still a major cause for child deaths in developing countries, especially in Asia and sub-Saharan Africa.
Kitchen Science Projects
Your kitchen makes a great laboratory! Learn about chemistry and biology topics as you explore there. And if you're looking for a science fair project idea, your kitchen is a great place to start. Most of these projects take about a week before you see any results.
Dissolve an Eggshell
Make an egg shell disappear without touching it! Set a raw egg in a glass of white vinegar (acetic acid), so that it's completely covered in the liquid. Bubbles should start to form on the surface of the egg almost immediately. Let it sit for a week and then carefully take the egg out. What happened? The acid "ate" away and dissolved the calcium carbonate that the shell is made out of! There might be some chalky white residue left on the egg that you can gently scrape off. The inside of the egg is still intact, though, because vinegar doesn't break down the egg membrane. The egg also swells up, because some of the liquid seeps inside it. You should be able to see the yellow yolk through the membrane. How does the shell-less egg feel? Pick it up carefully to avoid popping it.
You can also try the experiment with a peeled boiled egg (boil it for 10 minutes). What do you expect to happen? The vinegar actually doesn't eat up the egg, but makes it feel somewhat rubbery. You can also try this with chicken bones. After a week in vinegar, the bones will be rubbery, because they lost calcium and other hardening minerals.
Avast, you scurvy knave! Scurvy is a disease caused by vitamin C deficiency. British sailors, who were away at sea for months at a time, often got it because they had a diet low in vitamins. A Scottish doctor, James Lind, suggested in the mid-1700s that fruits and vegetables would prevent scurvy. By the end of that century, the British Navy had adopted the practice of giving its sailors doses of citrus juice (which was probably the basis for the nickname "Limey").
Bacteria boom. Our bodies need good bacteria in our digestive systems. They fight pathogenic (disease-causing) bacteria, help break down food, and produce vitamin K and some B vitamins. These important jobs require large numbers of bacteria--there are over 100 trillion bacteria in your intestines. All together they weigh about 3 pounds!
Make your own ginger ale in just two days with this easy-to-follow recipe.
Find calorie amounts and nutritional value of foods in this database.
The Exploratorium's Science in the Kitchen has fun real-life applications of science and cooking.