Blue Bread

You can use the element iodine to test whether different foods contain starch. Starch is found in foods made from grain, in potatoes, and in some other things you eat. Starch is a kind of carbohydrate, or "carb", that your body uses for energy. Some people believe that you shouldn't eat carbohydrates because they are bad for you, but most nutritionists say that you should consume many different kinds of food.

But aside from that, how can iodine be used to test for starch? Easy - when iodine comes in contact with starch, it turns dark blue!

What you'll need:
Plastic or paper plate
Iodine tincture (not decolorized) or betadine solution (both are sold in drugstores)
Eye dropper (may come with the bottle of iodine)
Knife (be careful!)
Different kinds of food, such as bread, apple, pasta, tortilla, lettuce, carrot, banana, potato, sugar, salt

Place a small piece of each food on the plate. Put a drop of iodine solution onto each. What do you see?

Any of the food that turned dark blue or purple contains starch. The others don't. Simple! Throw all the pieces of food away when you're done.

Here's an extension of the experiment that you can also try. Test a small piece of a bread slice with iodine. Does it contain starch? Now chew the rest of the slice (NOT the part you tested) for a few minutes. Spit it out onto the plate and test again. Does it still contain starch? Dr. B apologizes for the fact that this experiment is a little disgusting, but sometimes you have to get grossed out for science! You will find that the original bread does contain starch, but that the chewed bread doesn't! Your saliva (spit) contains enzymes that start digesting the bread in your mouth, turning the starch into sugar.