Foods may contain protein, fat, sugar or starch. Both sugar and starch are classified as carbohydrates (a line of carbon atoms with hydrogen atoms stuck to them) but starch molecules are much longer than sugar molecules. You can test for the presence of starch molecules in foods by using iodine as an indicator.
Things You'll Need
- Sample foods to test
- Washable plate or tray
- Tincture of iodine (available from online science supply stores)
Gather a number of food samples. Try to use a wide variety: fruits, vegetables, breads, cereals, dairy products and "junk" foods such as candy or chips.
Put a sample of each food on a washable plate or tray.
Fill the eyedropper with iodine and drop a few drops onto each food sample.
Observe what happens to the drops of iodine on the food. If the food contains starch, the iodine drops will turn black. If the food does not contain starch, the drops will stay the same color (reddish-orange).
Discard the samples when you are done with them. Do not let anyone eat them, as iodine is toxic.