What Has the Most Vitamin C?
Talk It Over
Vitamin C is important to good health. Among other things, it helps fight off colds and flu. Which fruit juices should you drink to get the most vitamin C?
- Pot and stove
- Measuring spoons
- Measuring cup
- Water glasses
- Iodine solution* and a dropper
- Dropper that measures in milliliters*
- Some juices to test (pineapple, apple, grapefruit, orange, lemon, and so on)
- Paper cups
- Spoons for stirring
- Get an adult to do the cooking for you. Boil 4 cups of water in a pot. Add ¼ teaspoon cornstarch and stir to dissolve. Allow this solution to cool completely before going on to step 2.
- Measure ¼ cup of the cornstarch and water mixture into a water glass. Add 8 drops of iodine. Stir. The mixture will turn dark blue.
- Put some of the juice you want to test into a paper cup. Pull some of the juice into the milliliter dropper. Watching amounts carefully, start adding juice to the blue mixture 1 milliliter at a time. Count and keep track of the number of milliliters you add. Stir after every addition and look closely at the blue color. When it disappears, stop adding juice. Record the total number of milliliters of juice needed to get rid of the blue.
- Repeat steps 2 and 3 for each juice you want to test. Always use clean glasses and spoons.Wash and dry your milliliter dropper between each test.
- This experiment works because iodine molecules and starch molecules hook together in solution, causing the blue color. Vitamin C breaks them apart. So the more milliliters of a juice you add to make the blue disappear, the less vitamin C the juice contains.
Make sure an adult does the cooking for you. Let the starch solution cool before you use it. Don't drink the iodine or the test solutions. If you get them on your skin, wash with soap and water. Don't get them on your clothes, because they will stain.
Following the "Go" procedure, test pineapple juice and apple juice only.
Perform three tests for each juice and average the results. Then use a standard solution that will let you determine exactly how much vitamin C is in each juice. To make your standard, crush a 250-milligram vitamin C tablet. Dissolve it in 250 milliliters (1 cup) of water. The concentration of your standard is then 250 milligrams/250 milliliters, or 1 mg/ml. Then follow the "Go" procedure, using the standard instead of a juice. This tells you how many milligrams of vitamin C you need to make the blue disappear. You can then calculate the milligrams of vitamin C in each of your juices using this formula:
ml of standard (needed to remove blue) ÷ ml of juice = mg of vitamin C per ml of juice
For example, if you needed 10 milliliters of the standard to get rid of the blue, and it took 20 milliliters of a juice to do it, the concentration of vitamin C in the juice is 10/20 or 0.5 mg/ml.
To expand your project, find out how heat, light, or storage time affects vitamin C content. Compare real juices with prepared soft drink mixes or canned sodas; or compare fresh or canned juices with frozen concentrates prepared according to the directions on the package.