Life Science Curriculum K-7
Submitted by: Sarah Hendry
Institution: Azusa Pacific University
Title of Experiment: Nutrition: A Study of Starches and Fats
For Starch test:
Iodine solution with dropper
Several different types of food to test for starch: ex. bread, crackers, potatoes, ripe fruit vs. unripe fruit.
For Fat test:
Brown paper bag
Different foods to test for fats: bacon, cheese, butter, potato chips,
Scientific Background of Experiment:
Nutrition is a very important part of our lives. Its certainly more fun to eat what we want, but is it very good for us? Did you ever notice how sleepy you feel after you eat a meal that is full of carbohydrates? Foods are broken down into three basic categories: proteins, carbohydrates, and fats. It is very important when you eat to eat some of all three types. Carbohydrates are can be broken down into simple sugars. When there are a whole bunch of sugars together they are called starches. Examples of starches are breads, pastas and cereals. Proteins are meats, cheeses and eggs. Some fats are butter and oil. Fats are usually mixed in with other foods. When you hear about fats, you usually think that they are bad, but they are only bad when you eat an excess of them. But did you know that fats are an important part of your diet? Did you know that every cell in your body has fat as its boundary? Fats are also used in hair and nail growth. Fats are also used as energy. Fats are more energy efficient than carbohydrates are, but carbohydrates are also very important to use as energy, because they are more readily available. Proteins are important because they provide what are called amino acids. Amino acids are needed for growth and repair of body cells. Proteins are also used for energy. There isn't one type of protein that provides all the types of amino acid that are needed in our bodies, so it's a good idea to eat different types of proteins.
For the starch test, you first need to do a control so the students can tell by looking what foods have starch and which ones don't.
1. Place some Cornstarch on a piece of wax paper. Then put a couple drops of iodine solution on the cornstarch and observe the color. Iodine turns purple/black when combined with starch.
2. Do the same for another control without starch; substitute white chalk for the cornstarch. Since there is no starch, the color should be red/brown.
3. Then repeat step #1 for any foods that you would test for starch. Compare with the controls.
For the Fat test, you also need to make controls to compare with your food samples
1. Spread oil on a brown paper bag. The paper bag should readily absorb the oil and any type of fat.
2. Spread water on a brown paper bag. The water should roll off the bag and not be absorbed.
3. Repeat step #1 with the food samples. Compare with the controls. Foods that are liquids can be rubbed onto the paper bags. All might show a wet spot on the paper bag, but if you allow the spot to dry, you can tell if it is fat or not.
Misc. Helpful Information/ Hints/ Suggestions:
Do not use whole milk for the fat test, because milk has been homogenized and the fat molecules have been dispersed and the milk will act like water, by rolling off the bag. This test should work for many types of food, so feel free to use any types of food that you want, or if your students are curious about certain foods.
Gega, P.C. and J.M. Peters. 1998. Science in Elementary Education. Prentice-Hall, Inc.
McFadden, C.H. and W.T. Keeton. 1995. Biology: An Exploration of Life. W.W. Norton