Turn your kitchen into a laboratory as you explore the chemistry of food! Food comes in so many shapes, textures, colors, and delicious flavors, but it all serves one purpose: to give your body the nutrition it needs to survive. Different foods provide different nutrients, like vitamin C, carbohydrates, and lipids. Can you figure out what you’re getting from your favorite food? Use these three simple chemistry tests to sleuth it out. (Note: Adult supervision required when working with chemicals.)

Science Project Video – Vitamin C

What You Need:

Stop the Scurvy – Vitamin C Test

What foods have vitamin C? Do oranges have more than lemons? Do a simple chemistry test to find the answer.

>> Check out our project video to see the test in action!

  1. Choose several different things to test for vitamin C: tomato juice, orange juice, lemon juice, mango, kiwi, etc. You may also choose a food product that says it has vitamin C added. (If it is a solid, grind it up and mix with water to make a solution.)
  2. Make some indophenol solution by combining a small amount (less than 1/8 teaspoon) with 1 cup of water. Stir until it is well mixed.
  3. Put 15 drops of indophenol solution into a test tube.
  4. Add one of the juices you chose to the indophenol drop by drop. Record how many drops it takes to turn the blue indophenol colorless.
  5. Repeat with the other juices and compare the number of drops of each that you added. 3

Vitamin C is a vital nutrient for humans that aids our immune system and helps prevent disease. Many animals can make their own vitamin C, but humans must get it from their diet, which is why the vitamin C content of the food we eat is important. At one time a disease called scurvy was common among sailors, because they had no access to fruits and vegetables at sea. Scurvy is caused by a lack of vitamin C.

Indophenol is an indicator that turns colorless in the presence of vitamin C. The fewer drops of juice you need for the color change, the higher the vitamin C content in the juice. Which fruits had the most vitamin C? Do you think different preserving methods (canning, drying, freezing) has an effect on vitamin C? Do some more tests to find out!

Sugar and Starch – Glucose Test

A glucose test using Benedict

  • Fill two test tubes with an inch of Benedict’s solution each. To one add 15 drops of the saltine-and-water solution, to the other add the saltine-and-saliva solution. (Use two different pipets and label the test tubes so you can tell them apart.)
  • Fill a glass with boiling water and then set the test tubes in it and wait for three minutes. Remove the test tubes from the hot water and allow them to cool. Swirl the contents and observe the color of the liquid. Is there a difference between the two?

Glucose is a simple sugar (carbohydrate) that plants produce by the process of photosynthesis. It is the primary source of energy for our body’s cells, and is able to enter our bloodstream quickly to provide energy right away. Without glucose, our bodies wouldn’t function! Plants store extra glucose in a more complex carbohydrate called starch. During digestion, our bodies break the starch back down into glucose for our cells to use as an energy source.

In this project you saw that process in action. Saltine crackers have lots of starch. When you chewed one of the crackers, an enzyme in your saliva, called amylase, started to break the starch down into glucose. Benedict’s solution is a glucose indicator that changes colors based on how much glucose is present. Green, yellow, orange, or red indicates the presence of glucose. The color difference in your two test tubes proves that the chewed-up cracker contained glucose while the other didn’t.

Looking for Lipids – Fat Test

Test for lipids with a brown paper bag

  • Cut off the side of a brown paper bag so you have a sheet of brown paper.
  • Make solutions of several different foods you want to test for lipids. (You can try milk, peanut butter, yogurt, bread, etc.) Mix 1/2 teaspoon of ground food with 1 teaspoon water.
  • Use a permanent marker to divide the brown paper into several sections and label each section with the name of one of the foods, as in the picture on the right.
  • Put three drops of each food solution on the paper in its section. Use a clean pipet for each test. Also, test water in one section to show the result with a substance that doesn’t have any lipids.
  • Wait a few minutes until the liquid has evaporated. Hold up the paper to the light and look at each spot. The foods that contain lipids will leave a greasy mark that turns the brown paper translucent. Which foods have lipids? Are some of the greasy spots bigger than others?

Lipids are fats and oils, made of molecules that don’t dissolve in water. They are very important for our body functions because they transport vitamins, help form cell walls, and store energy long-term. Eating too much fat can be very unhealthy, but every good diet will contain a moderate amount. How many of the foods you tested contained lipids? Try comparing food that has a “regular” version and a “low-fat” (or “non-fat”) version. Is there a difference between the spots left by skim milk and whole milk?